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1

/q-exponential, Weibull, and /q-Weibull distributions: an empirical analysis  

NASA Astrophysics Data System (ADS)

In a comparative study, the /q-exponential and Weibull distributions are employed to investigate frequency distributions of basketball baskets, cyclone victims, brand-name drugs by retail sales, and highway length. In order to analyze the intermediate cases, a distribution, the /q-Weibull one, which interpolates the /q-exponential and Weibull ones, is introduced. It is verified that the basketball baskets distribution is well described by a /q-exponential, whereas the cyclone victims and brand-name drugs by retail sales ones are better adjusted by a Weibull distribution. On the other hand, for highway length the /q-exponential and Weibull distributions do not give satisfactory adjustment, being necessary to employ the /q-Weibull distribution. Furthermore, the introduction of this interpolating distribution gives an illumination from the point of view of the stretched exponential against inverse power law (/q-exponential with /q>1) controversy.

Picoli, S.; Mendes, R. S.; Malacarne, L. C.

2003-06-01

2

Using Weibull Distribution Analysis to Evaluate ALARA Performance  

SciTech Connect

As Low as Reasonably Achievable (ALARA) is the underlying principle for protecting nuclear workers from potential health outcomes related to occupational radiation exposure. Radiation protection performance is currently evaluated by measures such as collective dose and average measurable dose, which do not indicate ALARA performance. The purpose of this work is to show how statistical modeling of individual doses using the Weibull distribution can provide objective supplemental performance indicators for comparing ALARA implementation among sites and for insights into ALARA practices within a site. Maximum likelihood methods were employed to estimate the Weibull shape and scale parameters used for performance indicators. The shape parameter reflects the effectiveness of maximizing the number of workers receiving lower doses and is represented as the slope of the fitted line on a Weibull probability plot. Additional performance indicators derived from the model parameters include the 99th percentile and the exceedance fraction. When grouping sites by collective total effective dose equivalent (TEDE) and ranking by 99th percentile with confidence intervals, differences in performance among sites can be readily identified. Applying this methodology will enable more efficient and complete evaluation of the effectiveness of ALARA implementation.

E. L. Frome, J. P. Watkins, and D. A. Hagemeyer

2009-10-01

3

Weibull Analysis Handbook.  

National Technical Information Service (NTIS)

This handbook is intended to provide instructions on how to do Weibull analysis. It will provide an understanding of Weibull analysis that is common between the military and industry. The handbook contains seven chapters plus an appendix. The chapters are...

C. H. Medlin G. L. Reinman J. E. Breneman R. B. Abernethy

1983-01-01

4

Geometric theory for Weibull's distribution  

NASA Astrophysics Data System (ADS)

Weibull's distribution is the principal phenomenological law of relaxation in the physical sciences and spans three different relaxation regimes: subexponential (“stretched exponential”), exponential, and superexponential. The probabilistic theory of extreme-value statistics asserts that the linear scaling limits of minima of ensembles of positive-valued random variables, which are independent and identically distributed, are universally governed by Weibull's distribution. However, this probabilistic theory does not take into account spatial geometry, which often plays a key role in the physical sciences. In this paper we present a general and versatile model of random reactions in random environments and establish a geometry-based theory for the universal emergence of Weibull's distribution.

Eliazar, Iddo

2012-09-01

5

Optimized Estimation of the Weibull Distribution Parameters.  

National Technical Information Service (NTIS)

The report compares the accuracy of different methods for determining the Weibull distribution parameters. A bias corrected maximum likelihood estimation method is presented, and it is proposed that the method be used for analysis of brittle materials. (C...

K. Wallin

1989-01-01

6

Optimized Estimation of the Weibull Distribution Parameters.  

National Technical Information Service (NTIS)

The accuracy of different methods for determining the Weibull distribution parameters are compared. The Weibull distribution is extensively used in analyzing brittle materials such as ceramics. Usually the distribution is fitted to data sets based on less...

K. Wallin

1989-01-01

7

Sequential Tests Under Weibull Distribution.  

National Technical Information Service (NTIS)

The objective of this paper is to develop acceptance procedures based on a sequential probability ratio test when the system failures follow Weibull probability distribution. The acceptance procedures in both Military Handbook 108 and Mil-Std-781C are bas...

P. M. Ghare

1980-01-01

8

Variation RLC model of interconnect based on weibull distribution  

Microsoft Academic Search

Based on Weibull distribution, a statistical RLC model considering process variations for the efficient analysis interconnect delay is proposed. The statistical RLC model can be used for optimizations, like placement, interconnect synthesis and static timing analysis (STA). Although some delay models of interconnect have been presented, like Elmore, equivalent Elmore, D2M and WED, some of them have not considered the

Li Jianwei; Yang Yintang; Dong Gang; Wang Zeng

2009-01-01

9

Inferential Procedures for the Weibull and Generalized Gamma Distributions.  

National Technical Information Service (NTIS)

The report is concerned primarily with two general topics, the development of statistical procedures for the two-parameter and three-parameter Weibull distributions based on maximum likelihood estimators, and a study of the properties of the Weibull distr...

C. E. Antle L. J. Bain

1970-01-01

10

SPRT for Weibull distributed integrated circuit failures  

NASA Astrophysics Data System (ADS)

In this paper, we propose a sequential probability ratio test based on a two parameter Weibull distribution for IC failures. The shape parameter of the Weibull distribution characterizes the decreasing, constant and the increasing failure rate regions in the bath tub model for ICs. The algorithm detects the operating region of the IC based on the observed failure times. Unlike the fixed-length test, the proposed algorithm due to its sequential nature uses the minimum average number of devices for the test for fixed error tolerances in the detection procedure. We find that the proposed test is on an average 96 percent more efficient than the fixed-length test. Our algorithm is shown to be highly robust to the variations in the model parameters unlike other existing sequential tests. Further, extensive simulations are used to validate the analytic results of the sequential test.

Chandramouli, Rajarathnam; Vijaykrishnan, N.; Ranganathan, N.

1998-08-01

11

Analysis of CFAR performance in Weibull clutter  

NASA Astrophysics Data System (ADS)

Recent interest has focused on order statistic-based (OS-based) algorithms for calculating radar detection thresholds. Previous analyses of these algorithms are extended, to determine closed-from approximations for the signal-to-clutter ratio required to achieve a particular probability of detection in clutter environments whose amplitude statistics are modeled by the Weibull distribution, and where the clutter dominates receiver noise. Performance is evaluated in both homogeneous and inhomogeneous clutter. The analysis shows that the OS-based algorithm is quite robust against both interference clutter edges. A method is suggested for improving performance at clutter inhomogeneities for short-range targets.

Rifkin, R.

1994-04-01

12

Performance Analysis of MLP-Based Radar Detectors in Weibull-Distributed Clutter with Respect to Target Doppler Frequency  

Microsoft Academic Search

In this paper, a Multilayer Perceptron (MLP) is proposed as a radar detector of known targets in Weibull-distributed clutter.\\u000a The MLP is trained in a supervised way using the Levenberg-Marquardt backpropagation algorithm to minimize the Mean Square\\u000a Error, which is able to approximate the Neyman-Pearson detector. Due to the impossibility to find analytical expressions of\\u000a the optimum detector for this

Raul Vicen-bueno; Maria P. Jarabo-amores; Manuel Rosa-zurera; Roberto Gil-pita; David Mata-moya

2007-01-01

13

Moment estimators for the 3-parameter Weibull distribution  

Microsoft Academic Search

Weibull moments are defined generally and then calculated for the 3-parameter Weibull distribution with non-negative location parameter. Sample estimates for these moments are given and used to estimate the parameters. The results of a simulation investigation of the properties of the parameter estimates are discussed briefly. A simple method of deciding whether the location parameter can be considered zero is

G. W. Cran

1988-01-01

14

A Computer Program for Fitting Censored Samples to a Weibull Distribution (CENWEIB).  

National Technical Information Service (NTIS)

The Censored Weibull Program (CENWEIB) is a UNIVAC 1108 computer program for fitting censored samples to a Weibull distribution or for generating random data from a Weibull distribution. Maximum likelihood estimating equations are used to calculate parame...

J. Thomas J. Gallo

1978-01-01

15

Bayes Analysis and Comparison of Accelerated Weibull and Accelerated Birnbaum–Saunders Models  

Microsoft Academic Search

Several models are proposed in the literature for modeling fatigue data resulting from materials subject to cyclic stress and strain. Accelerated Weibull and accelerated Birnbaum–Saunders distributions are most commonly used models. Whereas the accelerated Weibull model is easier compared to accelerated Birnbaum–Saunders, it fails to represent the situation equally well. The present article focuses on Bayes analysis of the two

S. K. Upadhyay; Bhaswati Mukherjee

2009-01-01

16

Progressively Censored Reliability Sampling Plans for the Weibull Distribution  

Microsoft Academic Search

This article presents progressively censored variable sampling plans for the Weibull distribution. Approximate maximum likelihood estimators are developed for estimating the parameters of interest. In the construction of sampling plans, asymptotic distribution theory is used to determine the sample size and the acceptance constant. Sampling plans are tabulated for selected progressive censoring patterns and specifications, for demonstration and comparison. A

Uditha Balasooriya; Sutaip L. C. Saw; Veeresh Gadag

2000-01-01

17

Lognormal and Weibull accelerated life test plans under distribution misspecification  

Microsoft Academic Search

In this article, we derive expressions for the asymptotic distribution of maximum likelihood estimators of model parameters in accelerated life tests (ALTs) when the model distribution is misspecified. We investigate results for two popular models, namely, the lognormal and Weibull Arrhenius-type ALT models. We propose test plan criteria based on asymptotic bias (ABias) and asymptotic mean squared error (AMSE) to

Francis G. Pascual; Grace Montepiedra

2005-01-01

18

Modified Weibull distribution for maximum and significant wave height simulation and prediction  

Microsoft Academic Search

Calibration coefficients incorporated in the modified Weibull distribution are more effective for maximum wave height simulation. The parametric relations are derived there from to estimate various wave height statistics including extreme wave heights. The characteristic function of the Weibull distribution is derived. The Weibull distribution is suggested for the newly defined significant wave height simulation by the method of characteristic

G. Muraleedharan; A. D. Rao; P. G. Kurup; N. Unnikrishnan Nair; Mourani Sinha

2007-01-01

19

Limited failure-censored life test for the Weibull distribution  

Microsoft Academic Search

When the distribution of lifetimes is 2-parameter exponential, Balasooriya (1995) provided a failure-censored reliability sampling plan to save test time. This paper extends the Balasooriya sampling plan to the Weibull distribution and provides a limited failure-censored reliability sampling plan (LFCR) to do life testing when test facilities are scarce. The s-expected test time of the LFCR is computed, and the

Jong-Wuu Wu; Tzong-Ru Tsai; Liang-Yuh Ouyang

2001-01-01

20

Application of Weibull model for redefined significant wave height distributions  

Microsoft Academic Search

It is well accepted that the parent distribution for individual ocean wave heights follows the Weibull model. However this\\u000a model does not simulate significant wave height which is the average of the highest one-third of some ‘n’ (n- varies) wave heights in a wave record. It is now proposed to redefine significant wave height as average of the highest one-third

G. Muraleedharan; N. Unnikrishnan Nair; P. G. Kurup

1999-01-01

21

Weibull parameters for wind speed distribution in Saudia Arabia  

Microsoft Academic Search

The shape and scale parameters of a Weibull density distribution function are calculated for 10 locations in Saudi Arabia. The daily mean wind speed data from 1970 to mid-1990 are used for this purpose. It is found that the numerical values of the shape parameter vary between 1.7 and 2.7, whereas the value of the scale parameter is found to

S. Rehman; T. O. Halawani; T. Husain

1994-01-01

22

A new generalization of Weibull distribution with application to a breast cancer data set  

PubMed Central

SUMMARY In this article, we propose a new generalization of the Weibull distribution, which incorporates the exponentiated Weibull distribution introduced by Mudholkar and Srivastava [1] as a special case. We refer to the new family of distributions as the beta-Weibull distribution. We investigate the potential usefulness of the beta-Weibull distribution for modeling censored survival data from biomedical studies. Several other generalizations of the standard two-parameter Weibull distribution are compared with regards to maximum likelihood inference of the cumulative incidence function, under the setting of competing risks. These Weibull-based parametric models are fit to a breast cancer dataset from the National Surgical Adjuvant Breast and Bowel Project (NSABP). In terms of statistical significance of the treatment effect and model adequacy, all generalized models lead to similar conclusions, suggesting that the beta-Weibull family is a reasonable candidate for modeling survival data.

Wahed, Abdus S.; Luong, The Minh; Jeong, Jong-Hyeon

2011-01-01

23

Generalized Boltzmann factors induced by Weibull-type distributions  

NASA Astrophysics Data System (ADS)

The inverse Mellin transform technique is utilized to obtain closed form representations of the generalized Boltzmann factors associated with several Weibull-type models such as the generalized gamma, Maxwell, Rayleigh and half-normal distributions. The results complement those already available in the Physics literature in connection with the distribution of certain variables affecting the behavior of nonequilibrium systems subject to complex dynamics, which include for instance computable expressions for the generalized Boltzmann factors induced by the gamma, F, uniform and lognormal statistical models.

Mathai, A. M.; Provost, Serge B.

2013-02-01

24

Estimators and Tests based on Likelihood Depth for Copulas and the Weibull-Distribution  

Microsoft Academic Search

New estimators based on the likelihood depth for the examples of 2-dimensional, one-parametric Gumbel-Copula (and 2-dimensional Gauss-distribution) and in a second step for the Weibull- distribution are presented. The copula model has a variety of applications because it models dependence structures, e.g. in nance, in the analysis of credit risks. Copulas can also be used in the simulation of technical

Liesa Denecke; Christine Muller

25

Bayesian life test planning for the Weibull distribution with given shape parameter  

Microsoft Academic Search

This paper describes Bayesian methods for life test planning with Type II censored data from a Weibull distribution, when the Weibull shape parameter is given. We use conjugate prior distributions and criteria based on estimating a quantile of interest of the lifetime distribution. One criterion is based on a precision factor for a credibility interval for a distribution quantile and

Yao Zhang; William Q. Meeker

2005-01-01

26

Weibull-distributed radar clutter reflected from sea ice  

NASA Astrophysics Data System (ADS)

Sea-ice clutter was measured using an X-band radar which is located at the city of Mombetsu in Hokkaido. The pulse width of the radar was 80 ns. To sample at 40 ns and record digitally, an emitter-coupled logic (ECL) was used as a high-speed IC. The sampled data were first transferred to a 64-kbyte dynamic-memory board and then to a 5-inch floppy disk through an 8-bit microcomputer. These data were processed by a 16-bit microcomputer. As a result, it is shown that the amplitude of sea ice obeys a Weibull distribution with shape parameters c = 0.50-1.65. Thus the amplitude statistics deviate from the well-known Rayleigh distribution of c = 2.0, in which a logarithmic/constant-false-alarm-rate (LOG/CFAR) circuit is useful. It is concluded that the new Weibull/CFAR should be considered to suppress sea-ice clutter.

Ogawa, Hiroshi; Sekine, Matsuo; Musha, Toshimitsu; Aota, Masaaki; Ohi, Masayuki

1987-02-01

27

Weibull analysis techniques on a desktop computer  

NASA Astrophysics Data System (ADS)

This paper presents a summary of a task to provide individual U.S. Navy project engineers with analytical tools that enable them to perform Weibull failure and related analyses on a desktop computer. An integrated computer program that allows Navy analysts to perform rigorous trade-off and what-if analyses in an interactive manner without having to send the problem off to a central computer facility. The resulting computer codes exist in several forms to fit the various needs and computer configurations, such as: direct input of data, data file creation and update, and nonprinting versions for those who have no printer available. Included in the codes are three Monte Carlo routines and several test-plan generation codes.

Byers, J. L.

1988-06-01

28

Large-Scale Weibull Analysis of H-451 Nuclear-Grade Graphite Specimen Rupture Data.  

National Technical Information Service (NTIS)

A Weibull analysis was performed of the strength distribution and size effects for 2000 specimens of H-451 nuclear-grade graphite. The data, generated elsewhere, measured the tensile and four-point-flexure room-temperature rupture strength of specimens ex...

A. Walker E. H. Baker N. N. Nemeth P. L. Murthy R. L. Bratton

2012-01-01

29

Analysis of tensile bond strengths using Weibull statistics.  

PubMed

Tensile strength tests of restorative resins bonded to dentin, and the resultant strengths of interfaces between the two, exhibit wide variability. Many variables can affect test results, including specimen preparation and storage, test rig design and experimental technique. However, the more fundamental source of variability, that associated with the brittle nature of the materials, has received little attention. This paper analyzes results from micro-tensile tests on unfilled resins and adhesive bonds between restorative resin composite and dentin in terms of reliability using the Weibull probability of failure method. Results for the tensile strengths of Scotchbond Multipurpose Adhesive (3M) and Clearfil LB Bond (Kuraray) bonding resins showed Weibull moduli (m) of 6.17 (95% confidence interval, 5.25-7.19) and 5.01 (95% confidence interval, 4.23-5.8). Analysis of results for micro-tensile tests on bond strengths to dentin gave moduli between 1.81 (Clearfil Liner Bond 2V) and 4.99 (Gluma One Bond, Kulzer). Material systems with m in this range do not have a well-defined strength. The Weibull approach also enables the size dependence of the strength to be estimated. An example where the bonding area was changed from 3.1 to 1.1 mm diameter is shown. Weibull analysis provides a method for determining the reliability of strength measurements in the analysis of data from bond strength and tensile tests on dental restorative materials. PMID:15109865

Burrow, Michael F; Thomas, David; Swain, Mike V; Tyas, Martin J

2004-09-01

30

Weibull analysis applied to the pull adhesion test and fracture of a metal-ceramic interface  

SciTech Connect

Various adhesion tests have been developed to measure the mechanical bonding of thin coatings deposited on substrates. In the pull test, pins that have been bonded to the coating under test are pulled with increasing force normal to the coating until the coating is pulled from the substrate. For many systems, large scatter in the data is often observed due to uncontrolled defects in the interface and the brittle nature of the pull test. In this study, the applicability of Weibull statistics to the analysis of adhesion of Ag films to vacuum sputter-cleaned zirconia was examined. Data were obtained for smooth and rough substrates for various levels of adhesion. A good fit of the data to the Weibull distribution was observed. The Weibull modulus was found to depend on the roughness of the substrate, but was insensitive to the adhesion strength.

Erck, R.A.; Nichols, F.A. [Argonne National Lab., IL (United States). Materials and Components Technology Div.; Schult, D.L. [Illinois Univ., Urbana, IL (United States)

1992-11-01

31

A Weibull distribution with power-law tails that describes the first passage time processes of foreign currency exchanges  

NASA Astrophysics Data System (ADS)

A Weibull distribution with power-law tails is confirmed as a good candidate to describe the first passage time process of foreign currency exchange rates. The Lorentz curve and the corresponding Gini coefficient for a Weibull distribution are derived analytically. We show that the coefficient is in good agreement with the same quantity calculated from the empirical data. We also calculate the average waiting time which is an important measure to estimate the time for customers to wait until the next price change after they login to their computer systems. By assuming that the first passage time distribution might change its shape from the Weibull to the power-law at some critical time, we evaluate the averaged waiting time by means of the renewal-reward theorem. We find that our correction of tails of the distribution makes the averaged waiting time much closer to the value obtained from empirical data analysis. We also discuss the deviation from the estimated average waiting time by deriving the waiting time distribution directly. These results make us conclude that the first passage process of the foreign currency exchange rates is well described by a Weibull distribution with power-law tails.

Sazuka, Naoya; Inoue, Jun-Ichi

2007-03-01

32

Maximum likelihood estimates, from censored data, for mixed-Weibull distributions  

Microsoft Academic Search

An algorithm for estimating the parameters of mixed-Weibull distributions from censored data is presented. The algorithm follows the principle of the MLE (maximum likelihood estimate) through the EM (expectation and maximization) algorithm, and it is derived for both postmortem and non-postmortem time-to-failure data. The MLEs of the nonpostmortem data are obtained for mixed-Weibull distributions with up to 14 parameters in

Siyuan Jiang; Dimitri Kececioglu

1992-01-01

33

Suitability of the Normal, Log-normal and Weibull distributions for fitting diameter distributions of neem plantations in Northern Ghana  

Microsoft Academic Search

The suitability of the Normal, Log-normal and three-parameter Weibull probability density functions to model diameter distributions of neem (Azadirachta indica A. Juss.) grown in individual and community plantations in the Tamale Forest District was investigated. The Weibull parameters were estimated by the Maximum likelihood, Moments and Percentile methods. The maximum likelihood estimators (MLE) and moments estimators (ME) were better predictors

David M. Nanang

1998-01-01

34

Optimum simple ramp-tests for the Weibull distribution and type-I censoring  

Microsoft Academic Search

An optimum simple ramp test-accelerated life test with two different linearly increasing stresses-is presented for the Weibull distribution under type I censoring. It is assumed that the inverse power law holds between the Weibull scale parameter and the constant stress and that the cumulative exposure model for the effect of changing stress applies. The optimum plan-low stress rate and proportion

D. S. Bai; M. S. Cha; S. W. Chung

1992-01-01

35

A Discussion on Prediction of Wind Conditions and Power Generation with the Weibull Distribution  

Microsoft Academic Search

Assessment of profitability, based on the accurate measurement of the frequency distribution of wind speed over a certain period and the prediction of power generation under measured conditions, is normally a centrally important consideration for the installation of wind turbines. The frequency distribution of wind speed is evaluated, in general, using the Weibull distribution. In order to predict the frequency

Sumio Saito; Kenichi Sato; Satoshi Sekizuka

2006-01-01

36

A Bayesian life test sampling plan for products with Weibull lifetime distribution sold under warranty  

Microsoft Academic Search

A Bayesian life test sampling plan is considered for products with Weibull lifetime distribution which are sold under a warranty policy. It is assumed that the shape parameter of the distribution is a known constant, but the scale parameter is a random variable varying from lot to lot according to a known prior distribution. A cost model is constructed which

Y. I. Kwon

1996-01-01

37

Characterizing size dependence of ceramic-fiber strength using modified Weibull distribution  

SciTech Connect

The strengths of ceramic fibers have been observed to increase with decreasing fiber diameter and length. The traditional single-modal Weibull distribution function can only take into account one type of flaw, which makes it inappropriate to characterize the strength dependence of both the diameter and the length since ceramic fibers usually have both volume and surface flaws which affect the strength dependence in different ways. Although the bi-modal Weibull distribution can be used to characterize both volume and surface flaws, the mathematical difficulty in its application makes it undesirable. In this paper, the factors affecting fiber strength are analyzed in terms of fracture mechanics and flaw formation. A modified Weibull distribution function is proposed to characterize both the diameter dependence and the length dependence of ceramic fibers.

Zhu, Yuntian; Blumenthal, W.R.

1995-05-01

38

A robust approach based on Weibull distribution for clustering gene expression data  

PubMed Central

Background Clustering is a widely used technique for analysis of gene expression data. Most clustering methods group genes based on the distances, while few methods group genes according to the similarities of the distributions of the gene expression levels. Furthermore, as the biological annotation resources accumulated, an increasing number of genes have been annotated into functional categories. As a result, evaluating the performance of clustering methods in terms of the functional consistency of the resulting clusters is of great interest. Results In this paper, we proposed the WDCM (Weibull Distribution-based Clustering Method), a robust approach for clustering gene expression data, in which the gene expressions of individual genes are considered as the random variables following unique Weibull distributions. Our WDCM is based on the concept that the genes with similar expression profiles have similar distribution parameters, and thus the genes are clustered via the Weibull distribution parameters. We used the WDCM to cluster three cancer gene expression data sets from the lung cancer, B-cell follicular lymphoma and bladder carcinoma and obtained well-clustered results. We compared the performance of WDCM with k-means and Self Organizing Map (SOM) using functional annotation information given by the Gene Ontology (GO). The results showed that the functional annotation ratios of WDCM are higher than those of the other methods. We also utilized the external measure Adjusted Rand Index to validate the performance of the WDCM. The comparative results demonstrate that the WDCM provides the better clustering performance compared to k-means and SOM algorithms. The merit of the proposed WDCM is that it can be applied to cluster incomplete gene expression data without imputing the missing values. Moreover, the robustness of WDCM is also evaluated on the incomplete data sets. Conclusions The results demonstrate that our WDCM produces clusters with more consistent functional annotations than the other methods. The WDCM is also verified to be robust and is capable of clustering gene expression data containing a small quantity of missing values.

2011-01-01

39

QMPE: Estimating Lognormal, Wald, and Weibull RT distributions with a parameter-dependent lower bound  

Microsoft Academic Search

We describe and test quantile maximum probability estimator (QMPE), an open-source ANSI Fortran 90 program for response time\\u000a distribution estimation.1 QMPE enables users to estimate parameters for the ex-Gaussian and Gumbel (1958) distributions, along with three “shifted”\\u000a distributions (i.e., distributions with a parameter-dependent lower bound): the Lognormal, Wald, and Weibull distributions.\\u000a Estimation can be performed using either the standard continuous

Andrew Heathcote; Scott Brown; Denis Cousineau

2004-01-01

40

Comparison between method of moments and entropy regularization algorithm applied to parameter estimation for mixed-Weibull distribution  

Microsoft Academic Search

Mixed-Weibull distribution has been used to model a wide range of failure data sets, and in many practical situations the number of components in a mixture model is unknown. Thus, the parameter estimation of a mixed-Weibull distribution is considered and the important issue of how to determine the number of components is discussed. Two approaches are proposed to solve this

Wen-Liang Hung; Yen-Chang Chang

2011-01-01

41

A new mixed acceptance sampling plan based on sudden death testing under the Weibull distribution  

Microsoft Academic Search

In this article, a new mixed sampling plan based on the group sampling plan and sudden death testing scheme is proposed by assuming that the lifetime of the product follows the Weibull distribution. The optimal parameters of the proposed plan will be determined such that the producer's risk and consumer's risk are satisfied for specified values of acceptable and limiting

Muhammad Aslam; Muhammad Azam; Saminathan Balamurali; Chi-Hyuck Jun

2012-01-01

42

Design of progressively censored group sampling plans for Weibull distributions: An optimization problem  

Microsoft Academic Search

Optimization algorithms provides efficient solutions to many statistical problems. Essentially, the design of sampling plans for lot acceptance purposes is an optimization problem with several constraints, usually related to the quality levels required by the producer and the consumer. An optimal acceptance sampling plan is developed in this paper for the Weibull distribution with unknown scale parameter. The proposed plan

Arturo J. Fernández; Carlos J. Pérez-González; Muhammad Aslam; Chi-Hyuck Jun

2011-01-01

43

On calculating sterility in thermal preservation methods: application of the Weibull frequency distribution model  

Microsoft Academic Search

A simple and parsimonious model which originated from the Weibull frequency distribution was proposed to describe nonlinear survival curves of spores. This model was suitable for downward concavity curves (Bacillus cereus and Bacillus pumilus), as well as for upward concavity curves (Clostridium botulinum). It was shown that traditional F values calculated from this new model were no longer additive, to

P. Mafart; O. Couvert; S. Gaillard; I. Leguerinel

2002-01-01

44

Variables sampling plans for Weibull distributed lifetimes under sudden death testing  

Microsoft Academic Search

Sudden death testing can be utilized for deciding upon the lot acceptance of manufactured parts. Variables single, and double sampling plans are proposed for the lot acceptance of parts whose life follows a Weibull distribution with known shape parameter. The proposed plans are different from the existing ones in that the lot acceptance criteria do not depend on the estimated

Chi-hyuck Jun; S. Balamurali; Sang-ho Lee

2006-01-01

45

DESIGN OF FAILURE-CENSORED ACCELERATED LIFE-TEST SAMPLING PLANS FOR LOGNORMAL AND WEIBULL DISTRIBUTIONS  

Microsoft Academic Search

This paper considers the design of life-test sampling plans based on failure-censored accelerated life tests for products with lognormal and Weibull lifetime distributions. Two levels of stress higher than the use condition stress, high and low, are used. The sample size, sample proportion allocated to each stress level, and the lot acceptability constant which satisfy the producer's risk and consumer's

D. S. BAI; J. G. KIM; Y. R. CHUN

1993-01-01

46

Medium-high correlated Weibull-distributed clutter reduction by neural networks in coherent radar systems  

Microsoft Academic Search

This paper presents a clutter reduction system when medium-high correlated Weibull-distributed clutter governs the environment of a coherent radar system. This proposal is based on the capabilities of learning of some artificial intelligence techniques, such as the neural networks. This capability of learning of the neural networks is used to learn some statistical characteristics of the radar environment. The results

R. Vicen-Bueno; M. Rosa-Zurera; M. P. Jarabo-Amores; D. Mata-Moya

2009-01-01

47

Failure-censored accelerated life test sampling plans for Weibull distribution under expected test time constraint  

Microsoft Academic Search

This paper considers the design of life-test sampling plans based on failure-censored accelerated life tests. The lifetime distribution of products is assumed to be Weibull with a scale parameter that is a log linear function of a (possibly transformed) stress. Two levels of stress higher than the use condition stress, high and low, are used. Sampling plans with equal expected

J. G. Kim

1995-01-01

48

A Comparison of Accelerated Life Test Plans for Weibull and Lognormal Distributions and Type I Censoring  

Microsoft Academic Search

Previous work on planning accelerated life test plans for the Weibull and lognormal distributions has concentrated on optimum test plans that minimize the variance of some specified estimator. However, these test plans use tests at only two levels of stress and, thus, have serious practical limitations. This article compares optimum test plans and some compromise test plans with respect to

William Q. Meeker

1984-01-01

49

Call Completion Probability with Weibull Distributed Call Holding Time and Cell Dwell Time  

Microsoft Academic Search

In this paper, we derive a simple closed-form expression for the call completion probability in a wireless cellular network under Weibull distributed cell dwell time and call holding time. The derived expression is given in terms of the Meijer-G function which can be easily evaluated by commonly available computer software such as Mathematica. Numerical results are presented to show that

Suwat Pattaramalai; Valentine A. Aalo; George P. Efthymoglou

2007-01-01

50

Upper Bounds for the Power of Invariant Tests for the Exponential Distribution with Weibull Alternatives  

Microsoft Academic Search

The problem of testing for the exponential distribution (with scale, or both location and scale parameters unknown) against Weibull alternatives is considered. Upper bounds for the power of any invariant test are presented. Tests based upon the maximum likelihood estimator of the shape parameter, or a modification of it, are given which virtually achieve these bounds.

Lawrence A. Klimko; Charles E. Antle; Alfred W. Rademaker; Howard E. Rockette

1975-01-01

51

Bayes estimation of the parameters and reliability function of the 3-parameter Weibull distribution  

Microsoft Academic Search

The authors obtain Bayes estimates of the parameters and reliability function of a 3-parameter Weibull distribution and compare posterior standard-deviation estimates with the corresponding asymptotic standard-deviation estimates of their maximum likelihood counterparts. Numerical examples are given

S. K. Sinha; J. A. Sloan

1988-01-01

52

Exponentiated Weibull distribution family under aperture averaging for Gaussian beam waves.  

PubMed

Nowadays, the search for a distribution capable of modeling the probability density function (PDF) of irradiance data under all conditions of atmospheric turbulence in the presence of aperture averaging still continues. Here, a family of PDFs alternative to the widely accepted Log-Normal and Gamma-Gamma distributions is proposed to model the PDF of the received optical power in free-space optical communications, namely, the Weibull and the exponentiated Weibull (EW) distribution. Particularly, it is shown how the proposed EW distribution offers an excellent fit to simulation and experimental data under all aperture averaging conditions, under weak and moderate turbulence conditions, as well as for point-like apertures. Another very attractive property of these distributions is the simple closed form expression of their respective PDF and cumulative distribution function. PMID:22714332

Barrios, Ricardo; Dios, Federico

2012-06-01

53

A modified Weibull model for tensile strength distribution of carbon nanotube fibers with strain rate and size effects  

NASA Astrophysics Data System (ADS)

Fundamental studies on the effects of strain rate and size on the distribution of tensile strength of carbon nanotube (CNT) fibers are reported in this paper. Experimental data show that the mechanical strength of CNT fibers increases from 0.2 to 0.8 GPa as the strain rate increases from 0.00001 to 0.1 (1/s). In addition, the influence of fiber diameter at low and high strain rate conditions was investigated further with statistical analysis. A modified Weibull distribution model for characterizing the tensile strength distribution of CNT fibers taking into account the effect of strain rate and fiber diameter is proposed.

Sun, Gengzhi; Pang, John H. L.; Zhou, Jinyuan; Zhang, Yani; Zhan, Zhaoyao; Zheng, Lianxi

2012-09-01

54

Bayesian variable sampling plan for the weibull distribution with type I censoring  

Microsoft Academic Search

In this article, we study a model of a single variable sampling plan with Type I censoring. Assume that the quality of an\\u000a item in a batch is measured by a random variable which follows a Weibull distributionW (?,m), with scale parameter ? and shape parameterm having a gamma-discrete prior distribution or ?=1\\/? andm having an inverse gamma-uniform prior distribution.

Chen Jianwei; Lam Yeh

1999-01-01

55

Introduction to Weibull Statistics.  

National Technical Information Service (NTIS)

This report describes Weibull statistics with particular reference to the analysis of data obtained from mechanical tests on brittle materials. The basic equations are all derived from first principles and the construction and use of Weibull Probability G...

P. M. Braiden

1975-01-01

56

Introduction to Weibull Statistics.  

National Technical Information Service (NTIS)

Weibull statistics are described with particular reference to the analysis of data obtained from mechanical tests on brittle materials. The basic equations are all derived from principles and the construction and use of Weibull Probability Graphs are desc...

P. M. Braiden

1975-01-01

57

Dyke thicknesses follow a Weibull distribution controlled by host-rock strength and magmatic overpressure  

NASA Astrophysics Data System (ADS)

Dykes are the primary transport channels of magma through the crust and form large parts of volcanic edifices and the oceanic crust. Their dimensions are primary parameters that control magma transport rates and therefore influence, e.g. the size of fissure eruptions and crustal growth. Since the mechanics of dyke emplacement are essentially similar and independent of the tectonic setting, dyke properties should generally follow the same statistical laws. The measurement of dyke thicknesses is, of all parameters, least affected by censoring and truncation effects and therefore most accurately accessible. Nevertheless, dyke thicknesses have been ascribed to follow many different statistical distributions, such as negative exponential and power law. We tested large datasets of dyke thicknesses from different tectonic settings (mid-ocean ridge, oceanic intra-plate) for different statistical distributions (log-normal, exponential, power law (with fixed or variable lower cut-off), Rayleigh, Chi-square, and Weibull). For this purpose, we first converted the probability density functions of each dataset to cumulative distribution functions, thus avoiding arbitrariness in bin size. A non-linear, least-squares fit was then used to compute the parameter(s) of the distribution function. The goodness-of-fit was evaluated using three methods: (1) the residual sum of squares, (2) the Kolmogorov-Smirnov statistics, and (3) p-values using 10,000 synthetic datasets. The results show that, in general, dyke thickness is best described by a Weibull distribution. This suggests material strength is a function of the dimensions of included weaknesses (e.g. fractures), following the "weakest link of a chain" principle. Our datasets may be further subdivided according to dyke lithology (magma type) and type (regional dyke vs. inclined sheet), which leads to an increasingly better fit of the Weibull distribution. Weibull is hence the statistical distribution that universally describes dyke thickness, irrespective of the tectonic setting, type of magmatic sheet intrusion (e.g. regional dykes and inclined sheets), or magma type. Moreover, the Weibull distribution of dyke thickness can be easily explained by the interplay of host-rock strength (i.e. the distribution of weaknesses) and magmatic overpressure.

Krumbholz, M.; Hieronymus, C.; Burchardt, S.; Troll, V. R.; Tanner, D. C.; Friese, N.

2012-04-01

58

Mixed Weibull distributions in reliability engineering: Statistical models for the lifetime of units with multiple modes of failure  

NASA Astrophysics Data System (ADS)

The finite mixed Weibull distribution is an appropriate distribution in modeling the lifetime of the units having more than one possible failure cause. Through a change of variable, 5 parameters in a two Weibull mixture can be reduced to 3. A parameter vector (P sub 1, eta, beta) defines a family of two-Weibull mixtures which have common characteristics. Numerous probability plots are investigated on Weibull probability paper (WPP). For a given P sub 1, the eta-beta plane is partitioned into seven regions which are labeled by A through F and S. The region S represents the two Weibull mixtures whose cumulative distribution functions (CDF) curves are very close to a straight line. The regions A through F represent six typical shapes of the CDF curves on WPP, respectively. The two-Weibull mixtures in one region have similar characteristics. Three important features of the two-Weibull mixture with well separated subpopulations are proved. Two existing methods for the graphical estimation of the parameters are discussed. The expectation-maximization (EM) algorithm is successfully applied to solve the maximum likelihood estimation (MLE) for mixed Weibull distributions when m, the number of subpopulations in a mixture is known. Extensive Monte Carlo simulations are performed. The distributions of the MLE of the parameters and of the reliability of a two Weibull mixture are studied. The MLE's of the parameters are sensitive to the degree of separation of the two subpopulation probability density functions (PDF's), but the MLE of the reliability is not. The generalized likelihood ratio (GLR) test is used to determine m. A FORTRAN computer program is developed to conduct simulation of the GLR test for less than or = m sub 0 less than m sub 1 less than or = 5.

Jiang, Siyuan

1991-08-01

59

Exponentiated Weibull distribution family under aperture averaging Gaussian beam waves: comment.  

PubMed

Recently, an exponentiated Weibull distribution model was presented for describing the effects of aperture averaging on scintillation of Gaussian beams propagating through atmospheric turbulence. The model uses three parameters that are derived from physical quantities so that in principle the model could be used to predict optical link performance. After reviewing this model, however, we find several inconsistencies that render it unusable for this purpose under any scintillation conditions. PMID:23037115

Yura, H T; Rose, T S

2012-08-27

60

Average BER of free-space optical systems in turbulent atmosphere with exponentiated Weibull distribution.  

PubMed

A computationally efficient expression is presented for evaluating the average bit error rate (BER) of an intensity-modulation and direct-detection free-space optical system with on-off keying signaling technique operating in turbulent atmosphere described by the exponentiated Weibull distribution. The presented numerical results show the effects of aperture averaging on the average BER under weak and moderate turbulence conditions, and are confirmed by Monte Carlo simulations. PMID:23258032

Yi, Xiang; Liu, Zengji; Yue, Peng

2012-12-15

61

Acceptance sampling plans based on failure-censored step-stress accelerated tests for Weibull distributions  

Microsoft Academic Search

Purpose – The paper aims to present acceptance sampling plans based on failure-censored step-stress accelerated life tests for items having Weibull lives. Design\\/methodology\\/approach – The model parameters are estimated by the method of maximum likelihood. Based on asymptotic distribution theory, the sample size and the acceptability constant are determined satisfying the producer's and consumer's risks. The step-stress accelerated life test

Sang Wook Chung; Young Sung Seo; Won Young Yun

2006-01-01

62

Statistical failure analysis of metallic U-10zr\\/HT9 fast reactor fuel pin by considering the weibull distribution and cumulative damage fraction  

Microsoft Academic Search

A statistical failure analysis is performed to obtain some insight into the rupture behavior of the metallic U-10Zr\\/HT-9 fast reactor fuel pins which were irradiated in X447 subassembly of EBR-II reactor. Generally, the primary factor that contributes to metallic fuel pin failure is believed to be plenum pressure buildup due to fission gas release. However, the calculated cumulative damage fraction

Cheol Nam; Woan Hwang; Dong-Seong Sohn

1998-01-01

63

Population of Exponentially Distributed Individual Lifespans Cannot Lead to Gompertzian or to Weibull (with Increasing Mortality Rate) Dynamics.  

National Technical Information Service (NTIS)

It is well documented in the biological literature, that many species throughout the animal kingdom, exhibit Gompertizian or Weibull-like population level survival distributions. Many researches have long assumed, believed, or other wise postulated that a...

F. Guess M. Witten

1986-01-01

64

The discrete Weibull distribution: an alternative for correlated counts with confirmation for microbial counts in water.  

PubMed

Distributions of pathogen counts in treated water over time are highly skewed, power-law-like, and discrete. Over long periods of record, a long tail is observed, which can strongly determine the long-term mean pathogen count and associated health effects. Such distributions have been modeled with the Poisson lognormal (PLN) computed (not closed-form) distribution, and a new?discrete growth distribution?(DGD), also computed, recently proposed and demonstrated for microbial counts in water (Risk Analysis?29, 841-856). In this article, an error in the original theoretical development of the DGD is pointed out, and the approach is shown to support the closed-form discrete Weibull (DW). Furthermore, an information-theoretic derivation of the DGD is presented, explaining the fit shown for it to the original nine empirical and three simulated (n?= 1,000) long-term waterborne microbial count data sets. Both developments result from a theory of multiplicative growth of outcome size from correlated, entropy-forced cause magnitudes. The predicted DW and DGD are first borne out in simulations of continuous and discrete correlated growth processes, respectively. Then the DW and DGD are each demonstrated to fit 10 of the original 12 data sets, passing the chi-square goodness-of-fit test (?= 0.05, overall?p?= 0.1184). The PLN was not demonstrated, fitting only 4 of 12 data sets (p?= 1.6 × 10(-8) ), explained by cause magnitude correlation. Results bear out predictions of monotonically decreasing distributions, and suggest use of the DW for inhomogeneous counts correlated in time or space. A formula for computing the DW mean is presented. PMID:21091749

Englehardt, James D; Li, Ruochen

2010-11-22

65

Coherent Detection of Swerling 0 Targets in Sea-Ice Weibull-Distributed Clutter Using Neural Networks  

Microsoft Academic Search

The detection of Swerling 0 targets in movement in sea-ice Weibull-distributed clutter by neural networks (NNs) is presented in this paper. Synthetic data generated for typical sea-ice Weibull parameters reported in the literature are used. Due to the capability of NNs for learning the statistical properties of the clutter and target signals during a supervised training, high clutter reduction rates

Raul Vicen-Bueno; Manuel Rosa-Zurera; María-Pilar Jarabo-Amores; David de la Mata-Moya

2010-01-01

66

Weibull analyses of bacterial interaction forces measured using AFM.  

PubMed

Statistically significant conclusions from interaction forces obtained by AFM are difficult to draw because of large data spreads. Weibull analysis, common in macroscopic bond-strength analyses, takes advantage of this spread to derive a Weibull distribution, yielding the probability of occurrence of a force value and the dependability of the data set. Here we propose Weibull distribution as a new way to present nanoscopic bacterial interaction forces obtained using AFM. PMID:20399627

van der Mei, Henny C; de Vries, Joop; Busscher, Henk J

2010-03-27

67

[Weibull statistical analysis of bending strength data measured either in air or in distilled water for sintered hydroxyapatite ceramics coated on the metal substrate].  

PubMed

To assess the effects of H2O on the fracture stress of sintered hydroxyapatite (HAP) ceramics prepared by procedures similar to those used for HAP coated on the metal substrate, four-point bending tests were carried out at 0.5 mm/min either in air (20 C, R.H. 73%) or in distilled water (37 degrees C). Then, strength data obtained were analyzed using two-parameter weibull statistics. In each condition, the bending strength data gave a good fit to single-mode weibull distribution. Weibull analysis of the data gave weibull parameter m = 7.8, sigma 0 = 26.2 MPa in air and m = 8.1, sigma 0 = 18.5 MPa in distilled water, which were calculated assuming a surface flaw model. The mean value of bending strength was 27.3 MPa in air and 18.2 MPa in distilled water. These results indicated that a corrosive environment such as H2O affects fracture stress when measured at a constant stress rate. This effect is considered to be caused by slow crack growth of cracks, occurring at a loading level lower than those at which specimens will fail. Using the weibull distribution function estimated in this study, the effects of both dimension of specimen and stress distribution in the specimen on the mean fracture stress have been predicted. PMID:2135508

Wakamatsu, N; Goto, T; Adachi, M; Imura, S; Hayashi, K; Kamemizu, H; Iijima, M; Gyotoku, T; Shibata, S; Horiguchi, T

1990-03-01

68

Accelerated life test sampling plans for the Weibull distribution under Type I progressive interval censoring with random removals  

Microsoft Academic Search

This paper considers the design of accelerated life test (ALT) sampling plans under Type I progressive interval censoring with random removals. We assume that the lifetime of products follows a Weibull distribution. Two levels of constant stress higher than the use condition are used. The sample size and the acceptability constant that satisfy given levels of producer's risk and consumer's

Chang Ding; Chunyan Yang; Siu-Keung Tse

2010-01-01

69

USE OF WEIBULL FUNCTION FOR NON-LINEAR ANALYSIS OF EFFECTS OF LOW LEVELS OF SIMULATED HERBICIDE DRIFT ON PLANTS  

EPA Science Inventory

We compared two regression models, which are based on the Weibull and probit functions, for the analysis of pesticide toxicity data from laboratory studies on Illinois crop and native plant species. Both mathematical models are continuous, differentiable, strictly positive, and...

70

Reliability Estimation for the Generalized Gamma Distribution and Robustness of the Weibul Model.  

National Technical Information Service (NTIS)

Two test statistics are suggested for discriminating between exponential model and the more general Weibull or gamma models, and these are compared to some previously used test statistics by Monte Carlo methods. The results of estimating reliability under...

C. E. Antle H. W. Hager L. J. Bain

1969-01-01

71

Mixture and non-mixture cure fraction models based on the generalized modified Weibull distribution with an application to gastric cancer data.  

PubMed

The cure fraction models are usually used to model lifetime time data with long-term survivors. In the present article, we introduce a Bayesian analysis of the four-parameter generalized modified Weibull (GMW) distribution in presence of cure fraction, censored data and covariates. In order to include the proportion of "cured" patients, mixture and non-mixture formulation models are considered. To demonstrate the ability of using this model in the analysis of real data, we consider an application to data from patients with gastric adenocarcinoma. Inferences are obtained by using MCMC (Markov Chain Monte Carlo) methods. PMID:24008248

Martinez, Edson Z; Achcar, Jorge A; Jácome, Alexandre A A; Santos, José S

2013-08-06

72

Suppression of Log-Weibull Distributed Sea-Ice Clutter Using a Modified LOG/CFAR System  

NASA Astrophysics Data System (ADS)

We observed sea-ice clutter using a millimeter wave radar with a frequency 34.860 GHz, a beamwidth 0.25°, and a plusewidth 30 ns which is located at the city of Mombetsu in Hokkaido. To determine the sea-ice clutter amplitude, we introduce the Akaike Information Criterion (AIC). It is discovered that the sea-ice clutter amplitudes obey the log-Weibull distribution with the shape parameters of 2.36 to 2.93 in terms of the temporal and small scale range fluctuations with which a constant false alarm rate (CFAR) is concerned. We propose a new log-Weibull/CFAR system uses a modified cell-averaging LOG/CFAR system. It is found that sea-ice clutter is suppressed with the improvement of more than 40 dB.

Sayama, Shuji; Ishii, Seishiro; Sekine, Matsuo

73

Long-Term Profiles of Wind and Weibull Distribution Parameters up to 600 m in a Rural Coastal and an Inland Suburban Area  

NASA Astrophysics Data System (ADS)

An investigation of the long-term variability of wind profiles for wind energy applications is presented. The observations consists of wind measurements obtained from a ground-based wind lidar at heights between 100 and 600 m, in combination with measurements from tall meteorological towers at a flat rural coastal site in western Denmark and at an inland suburban area near Hamburg in Germany. Simulations with the weather research and forecasting numerical model were carried out in both forecast and analysis configurations. The scatter between measured and modelled wind speeds expressed by the root-mean-square error was about 10 % lower for the analysis compared to the forecast simulations. At the rural coastal site, the observed mean wind speeds above 60 m were underestimated by both the analysis and forecast model runs. For the inland suburban area, the mean wind speed is overestimated by both types of the simulations below 500 m. When studying the wind-speed variability with the Weibull distribution, the shape parameter was always underestimated by the forecast compared to both analysis simulations and measurements. At the rural coastal site although the measured and modelled Weibull distributions are different their variances are nearly the same. It is suggested to use the shape parameter for climatological mesoscale model evaluation. Based on the new measurements, a parametrization of the shape parameter for practical applications is suggested.

Gryning, Sven-Erik; Batchvarova, Ekaterina; Floors, Rogier; Peña, Alfredo; Brümmer, Burghard; Hahmann, Andrea N.; Mikkelsen, Torben

2013-10-01

74

Goodness-of-fit tests for type-I extreme-value and 2-parameter Weibull distributions  

Microsoft Academic Search

This study investigates the properties of the Kolmogorov-Smirnov (K-S), Cramer-von Mises (C-M) and Anderson-Darling (A-D) statistics for goodness-of-fit tests for type-I extreme-value and for 2-parameter Weibull distributions, when the population parameters are estimated from a complete sample by graphical plotting techniques (GPT). Three GPT-median ranks, mean ranks, symmetrical sample cumulative distribution (symmetrical ranks)-are combined with the least-squares method (LSM) on

Toshiyuki Shimokawa; Min Liao

1999-01-01

75

A comparative study for the location and scale parameters of the Weibull distribution with given shape parameter  

NASA Astrophysics Data System (ADS)

Nine parametric estimators of the location and scale parameters of a two-parameter Weibull distribution are compared in terms of their bias and efficiency in a simulation study. The estimators considered are the maximum likelihood estimators (MLE), moment estimators (ME), generalized spacing estimators (GSE), modified maximum likelihood estimators I (MMLE-I), modified maximum likelihood estimators II (MMLE-II), Tiku's modified maximum likelihood estimators (TMMLE), least-squares estimators (LSE), weighted least-squares estimators (WLSE) and percentile estimators (PCE). The aim of the comparisons is to identify the most efficient estimators among these nine estimators for different shape parameters and sample sizes.

Kantar, Yeliz Mert; ?eno?lu, Birdal

2008-12-01

76

Improvement in mechanical properties of jute fibres through mild alkali treatment as demonstrated by utilisation of the Weibull distribution model.  

PubMed

Chemically modified jute fibres are potentially useful as natural reinforcement in composite materials. Jute fibres were treated with 0.25%-1.0% sodium hydroxide (NaOH) solution for 0.5-48 h. The hydrophilicity, surface morphology, crystallinity index, thermal and mechanical characteristics of untreated and alkali treated fibres were studied.The two-parameter Weibull distribution model was applied to deal with the variation in mechanical properties of the natural fibres. Alkali treatment enhanced the tensile strength and elongation at break by 82% and 45%, respectively but decreased the hydrophilicity by 50.5% and the diameter of the fibres by 37%. PMID:22209134

Roy, Aparna; Chakraborty, Sumit; Kundu, Sarada Prasad; Basak, Ratan Kumar; Majumder, Subhasish Basu; Adhikari, Basudam

2011-11-30

77

A comparison of Weibull and {beta}{sub Ic} analysis of transition range fracture toughness data  

SciTech Connect

Characteristics of extremal statistics that are used to predict size effects on cleavage fracture toughness in the transition range were explored. A 533 grade B steel base and weld metals were tested using compact specimens ranging in size from {1/2}TC(T) to 8TC(T) and with sufficient replication in some cases to provide good fits to Weibull distributions. The classical specimen size effect on data scatter and median K{sup Jc} toughness at a given test temperature was observed in the low- to mid-transition range. These effects were well predicted with external statistics. However, the same model is not applicable on the lower shelf, and it also becomes extremely weak and unreliable in the mid- to high-transition range. The Irwin {beta}{sub c}{minus}{beta}{sub Ic} relationship was also explored as a model and was found to predict similar size effects. The predictive characteristics of the latter seemed better suited to deal with the diminution of size effects in the near- to low-shelf toughness range. In the rising toughness part of the transition, the predictive characteristics were about the same as the statistical model up to where {beta}{sub c} ({beta}{sub Jc} in this study) of the baseline (small specimen) data were {pi} or less. This work could be used in the establishment of a framework for transition temperature test criteria. Upper- and lower-bound {beta}{sub Jc} criteria could be used to define optimum conditions for the application of either of the aforementioned models. For surveillance programs, sensible rules should be specified as to specimen size requirements and numbers of specimens to be tested in order to apply these analytical models. Another need would be the definition of a procedure for the Weibull distribution fitting. The present report suggests items to be considered for requirements in application of these predictive techniques.

McCabe, D.E. [Oak Ridge National Lab., TN (United States)

1992-01-01

78

On changing points of mean residual life and failure rate function for some generalized Weibull distributions  

Microsoft Academic Search

The failure rate function and mean residual life function are two important characteristics in reliability analysis. Although many papers have studied distributions with bathtub-shaped failure rate and their properties, few have focused on the underlying associations between the mean residual life and failure rate function of these distributions, especially with respect to their changing points. It is known that the

M Xie; T. N Goh; Y Tang

2004-01-01

79

How to do a Weibull statistical analysis of flexural strength data: application to AlON, diamond, zinc selenide, and zinc sulfide  

NASA Astrophysics Data System (ADS)

For the purpose of assessing the strength of engineering ceramics, it is common practice to interpret the measured stresses at fracture in the light of a semi-empirical expression derived from Weibull's theory of brittle fracture, i.e., ln[-ln(1-P)]=-mln((sigma) N)+mln((sigma) ), where P is the cumulative failure probability, (sigma) is the applied tensile stress, m is the Weibull modulus, and (sigma) N is the nominal strength. The strength of (sigma) N, however, does not represent a true measure because it depends not only on the test method but also on the size of the volume or the surface subjected to tensile stresses. In this paper we intend to first clarify issues relating to the application of Weibull's theory of fracture and then make use of the theory to assess the results of equibiaxial flexure testing that was carried out on polycrystalline infrared-transmitting materials. These materials are brittle ceramics, which most frequently fail as a consequence of tensile stresses acting on surface flaws. Since equibiaxial flexure testing is the preferred method of measuring the strength of optical ceramics, we propose to formulate the failure-probability equation in terms of a characteristic strength, (sigma) C, for biaxial loadings, i.e., P=1-exp{-(pi) (ro/cm)2[(Gamma) (1+1/m)]m((sigma) /(sigma) C)m}, where ro is the radius of the loading ring (in centimeter) and (Gamma) (z) designates the gamma function. A Weibull statistical analysis of equibiaxial strength data thus amounts to obtaining the parameters m and (sigma) C, which is best done by directly fitting estimated Pi vs i data to the failure-probability equation; this procedure avoids distorting the distribution through logarithmic linearization and can be implemented by performing a non-linear bivariate regression. Concentric- ring fracture testing performed on five sets of Raytran materials validates the procedure in the sense that the two parameters model appears to describe the experimental failure-probability distributions remarkably well. Specifically, we demonstrate that the wide divergence in published CVD-diamond strength data reflects the poor Weibull modulus of this material and must be attributed to the size effect rather than the quality of the deposits. Finally, the problem of obtaining correct failure stresses from the measured failure loads is examined in the Appendix.

Klein, Claude A.; Miller, Richard P.

2001-09-01

80

Nearly unbiased estimators for the three-parameter Weibull distribution with greater efficiency than the iterative likelihood method.  

PubMed

The maximum likelihood estimation (MLE) method is the most commonly used method to estimate the parameters of the three-parameter Weibull distribution. However, it returns biased estimates. In this paper, we show how to calculate weights which cancel the biases contained in the MLE equations. The exact weights can be computed when the population parameters are known and the expected weights when they are not. Two of the three weights' expected values are dependent only on the sample size, whereas the third also depends on the population shape parameters. Monte Carlo simulations demonstrate the practicability of the weighted MLE method. When compared with the iterative MLE technique, the bias is reduced by a factor of 7 (irrespective of the sample size) and the variability of the parameter estimates is also reduced by a factor of 7 for very small sample sizes, but this gain disappears for large sample sizes. PMID:18177546

Cousineau, Denis

2008-01-03

81

Nearly Best Linear Unbiased Estimation of the Location and Scale Parameters of the Weibull Probability Distribution by the Use of Order Statistics.  

National Technical Information Service (NTIS)

Five-decimal-place tables are given for the coefficients for nearly best linear estimation of the location and scale parameters of the Weibull distribution. With the shape parameter known, the least squares method of linear estimation as applied to order ...

F. B. Stump

1968-01-01

82

A practical and systematic review of Weibull statistics for reporting strengths of dental materials  

PubMed Central

Objectives To review the history, theory and current applications of Weibull analyses sufficient to make informed decisions regarding practical use of the analysis in dental material strength testing. Data References are made to examples in the engineering and dental literature, but this paper also includes illustrative analyses of Weibull plots, fractographic interpretations, and Weibull distribution parameters obtained for a dense alumina, two feldspathic porcelains, and a zirconia. Sources Informational sources include Weibull's original articles, later articles specific to applications and theoretical foundations of Weibull analysis, texts on statistics and fracture mechanics and the international standards literature. Study Selection The chosen Weibull analyses are used to illustrate technique, the importance of flaw size distributions, physical meaning of Weibull parameters and concepts of “equivalent volumes” to compare measured strengths obtained from different test configurations. Conclusions Weibull analysis has a strong theoretical basis and can be of particular value in dental applications, primarily because of test specimen size limitations and the use of different test configurations. Also endemic to dental materials, however, is increased difficulty in satisfying application requirements, such as confirming fracture origin type and diligence in obtaining quality strength data.

Quinn, George D.; Quinn, Janet B.

2011-01-01

83

A new goodness-of-fit test for type-I extreme-value and 2-parameter weibull distributions with estimated parameters  

Microsoft Academic Search

On the basis of the Kolmogorov-Smirnov (K-S), Cramer-von Mises (C-M) and Anderson- Darling (A-D) statistics, a new statisticLn, is developed and applied for testing the goodness-of-fit of Type-I extreme-value and 2-parameter Weibull distributions with estimated parameters. Maximum likelihood estimators (MLEs) and graphical plotting techniques (GPTs) are used to estimate the population parameters from a complete sample. The critical values of

Min Liao; Toshiyuki Shimokawa

1999-01-01

84

Optimal CFAR detection in Weibull clutter  

NASA Astrophysics Data System (ADS)

Optimal, in the maximum likelihood sense, constant false-alarm rate (CFAR) detection for Weibull clutter statistics, is investigated. The proposed OW (optimal Weibull) estimator is proved to be an asymptotically efficient estimator of the mean power of the Weibull clutter. Theoretical analysis of the OW-CFAR detector is provided, while detection performance analysis is carried out using the Monte Carlo simulation method. The operation of the median and morphological (MEMO)-CFAR detector in Weibull clutter statistics is also explained. It performs almost optimally in uniform clutter and, simultaneously, it is robust in multitarget situations. The performance of the proposed OW-CFAR detector in uniform Weibull clutter is used as a yardstick in the analysis of the MEMO cell-averager (CA) and ordered statistic (OS)-CFAR detectors. Nonfluctuating and fluctuating (Swerling II) targets are considered in detection analysis. The performance of the detectors is also examined at clutter edges.

Anastassopoulos, Vassilis; Lampropoulos, George A.

1995-01-01

85

Kinetic modeling of native Cassava starch thermo-oxidative degradation using Weibull and Weibull-derived models.  

PubMed

A new approach in kinetic modeling of thermo-oxidative degradation process of starch granules extracted from the Cassava roots was developed. Based on the thermoanalytical measurements, three reaction stages were detected. Using Weibull and Weibull-derived (inverse) models, it was found that the first two reaction stages could be described with the change of apparent activation energy (Ea ) on conversion fraction (?(T)) (using "Model-free" analysis). It was found that first reaction stage, which involves dehydration and evaporation of lower molecular mass fractions, can be described with an inverse Weibull model. This model with its distribution of Ea values and derived distribution parameters includes the occurrence of three-dimensional diffusion mechanism. The second reaction stage is very complex, and it was found to contain the system of simultaneous reactions (where depolymerization occurs), and can be described with standard Weibull model. Identified statistical model with its distribution of Ea values and derived distribution parameters includes the kinetic model that gives the variable reaction order values. Based on the established models, shelf-life studies for first two stages were carried out. Shelf-life testing has shown that optimal dehydration time is achieved by a programmed heating at medium heating rate, whereas optimal time of degradation is achieved at highest heating rate. © 2013 Wiley Periodicals, Inc. Biopolymers 101: 41-57, 2014. PMID:23640748

Jankovi?, Bojan

2014-01-01

86

Some Simple Estimators for the Shape Parameter of the Weibull Laws.  

National Technical Information Service (NTIS)

Simple tabular methods of estimating the shape parameter of the Weibull distribution are derived. These estimates of the shape parameter will be further used to obtain simple estimates of the other parameters of the Weibull distribution. In many practical...

S. D. Dubey

1967-01-01

87

High weibull modulus HVOF titania coatings  

NASA Astrophysics Data System (ADS)

The mechanical behavior of high-velocity oxyfuel (HVOF) sprayed titania (TiO2) coatings was evaluated using Vickers hardness measurements on the cross section and top surface. The distribution of hardness values for the cross-section and top surface under 25, 50, 100, 300, 500, and 1000 g loads was analyzed via Weibull statistics. The coating microstructure was evaluated using scanning electron microscopy (SEM). It was observed that the microstructural features were similar in the top surface and cross-section, different from the lamellar structure commonly found in thermal spray coatings. X-ray diffraction (XRD) analysis identified rutile as the major coating phase. The in-flight sprayed particle parameters such as temperature and velocity were determined using a commercial diagnostic system based on pyrometry and time-of-flight measurements. The uniformity of the microstructure resulted in a near isotropic behavior of the mechanical properties, such as hardness, in the coating cross-section and top surface. High Weibull modulus values were observed when compared with results of other thermal spray coatings available in the literature. These initial results should contribute to a more general understanding of the conditions necessary to achieve coatings with high uniformity and assist in the engineering of coating microstructures for specific applications.

Lima, R. S.; Marple, B. R.

2003-06-01

88

Wind Speed Characteristics and Resource Assessment Using Weibull Parameters  

Microsoft Academic Search

The study utilized wind speed measurements made at three heights and the Weibull parameters to study the wind speed characteristics and assess the wind power potential of seven sites in Saudi Arabia. Weibull shape and scale parameters were estimated using maximum likelihood method. These parameters were found to fit the actual wind frequency distributions with acceptable coefficient of determination (>0.95)

S. Rehman; A. M. Mahbub; Josua P. Meyer; L. M. Al-Hadhrami

2012-01-01

89

Application of Weibull Hazard Analysis to the Determination of the Shelf Life of Roasted and Ground Coffee  

Microsoft Academic Search

Roasted and ground coffee was stored at constant O2partial pressure (0.5–21.3 kPa), aw(0.106–0.408) and temperature (4–35°C). Product acceptability was monitored by use of a modified Weibull Hazard sensory method where the end of shelf-life was the time at which 50% consumers found the product unacceptable. The effect of O2, awand temperature was studied from a kinetics standpoint. Oxygen increase from

C. Cardelli; T. P. Labuza

2001-01-01

90

Analysis of DC current accelerated life tests of GaN LEDs using a Weibull-based statistical model  

Microsoft Academic Search

Gallium-nitride-based light-emitting diode (LED) accelerated life tests were carried out over devices adopting two different packaging schemes (i.e., with plastic transparent encapsulation or with pure metallic package). Data analyses were done using a Weibull-based statistical description with the aim of estimating the effect of high current on device performance. A consistent statistical model was found with the capability to estimate

S. Levada; M. Meneghini; G. Meneghesso; E. Zanoni

2005-01-01

91

Maximum Likelihood Estimation with the Weibull Model  

Microsoft Academic Search

Some of the questions concerning the uniqueness of the maximum likelihood estimates for the parameters in the Weibull distribution are considered for both censored and noncensored samples. In some cases answers previously known are reviewed, while new results are presented for some other cases. In particular, it is shown that with the shape parameter known, the maximum likelihood estimates of

Howard Rockette; Charles Antle; Lawrence A. Klimko

1974-01-01

92

Weibull brittle material failure model for the ABAQUS computer program.  

National Technical Information Service (NTIS)

A statistical failure theory for brittle materials that traces its origins to the Weibull distribution function is developed for use in the general purpose ABAQUS finite element computer program. One of the fundamental assumptions for this development is ...

J. Bennett

1991-01-01

93

EVALUATION OF SPRING OPERATED RELIEF VALVE MAINTENANCE INTERVALS AND EXTENSION OF MAINTENANCE TIMES USING A WEIBULL ANALYSIS WITH MODIFIED BAYESIAN UPDATING  

SciTech Connect

The Savannah River Site (SRS) spring operated pressure relief valve (SORV) maintenance intervals were evaluated using an approach provided by the American Petroleum Institute (API RP 581) for risk-based inspection technology (RBI). In addition, the impact of extending the inspection schedule was evaluated using Monte Carlo Simulation (MCS). The API RP 581 approach is characterized as a Weibull analysis with modified Bayesian updating provided by SRS SORV proof testing experience. Initial Weibull parameter estimates were updated as per SRS's historical proof test records contained in the Center for Chemical Process Safety (CCPS) Process Equipment Reliability Database (PERD). The API RP 581 methodology was used to estimate the SORV's probability of failing on demand (PFD), and the annual expected risk. The API RP 581 methodology indicates that the current SRS maintenance plan is conservative. Cost savings may be attained in certain mild service applications that present low PFD and overall risk. Current practices are reviewed and recommendations are made for extending inspection intervals. The paper gives an illustration of the inspection costs versus the associated risks by using API RP 581 Risk Based Inspection (RBI) Technology. A cost effective maintenance frequency balancing both financial risk and inspection cost is demonstrated.

Harris, S.; Gross, R.; Mitchell, E.

2011-01-18

94

An Application of Stochastic Programming with Weibull Distribution–Cluster Based Optimum Allocation of Recruitment in Manpower Planning  

Microsoft Academic Search

Recruitment of persons for various assignments with required talents in an organization is an important feature, since it plays a vital role in the growth of the organization. To achieve the required expertise in recruitment, in this paper Linear Stochastic Programming (LSP) is applied along with cluster analysis technique. The aim of this paper is to obtain an optimal allocation

M. Jeeva; Rajalakshmi Rajagopal; V. Charles; V. S. S. Yadavalli

2005-01-01

95

A Statistical Analysis of Wind Speed Distributions in the Area of Western Greece  

Microsoft Academic Search

The wind energy potential in Western Greece was evaluated from measurements of wind speed and direction at four weather stations. Data collected over a period of years were used to statistically analyze wind speed distributions. Weibull parameters, at the selected stations, were calculated using three different methods. The theoretical values calculated from the analysis of the collected data performed well

H. S. Bagiorgas; G. Mihalakakou; D. Matthopoulos

2008-01-01

96

Accurate Long-tailed Network Traffic Approximation and Its Queueing Analysis by Hyper-Erlang Distributions  

Microsoft Academic Search

Internet traffic has been proven to be long-tailed and often modeled by lognormal distribution, Weibull or Pareto distributions theoretically. However, these mathematical models hinder us in traffic analysis and evaluation studies due to their complex representations and theoretical properties. This paper proposes a hyper-Erlang model (mixed Erlang distribution) for such a long-tailed network traffic approximation. It fits network traffic with

Junfeng Wang; Hongxia Zhou; Lei Li; Fanjiang Xu

2005-01-01

97

Unsupervised Variational Image Segmentation\\/Classification Using a Weibull Observation Model  

Microsoft Academic Search

Studies have shown that the Weibull distribution can model accurately a wide variety of images. Its parameters index a family of distributions which includes the exponential and approximations of the Gaussian and the Raleigh models widely used in image segmentation. This study investigates the Weibull distribution in unsupervised image segmentation and classification by a variational method. The data term of

Ismail Ben Ayed; Nacera Hennane; Amar Mitiche

2006-01-01

98

Weibull-like Model of Cancer Development in Aging.  

PubMed

Mathematical modeling of cancer development is aimed at assessing the risk factors leading to cancer. Aging is a common risk factor for all adult cancers. The risk of getting cancer in aging is presented by a hazard function that can be estimated from the observed incidence rates collected in cancer registries. Recent analyses of the SEER database show that the cancer hazard function initially increases with the age, and then it turns over and falls at the end of the lifetime. Such behavior of the hazard function is poorly modeled by the exponential or compound exponential-linear functions mainly utilized for the modeling. In this work, for mathematical modeling of cancer hazards, we proposed to use the Weibull-like function, derived from the Armitage-Doll multistage concept of carcinogenesis and an assumption that number of clones at age t developed from mutated cells follows the Poisson distribution. This function is characterized by three parameters, two of which (r and ?) are the conventional parameters of the Weibull probability distribution function, and an additional parameter (C(0)) that adjusts the model to the observational data. Biological meanings of these parameters are: r-the number of stages in carcinogenesis, ?-an average number of clones developed from the mutated cells during the first year of carcinogenesis, and C(0)-a data adjustment parameter that characterizes a fraction of the age-specific population that will get this cancer in their lifetime. To test the validity of the proposed model, the nonlinear regression analysis was performed for the lung cancer (LC) data, collected in the SEER 9 database for white men and women during 1975-2004. Obtained results suggest that: (i) modeling can be improved by the use of another parameter A- the age at the beginning of carcinogenesis; and (ii) in white men and women, the processes of LC carcinogenesis vary by A and C(0), while the corresponding values of r and ? are nearly the same. Overall, the proposed Weibull-like model provides an excellent fit of the estimates of the LC hazard function in aging. It is expected that the Weibull-like model can be applicable to fit estimates of hazard functions of other adult cancers as well. PMID:20838610

Mdzinarishvili, Tengiz; Sherman, Simon

2010-08-24

99

Implications of nearshore processes on the significant wave height probability distribution  

Microsoft Academic Search

This paper analyzes the effect of hydrodynamic processes associated with the beach morphology on the long-term distribution of waves. This is made using the three parameter Weibull Probability Distribution Function for the significant wave height. The analysis shows the evolution of the Weibull position (A), scale (B) and shape (C) parameters at the three main scales of interest for engineering

Daniel González-Marco; Jose Maria Alsina; Agustin Sánchez-Arcilla

2008-01-01

100

Fracture strength of ultrananocrystalline diamond thin films-identification of Weibull parameters  

Microsoft Academic Search

The fracture strength of ultrananocrystalline diamond (UNCD) has been investigated using tensile testing of freestanding submicron films. Specifically, the fracture strength of UNCD membranes, grown by microwave plasma chemical vapor deposition (MPCVD), was measured using the membrane deflection experiment developed by Espinosa and co-workers. The data show that fracture strength follows a Weibull distribution. Furthermore, we show that the Weibull

H. D. Espinosa; B. Peng; B. C. Prorok; N. Moldovan; O. Auciello; J. A. Carlisle; D. M. Gruen; D. C. Mancini

2003-01-01

101

Sampling Inspection Plans for Discriminating Between Two Weibull Processes  

Microsoft Academic Search

Four procedures—R1, R2, R3 and R4, for choosing the better of two processes, the units from which have life times distributed according to the Weibull distribution were formulated in an earlier paper [1]. The calculation in the use of these procedures and some sampling plans based on them are discussed here. The paper also examines the robustness of these procedures.

A. S. Qureishi; K. J. Nabavian; J. D. Alanen

1965-01-01

102

Application of a stochastic, Weibull probability generator for replacing missing data on ambient concentrations of gaseous pollutants  

Microsoft Academic Search

A stochastic, three-parameter, Weibull frequency distribution, probability generator was tested by using theoretical data. Subsequently, it was applied to replace missing values of hourly atmospheric concentrations of trace gases that were continuously monitored at three study sites, for 2 years. The results were highly accurate and realistic. The cumulative means and the medians calculated by the Weibull method were intermediate

M. Nosal; A. H. Legge; S. V. Krupa

2000-01-01

103

Detection of known targets in Weibull clutter based on Neural Networks. Robustness study against target parameters changes  

Microsoft Academic Search

The coherent detection of targets in presence of clutter and noise is considered in this study. Several clutter models are proposed in the literature, although the commonly used for sea and land clutter returns is the Weibull one. Our case of study involves that the target is known a priori, the clutter is Weibull-distributed and a white Gaussian noise is

R. Vicen-Bueno; M. P. Jarabo-Amores; M. Rosa-Zurera; R. Gil-Pita; D. Mata-Moya

2008-01-01

104

Outage probability of selection combiner over exponentially correlated Weibull-gamma fading channels for arbitrary number of branches  

Microsoft Academic Search

Outage probability of a selection combiner (SC) receiver is analyzed over exponentially correlated composite Weibull-gamma fading channels. An expression for the joint probability density function (PDF) of multivariate, exponentially correlated Weibull-gamma distributed random variable is obtained. Using this joint PDF, we derive an expression for the outage probability of a SC receiver with arbitrary number of input branches. Obtained expressions

T. Reddy; R. Subadar; P. R. Sahu

2010-01-01

105

Shallow Flaws Under Biaxial Loading Conditions, Part II: Application of a Weibull Stress Analysis of the Cruciform Bend Specimen Using a Hydrostatic Stress Criterion  

SciTech Connect

Cruciform beam fracture mechanics specimensl have been developed in the Heavy Section Steel Technology (HSST) Program at Oak Ridge National Laboratory (ORNL) to introduce a prototypic, far- field, out-of-plane biaxird bending stress component in the test section that approximates the nonlinear biaxial stresses resulting from pressurized-thernxd-shock or pressure-temperature loading of a nuclear reactor pressure vessel (RPV). Matrices of cruciform beam tests were developed to investigate and quantify the effects of temperature, biaxial loading, and specimen size on fracture initiation toughness of two-dimensional (constant depth), shtdlow, surface flaws. Tests were conducted under biaxial load ratios ranging from uniaxial to equibiaxial. These tests demonstrated that biaxial loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for RPV materials. Two and three- parameter Weibull models have been calibrated using a new scheme (developed at the University of Illinois) that maps toughness data from test specimens with distinctly different levels of crack-tip constraint to a small scale yielding (SSY) Weibull stress space. These models, using the new hydrostatic stress criterion in place of the more commonly used maximum principal stress in the kernel of the OW integral definition, have been shown to correlate the experimentally observed biaxiaI effect in cruciform specimens, thereby providing a scaling mechanism between uniaxial and biaxial loading states.

Bass, B.R.; McAfee, W.J.; Williams, P.T.

1999-08-01

106

Atlas Distributed Analysis Tools  

NASA Astrophysics Data System (ADS)

The ATLAS production system has been successfully used to run production of simulation data at an unprecedented scale. Up to 10000 jobs were processed in one day. The experiences obtained operating the system on several grid flavours was essential to perform a user analysis using grid resources. First tests of the distributed analysis system were then performed. In the preparation phase data was registered in the LHC File Catalog (LFC) and replicated in external sites. For the main test, few resources were used. All these tests are only a first step towards the validation of the computing model. The ATLAS management computing board decided to integrate the collaboration efforts in distributed analysis in only one project, GANGA. The goal is to test the reconstruction and analysis software in a large scale Data production using Grid flavors in several sites. GANGA allows trivial switching between running test jobs on a local batch system and running large-scale analyses on the Grid; it provides job splitting and merging, and includes automated job monitoring and output retrieval.

de La Hoz, Santiago Gonzalez; Ruiz, Luis March; Liko, Dietrich

2008-06-01

107

A comparison of Weibull and. beta. sub Ic analyses of transition range data  

SciTech Connect

Specimen size effects on K{sub Jc} data scatter in the transition range of fracture toughness have been explained by external (weakest link) statistics. In this investigation, compact specimens of A 533 grade B steel were tested in sizes ranging from 1/2TC(T) to 4TC(T) with sufficient replication to obtain good three-parameter Weibull characterization of data distributions. The optimum fitting parameters for an assumed Weibull slope of 4 were calculated. External statistics analysis was applied to the 1/2TC(T) data to predict median K{sub Jc} values for 1TC(T), 2TC(T), and 4TC(T) specimens. The distributions from experimentally developed 1TC(T), 2TC(T), and 4TC(T) data tended to confirm the predictions. However, the extremal prediction model does not work well at lower-shelf toughness. At {minus}150{degree}C the extremal model predicts a specimen size effect where in reality there is no size effect.

McCabe, D.E.

1991-01-01

108

ATLAS reliability analysis  

SciTech Connect

Key elements of the 36 MJ ATLAS capacitor bank have been evaluated for individual probabilities of failure. These have been combined to estimate system reliability which is to be greater than 95% on each experimental shot. This analysis utilizes Weibull or Weibull-like distributions with increasing probability of failure with the number of shots. For transmission line insulation, a minimum thickness is obtained and for the railgaps, a method for obtaining a maintenance interval from forthcoming life tests is suggested.

Bartsch, R.R.

1995-09-01

109

A statistical analysis of wind speed data in west central part of Karnataka based on Weibull distribution function  

Microsoft Academic Search

Application of renewable energy sources in electric power systems is growing rapidly due to enhanced public concern for adverse environmental impacts and escalation in energy costs and shortage of fossil fuels associated with the use of conventional energy sources throughout the world. Environmental concerns and fuel cost uncertainties associated with the use these energy sources have resulted in rapid growth

B. G. Kumaraswamy; B. K. Keshavan; S. H. Jangamshetti

2009-01-01

110

Evaluation of a Probability Approach to Uncertainty in Benefit-Cost Analysis.  

National Technical Information Service (NTIS)

The research reported here tests the application of the Weibull probability distribution to the problem of uncertainty in benefit-cost analysis. While there is no formal theoretical basis for describing the stochastic behavior of variables in benefit-cost...

L. J. Mercer W. D. Morgan

1975-01-01

111

Distributions of personal VOC exposures: a population-based analysis.  

PubMed

Information regarding the distribution of volatile organic compound (VOC) concentrations and exposures is scarce, and there have been few, if any, studies using population-based samples from which representative estimates can be derived. This study characterizes distributions of personal exposures to ten different VOCs in the U.S. measured in the 1999--2000 National Health and Nutrition Examination Survey (NHANES). Personal VOC exposures were collected for 669 individuals over 2-3 days, and measurements were weighted to derive national-level statistics. Four common exposure sources were identified using factor analyses: gasoline vapor and vehicle exhaust, methyl tert-butyl ether (MBTE) as a gasoline additive, tap water disinfection products, and household cleaning products. Benzene, toluene, ethyl benzene, xylenes chloroform, and tetrachloroethene were fit to log-normal distributions with reasonably good agreement to observations. 1,4-Dichlorobenzene and trichloroethene were fit to Pareto distributions, and MTBE to Weibull distribution, but agreement was poor. However, distributions that attempt to match all of the VOC exposure data can lead to incorrect conclusions regarding the level and frequency of the higher exposures. Maximum Gumbel distributions gave generally good fits to extrema, however, they could not fully represent the highest exposures of the NHANES measurements. The analysis suggests that complete models for the distribution of VOC exposures require an approach that combines standard and extreme value distributions, and that carefully identifies outliers. This is the first study to provide national-level and representative statistics regarding the VOC exposures, and its results have important implications for risk assessment and probabilistic analyses. PMID:18378311

Jia, Chunrong; D'Souza, Jennifer; Batterman, Stuart

2008-04-01

112

A method of moments for the estimation of Weibull pdf parameters  

Microsoft Academic Search

In order to estimate the parameters of a Weibull distribution, we study the performance of the method of moments. For that reason, we compare tree methods for the estimation of the cumulative distribution. The first method is a classical commonly-used approximation, the second one is the \\

VINCENZO NIOLA; ROSARIO OLIVIERO; GIUSEPPE QUAREMBA

2006-01-01

113

Life-Test Sampling Plans for Two-Parameter Weibull Populations  

Microsoft Academic Search

In this paper, we give variables sampling plans for items whose failure times are distributed as either extreme-value variates or Weibull variates (the logarithms of which are from an extreme-value distribution). Tables applying to acceptance regions and operating characteristics for sample size n, ranging from 3 to 18, are given. The tables allow for Type II censoring, with censoring number

K. W. Fertig; Nancy R. Mann

1980-01-01

114

Methods for estimating wind speed frequency distributions  

Microsoft Academic Search

The Weibull function is discussed for representation of the wind speed frequency distribution. Methods are presented for estimating the two Weibull parameters (scale factor c and shape factor k) from simple wind statistics. Comparison is made with a recently proposed method based on the ''square-root-normal'' distribution with mean wind speed and fastest mile data as input statistics. The Weibull distribution

C. G. Justus; W. R. Hargraves; Amir Mikhail; Denise Graber

1978-01-01

115

Data Reduction with Grouping and Weibull Models.  

National Technical Information Service (NTIS)

The computational details are given for a two-step procedure for condensing size-graded data, especially bio-medical data, into a parametric statistical model. The first step establishes a histogram of size density while the second fits a Weibull model to...

R. C. Dubes

1970-01-01

116

Characterisation of Lint Particle Removal in Offset Printing with Weibull Statistics  

Microsoft Academic Search

Linting is the process where small particles are removed from the surface of newsprint during offset printing. The buildup of these particles on the offset printing blanket is one of the major quality issues in offset printing. In this study, we apply Weibull statistics to particle size distribution of lint collected after both sheet-fed, printing either 1500 or 3000 copies,

Warren Batchelor; Afriana Sudarno

2010-01-01

117

A Weibull brittle material failure model for the ABAQUS computer program  

Microsoft Academic Search

A statistical failure theory for brittle materials that traces its origins to the Weibull distribution function is developed for use in the general purpose ABAQUS finite element computer program. One of the fundamental assumptions for this development is that Mode 1 microfractures perpendicular to the direction of the principal stress contribute independently to the fast fracture. The theory is implemented

2010-01-01

118

The application of wavelet transform for estimating the shape parameter of a Weibull pdf  

Microsoft Academic Search

In this paper a method for the parameter estimation of a Weibull distribution is explained. It is based on the estimates of the cumulative probability function performed by a wavelet method. The estimates, obtained by the application of the proposed method, are compared with the results based on other literature estimators. In particular, it is shown that the estimates are

VINCENZO NIOLA; ROSARIO OLIVIERO; GIUSEPPE QUAREMBA

119

The reliability of Weibull estimators and their relation to defects in brittle materials  

Microsoft Academic Search

Considerable effort was undertaken in the literature to investigate the reliability of Weibull estimators for a precise description of the strength distribution of brittle materials. In this paper, an overview is given about the discussion on this research field. Different approaches using analytical or numerical methods are presented, which are used to estimate the statistical uncertainty of test results. It

D. LOIDL; H. PETERLIK

120

Censored Weibull statistics in the dielectric breakdown of thin oxide films  

Microsoft Academic Search

Self-healing dielectric breakdown in thin oxide films has been shown to obey Weibull statistics after allowance has been made for both left and right censoring that is intrinsic to the measuring technique. Two overlapping distributions have been found under constant DC voltage stress testing but under ramp stress conditions these were not always observed. Nevertheless it is shown that the

S. M. Rowland; R. M. Hill; L. A. Dissado

1986-01-01

121

Spatial and temporal patterns of global onshore wind speed distribution  

NASA Astrophysics Data System (ADS)

Wind power, a renewable energy source, can play an important role in electrical energy generation. Information regarding wind energy potential is important both for energy related modeling and for decision-making in the policy community. While wind speed datasets with high spatial and temporal resolution are often ultimately used for detailed planning, simpler assumptions are often used in analysis work. An accurate representation of the wind speed frequency distribution is needed in order to properly characterize wind energy potential. Using a power density method, this study estimated global variation in wind parameters as fitted to a Weibull density function using NCEP/climate forecast system reanalysis (CFSR) data over land areas. The Weibull distribution performs well in fitting the time series wind speed data at most locations according to R2, root mean square error, and power density error. The wind speed frequency distribution, as represented by the Weibull k parameter, exhibits a large amount of spatial variation, a regionally varying amount of seasonal variation, and relatively low decadal variation. We also analyzed the potential error in wind power estimation when a commonly assumed Rayleigh distribution (Weibull k = 2) is used. We find that the assumption of the same Weibull parameter across large regions can result in non-negligible errors. While large-scale wind speed data are often presented in the form of mean wind speeds, these results highlight the need to also provide information on the wind speed frequency distribution.

Zhou, Yuyu; Smith, Steven J.

2013-09-01

122

Modelling memory processes and Internet response times: Weibull or power-law?  

NASA Astrophysics Data System (ADS)

The Weibull distribution is proposed as a model for response times. Theoretical support is offered by classical results for extreme-value distributions. Fits of the Weibull distribution to response time data in different contexts show that this distribution (and the exponential distribution on small time-scales) perform better than the often-suggested power-law and logarithmic function. This study suggests that the power-law can be viewed as an approximation, at neural level, for the aggregate strength of superposed memory traces that have different decay rates in distinct parts of the brain. As we predict, this view does not find support at the level of induced response processes. The distinction between underlying and induced processes might also be considered in other fields, such as engineering, biology and physics.

Chessa, Antonio G.; Murre, Jaap M. J.

2006-07-01

123

DASH -- Distributed Analysis System Hierarchy  

NASA Astrophysics Data System (ADS)

DASH is a distributed data reduction and analysis system constructed on CORBA. It plays an important role in the SUBARU computer system not only as an offline analysis system but also as a test and development environment of online quick analysis. We abstracted an object from astronomical data reduction/analysis procedures; `PROCube' (data reduction PROcedure Cube) and implemented it, so that we could share and reuse the reduction procedure. We are also trying to make it possible to retrieve sufficient original data for an analysis semi-automatically in cooperation with SUBARU data archive system (STARS).

Yagi, Masafumi; Mizumoto, Yoshihiko; Nishihara, Eiji; Yoshida, Michitoshi; Asai, Ryo; Chikada, Yoshihiro; Kosugi, George; Takata, Tadafumi; Ogasawara, Ryusuke; Ishihara, Yasuhide; Yanaka, Hiroshi; Morita, Yasuhiro; Nakamoto, Hiroyuki

124

Survival extrapolation using the poly-Weibull model.  

PubMed

Recent studies of (cost-) effectiveness in cardiothoracic transplantation have required estimation of mean survival over the lifetime of the recipients. In order to calculate mean survival, the complete survivor curve is required but is often not fully observed, so that survival extrapolation is necessary. After transplantation, the hazard function is bathtub-shaped, reflecting latent competing risks which operate additively in overlapping time periods. The poly-Weibull distribution is a flexible parametric model that may be used to extrapolate survival and has a natural competing risks interpretation. In addition, treatment effects and subgroups can be modelled separately for each component of risk. We describe the model and develop inference procedures using freely available software. The methods are applied to two problems from cardiothoracic transplantation. PMID:21937472

Demiris, Nikolaos; Lunn, David; Sharples, Linda D

2011-11-21

125

Collective Weibull behavior of social atoms: Application of the rank-ordering statistics to historical extreme events  

NASA Astrophysics Data System (ADS)

Analogous to crustal earthquakes in natural fault systems, we here consider the dynasty collapses as extreme events in human society. Duration data of ancient Chinese and Egyptian dynasties provides a good chance of exploring the collective behavior of the so-called social atoms. By means of the rank-ordering statistics, we demonstrate that the duration data of those ancient dynasties could be described with good accuracy by the Weibull distribution. It is thus amazing that the distribution of time to failure of human society, i.e. the disorder of a historical dynasty, follows the widely accepted Weibull process as natural material fails.

Chen, Chien-Chih; Tseng, Chih-Yuan; Telesca, Luciano; Chi, Sung-Ching; Sun, Li-Chung

2012-02-01

126

Analysis of seasonal wind speed and wind power density distribution in Aimangala wind form at Chitradurga Karnataka using two parameter weibull distribution function  

Microsoft Academic Search

Modeling of wind speed variation is an essential requirement in the estimation of wind energy potential for a typical site. In this paper, the average wind from April 2007 to March 2008 in Aimangala at central dry zone part of Karnataka, India have been statistically analyzed to determine wind energy potential for electrical power generation by grouping the seasonal observations.

B. G. Kumaraswamy; B. K. Keshavan; Y. T. Ravikiran

2011-01-01

127

Fitting the empirical distribution of intertrade durations  

NASA Astrophysics Data System (ADS)

Based on the analysis of a tick-by-tick data set used in the previous work by one of the authors (DJIA stocks traded at NYSE in October 1999), in this paper, we reject the hypothesis that tails of the empirical intertrade distribution are described by a power law. We further argue that the Tsallis q-exponentials are a viable tool for fitting and describing the unconditional distribution of empirical intertrade durations and they compare well to the Weibull distribution.

Politi, Mauro; Scalas, Enrico

2008-03-01

128

Distribution-free discriminant analysis  

SciTech Connect

This report describes our experience in implementing a non-parametric (distribution-free) discriminant analysis module for use in a wide range of pattern recognition problems. Issues discussed include performance results on both real and simulated data sets, comparisons to other methods, and the computational environment. In some cases, this module performs better than other existing methods. Nearly all cases can benefit from the application of multiple methods.

Burr, T.; Doak, J.

1997-05-01

129

Statistical analysis of multilook polarimetric SAR data and terrain classification with adaptive distribution  

NASA Astrophysics Data System (ADS)

This paper deals with analysis of statistical properties of multi-look processed polarimetric SAR data. Based on an assumption that the multi-look polarimetric measurement is a product between a Gamma-distributed texture variable and a Wishart-distributed polarimetric speckle variable, it is shown that the multi-look polarimetric measurement from a nonhomogeneous region obeys a generalized K-distribution. In order to validate this statistical model, two of its varied versions, multi-look intensity and amplitude K-distributions are particularly compared with histograms of the observed multi-look SAR data of three terrain types, ocean, forest-like and city regions, and with four empirical distribution models, Gaussian, log-normal, gamma and Weibull models. A qualitative relation between the degree of nonhomogeneity of a textured scene and the well-fitting statistical model is then empirically established. Finally, a classifier with adaptive distributions guided by the order parameter of the texture distribution estimated with local statistics is introduced to perform terrain classification, experimental results with both multi-look fully polarimetric data and multi-look single-channel intensity/amplitude data indicate its effectiveness.

Liu, Guoqing; Huang, Shunji; Torre, Andrea; Rubertone, Franco S.

1995-11-01

130

On the q-type distributions  

NASA Astrophysics Data System (ADS)

Various q-type distributions have appeared in the physics literature in the recent years, see e.g. L.C. Malacarne, R.S. Mendes, E. K. Lenzi, q-exponential distribution in urban agglomeration, Phys. Rev. E 65, (2002) 017106. S.M.D. Queiros, On a possible dynamical scenario leading to a generalised Gamma distribution, in xxx.lanl.gov-physics/0411111. U.M.S. Costa, V.N. Freire, L.C. Malacarne, R.S. Mendes, S. Picoli Jr., E.A. de Vasconcelos, E.F. da Silva Jr., An improved description of the dielectric breakdown in oxides based on a generalized Weibull distribution, Physica A 361, (2006) 215. S. Picoli, Jr., R.S. Mendes, L.C. Malacarne, q-exponential, Weibull, and q-Weibull distributions: an empirical analysis, Physica A 324 (2003) 678 688. A.M.C. de Souza, C. Tsallis, Student's t- and r- distributions: unified derivation from an entropic variational principle, Physica A 236 (1997) 52 57. It is pointed out in the paper that many of these are the same as or particular cases of what has been known in the statistics literature. Several of these statistical distributions are discussed and references provided. We feel that this paper could be of assistance for modeling problems of the type considered by L.C. Malacarne, R.S. Mendes, E. K. Lenzi, q-exponential distribution in urban agglomeration, Phys. Rev. E 65, (2002) 017106. S.M.D. Queiros, On a possible dynamical scenario leading to a generalised Gamma distribution, in xxx.lanl.gov-physics/0411111. U.M.S. Costa, V.N. Freire, L.C. Malacarne, R.S. Mendes, S. Picoli Jr., E.A. de Vasconcelos, E.F. da Silva Jr., An improved description of the dielectric breakdown in oxides based on a generalized Weibull distribution, Physica A 361, (2006) 215. S. Picoli, Jr., R.S. Mendes, L.C. Malacarne, q-exponential, Weibull, and q-Weibull distributions: an empirical analysis, Physica A 324 (2003) 678 688. A.M.C. de Souza, C. Tsallis, Student's t- and r- distributions: unified derivation from an entropic variational principle, Physica A 236 (1997) 52 57 and others.

Nadarajah, Saralees; Kotz, Samuel

2007-04-01

131

Review: likelihood method for fitting Weibull log-linear models to accelerated life-test data  

Microsoft Academic Search

The analysis of data from accelerated life-test experiments via the method of maximum likelihood estimation must, for a Weibull log-linear model, be performed numerically. This paper promotes a particular log-likelihood as the basis for such inferences, and introduces notation and formulae to aid the implementation of various numerical methods. Two examples illustrate the performance of a widely-used maximization technique; these

Alan J. Watkins; Reader Aids

1994-01-01

132

Biological implications of the Weibull and Gompertz models of aging.  

PubMed

Gompertz and Weibull functions imply contrasting biological causes of demographic aging. The terms describing increasing mortality with age are multiplicative and additive, respectively, which could result from an increase in the vulnerability of individuals to extrinsic causes in the Gompertz model and the predominance of intrinsic causes at older ages in the Weibull model. Experiments that manipulate extrinsic mortality can distinguish these biological models. To facilitate analyses of experimental data, we defined a single index for the rate of aging (omega) for the Weibull and Gompertz functions. Each function described the increase in aging-related mortality in simulated ages at death reasonably well. However, in contrast to the Weibull omega(W), the Gompertz omega(G) was sensitive to variation in the initial mortality rate independently of aging-related mortality. Comparisons between wild and captive populations appear to support the intrinsic-causes model for birds, but give mixed support for both models in mammals. PMID:11818426

Ricklefs, Robert E; Scheuerlein, Alex

2002-02-01

133

Theory of radar detection in coherent Weibull clutter  

NASA Astrophysics Data System (ADS)

The problem of detecting radar targets embedded in coherent Weibull clutter is considered. A mathematical procedure is developed that makes it possible to obtain a coherent sequence having a Weibull pdf for the amplitude, a uniform pdf for the phase, and an autocorrelation function, between the successive samples, selected at will. The newly introduced 'coherent Weibull clutter' (CWC) represents a suitable generalization of the conventional 'coherent Gaussian clutter'. A new family of processing schemes is derived in accordance with the statistical model assumed for the useful target, considering the following cases: a target known a priori; Swerling 0, 1, and 2 models; a partially fluctuating target; and a target modeled as a coherent Weibull process.

Farina, A.; Russo, A.; Scannapieco, F.; Barbarossa, S.

1987-04-01

134

Reliability Analysis in Distributed Systems  

Microsoft Academic Search

Reliability of a distributed processing system is an important design parameter that can be described in terms of the reliability of processing elements and communication links and also of the redundancy of programs and data files. The traditional terminal-pair reliability does not capture the redundancy of programs and files in a distributed system. Two reliability measures are introduced: distributed program

Cauligi S. Raghavendra; Viktor K. Prasanna; Salim Hariri

1988-01-01

135

Strength Distribution in Paper.  

National Technical Information Service (NTIS)

Tensile strength distributions are studied in four papers samples that exhibit a variety of brittle-to-ductile properties. 1005 tensile specimens were measured in each case. The standard Gumbel and Weibull distributions, and a recently proposed double exp...

M. J. Korteoja L. I. Salminen K. J. Niskanen M. Alava

1997-01-01

136

Reliability analysis of distribution networks  

Microsoft Academic Search

Monitoring of failures and outages in the transmission and distribution of electrical energy is necessary for determination of the reliability of network components and the supply of electrical energy to consumers. Incorrect input data leads, of course, to false results even if the correct computing method is used. The paper deals with obtaining of reliability indices of distribution network analyzing

Radomir Gono; Stanislav Rusek; Michal Kratky

2007-01-01

137

Analysis of Segmented Spatial Distributions.  

National Technical Information Service (NTIS)

Together with my PhD student Young Kim, I have explored how to deduce from spatially distributed moving point sets information relevant to situation awareness. A technology assessment of techniques from computational geometry has been augmented with new c...

2003-01-01

138

Application of the Weibull extrapolation to 137Cs geochronology in Tokyo Bay and Ise Bay, Japan.  

PubMed

Considerable doubt surrounds the nature of processes by which 137Cs is deposited in marine sediments, leading to a situation where 137Cs geochronology cannot be always applied suitably. Based on extrapolation with Weibull distribution, the maximum concentration of 137Cs derived from asymptotic values for cumulative specific inventory was used to re-establish 137Cs geochronology, instead of original 137Cs profiles. Corresponding dating results for cores in Tokyo Bay and Ise Bay, Japan, by means of this new method, are in much closer agreement with those calculated from 210Pb method than the previous method. PMID:15023446

Lu, Xueqiang

2004-01-01

139

Distributed computing and nuclear reactor analysis  

SciTech Connect

Large-scale scientific and engineering calculations for nuclear reactor analysis can now be carried out effectively in a distributed computing environment, at costs far lower than for traditional mainframes. The distributed computing environment must include support for traditional system services, such as a queuing system for batch work, reliable filesystem backups, and parallel processing capabilities for large jobs. All ANL computer codes for reactor analysis have been adapted successfully to a distributed system based on workstations and X-terminals. Distributed parallel processing has been demonstrated to be effective for long-running Monte Carlo calculations.

Brown, F.B.; Derstine, K.L.; Blomquist, R.N.

1994-03-01

140

MLP-Based Detection of Targets in Clutter: Robustness with Respect to the Shape Parameter of Weibull-Disitributed Clutter  

Microsoft Academic Search

Obtaining analytical expressions for coherent detection of known signals in Weibul-distributed clutter and white Gaussian\\u000a noise has been a hard task since the last decades. In fact, nowadays, these expressions have not been found yet. This problem\\u000a lead us to use suboptimum solutions to solve this problem. Optimum approximations can be done by using Multilayer Perceptrons\\u000a (MLPs) trained in a

Raul Vicen-bueno; Eduardo Galán-fernández; Manuel Rosa-zurera; Maria P. Jarabo-amores

2008-01-01

141

The use of wind probability distributions derived from the maximum entropy principle in the analysis of wind energy. A case study  

Microsoft Academic Search

This paper analyses the use of a general probability distribution obtained through application of the maximum entropy principle (MEP), constrained by the low-order statistical moments of a given set of wind speed data, in the estimation of wind energy. For this purpose, a comparison is made between the two parameter Weibull distribution and the distributions obtained through the MEP. This

Penélope Ramírez; José Antonio Carta

2006-01-01

142

A static analysis method to determine the availability of kinetic energy from wind turbines  

Microsoft Academic Search

This paper introduces definitions and an analysis method for estimating how much kinetic energy can be made available for inertial response from a wind turbine over a year, and how much energy capture must be sacrificed to do so. The analysis is based on the static characteristics of wind turbines, Weibull distributions of wind speed, and standard definitions of turbulence

Barry G. Rawn; Madeleine Gibescu; Wil L. Kling

2010-01-01

143

Probabilistic Weibull behavior and mechanical properties of MEMS brittle materials  

Microsoft Academic Search

The objective of this work is to present a brief overview of a probabilistic design methodology for brittle structures, review the literature for evidence of probabilistic behavior in the mechanical properties of MEMS (especially strength), and to investigate whether evidence exists that a probabilistic Weibull effect exists at the structural microscale. Since many MEMS devices are fabricated from brittle materials,

O. M. Jadaan; N. N. Nemeth; J. Bagdahn; W. N. Sharpe

2003-01-01

144

Order Statistic and Algebraic Product CFAR Detector for Weibull Clutter  

Microsoft Academic Search

A new radar constant false alarm rate (CFAR) detection algorithm operating in Weibull clutter is developed. In the proposed CFAR detector, that called order statistic and algebraic product (OSAP) CFAR detector, the output of OS processors on the both lagging and leading windows around the test cell are weighted by fuzzy weighting function (membership function) and are combined by algebraic

A. Zaimbashi; M. R. Taban; M. M. Nayebi

2006-01-01

145

Random effects Weibull regression model for occupational lifetime  

Microsoft Academic Search

High job turnover rate can cause many problems and each company needs proper strategies to prevent the brain-drain of its manpower. For effective human resource management, predicting the occupational life expectancy or the mean residual life of those who are to leave and join another company is important. In this paper, we propose a random effects Weibull regression model for

So Young Sohn; In Sang Chang; Tae Hee Moon

2007-01-01

146

Weibull-distributed radar clutter reflected from sea ice  

Microsoft Academic Search

Sea-ice clutter was measured using an X-band radar which is located at the city of Mombetsu in Hokkaido. The pulse width of the radar was 80 ns. To sample at 40 ns and record digitally, an emitter-coupled logic (ECL) was used as a high-speed IC. The sampled data were first transferred to a 64-kbyte dynamic-memory board and then to a

Hiroshi Ogawa; Matsuo Sekine; Toshimitsu Musha; Masaaki Aota; Masayuki Ohi

1987-01-01

147

On the Impact of CFO for an MC-DS-CDMA System in Weibull Fading Environments  

Microsoft Academic Search

On the basis of CFO (carrier frequency offset) point of view, the system performance results from the analysis by adopting\\u000a the channel scenarios characterized as Weibull fading for an MC-DS-CDMA (multi-carrier direct-sequence coded-division multiple-access)\\u000a system is proposed in this article. Moreover, an approximate simple expression with the criterion of BER (bit error rate)\\u000a versus SNR (signal-to-noise ratio) method is derived

Joy Iong-Zong Chen; Wen Ching Kuo

148

Voltage Stability Analysis of Radial Distribution Networks  

Microsoft Academic Search

The paper presents voltage stability analysis of radial distribution networks. A new stability index is proposed to identify the nodes that are on the verge of voltage collapse. The value of the proposed voltage stability index is calculated at each node of the network. A modified load flow method is used for voltage stability analysis. The modified load flow method

R. RANJAN; D. DAS

2003-01-01

149

Real time distribution analysis for electric utilities  

Microsoft Academic Search

Electric utilities are finding it increasingly necessary to better monitor, analyze and control their distribution systems. Planning and operation of the grid is increasing in complexity on one hand but subject to ever more binding constraints on the other. Real-time analysis is being seen as necessary to achieve acceptable operational efficiencies and quality of service. Real-time analysis is the combination

Jim See; W. Carr; S. E. Collier

2008-01-01

150

Parametric survival analysis and taxonomy of hazard functions for the generalized gamma distribution.  

PubMed

The widely used Cox proportional hazards regression model for the analysis of censored survival data has limited utility when either hazard functions themselves are of primary interest, or when relative times instead of relative hazards are the relevant measures of association. Parametric regression models are an attractive option in situations such as this, although the choice of a particular model from the available families of distributions can be problematic. The generalized gamma (GG) distribution is an extensive family that contains nearly all of the most commonly used distributions, including the exponential, Weibull, log normal and gamma. More importantly, the GG family includes all four of the most common types of hazard function: monotonically increasing and decreasing, as well as bathtub and arc-shaped hazards. We present here a taxonomy of the hazard functions of the GG family, which includes various special distributions and allows depiction of effects of exposures on hazard functions. We applied the proposed taxonomy to study survival after a diagnosis of clinical AIDS during different eras of HIV therapy, where proportionality of hazard functions was clearly not fulfilled and flexibility in estimating hazards with very different shapes was needed. Comparisons of survival after AIDS in different eras of therapy are presented in terms of both relative times and relative hazards. Standard errors for these and other derived quantities are computed using the delta method and checked using the bootstrap. Description of standard statistical software (Stata, SAS and S-Plus) for the computations is included and available at http://statepi.jhsph.edu/software. PMID:17342754

Cox, Christopher; Chu, Haitao; Schneider, Michael F; Muñoz, Alvaro

2007-10-15

151

Weibull models of fracture strengths and fatigue behavior of dental resins in flexure and shear.  

PubMed

In estimating lifetimes of dental restorative materials, it is useful to have available data on the fatigue behavior of these materials. Current efforts at estimation include several untested assumptions related to the equivalence of flaw distributions sampled by shear, tensile, and compressive stresses. Environmental influences on material properties are not accounted for, and it is unclear if fatigue limits exist. In this study, the shear and flexural strengths of three resins used as matrices in dental restorative composite materials were characterized by Weibull parameters. It was found that shear strengths were lower than flexural strengths, liquid sorption had a profound effect on characteristic strengths, and the Weibull shape parameter obtained from shear data differed for some materials from that obtained in flexure. In shear and flexural fatigue, a power law relationship applied for up to 250,000 cycles; no fatigue limits were found, and the data thus imply only one flaw population is responsible for failure. Again, liquid sorption adversely affected strength levels in most materials (decreasing shear strengths and flexural strengths by factors of 2-3) and to a greater extent than did the degree of cure or material chemistry. PMID:9730059

Baran, G R; McCool, J I; Paul, D; Boberick, K; Wunder, S

1998-01-01

152

Towards Distributed Memory Parallel Program Analysis  

SciTech Connect

This paper presents a parallel attribute evaluation for distributed memory parallel computer architectures where previously only shared memory parallel support for this technique has been developed. Attribute evaluation is a part of how attribute grammars are used for program analysis within modern compilers. Within this work, we have extended ROSE, a open compiler infrastructure, with a distributed memory parallel attribute evaluation mechanism to support user defined global program analysis required for some forms of security analysis which can not be addressed by a file by file view of large scale applications. As a result, user defined security analyses may now run in parallel without the user having to specify the way data is communicated between processors. The automation of communication enables an extensible open-source parallel program analysis infrastructure.

Quinlan, D; Barany, G; Panas, T

2008-06-17

153

Calibration of Weibull stress parameters using fracture toughness data  

Microsoft Academic Search

The Weibull stress model for cleavage fracture of ferritic steels requires calibration of two micromechanics parameters \\u000a $$(m,\\\\sigma _u ) $$\\u000a . Notched tensile bars, often used for such calibrations at lower-shelf temperatures, do not fracture in the transition region\\u000a without extensive plasticity and prior ductile tearing. However, deep-notch bend and compact tension specimens tested in the\\u000a transition region can provide

X. Gao; C. Ruggieri; R. H. Dodds

1998-01-01

154

Weibull Effective Area for Hertzian Ring Crack Initiation Stress  

SciTech Connect

Spherical or Hertzian indentation is used to characterize and guide the development of engineered ceramics under consideration for diverse applications involving contact, wear, rolling fatigue, and impact. Ring crack initiation can be one important damage mechanism of Hertzian indentation. It is caused by sufficiently-high, surface-located, radial tensile stresses in an annular ring located adjacent to and outside of the Hertzian contact circle. While the maximum radial tensile stress is known to be dependent on the elastic properties of the sphere and target, the diameter of the sphere, the applied compressive force, and the coefficient of friction, the Weibull effective area too will be affected by those parameters. However, the estimations of a maximum radial tensile stress and Weibull effective area are difficult to obtain because the coefficient of friction during Hertzian indentation is complex, likely intractable, and not known a priori. Circumventing this, the Weibull effective area expressions are derived here for the two extremes that bracket all coefficients of friction; namely, (1) the classical, frictionless, Hertzian case where only complete slip occurs, and (2) the case where no slip occurs or where the coefficient of friction is infinite.

Jadaan, Osama M. [University of Wisconsin, Platteville; Wereszczak, Andrew A [ORNL; Johanns, Kurt E [ORNL

2011-01-01

155

Weibull modulus and fracture strength of highly porous hydroxyapatite.  

PubMed

Porous hydroxyapatite (HA) is used in a variety of applications including biomedical materials such as engineered bone materials and microbe filters. Despite the utility of the Weibull modulus, m, as a gauge of the mechanical reliability of brittle solids, there have been very few studies of m for porous HA. A recent study of porous HA that included the current authors (Fan, X., Case, E.D., Ren, F., Shu, Y., Baumann, M.J., 2012a. Journal of the Mechanical Behavior of Biomedical Materials. 8, 21-36) showed increases in m for porosity, P, approaching PG, the porosity of the green (unfired) specimen. In this paper, 18 groups of highly porous HA specimens (12 groups fabricated in this study and 6 groups from Fan et al., 2012a) were analyzed with P values from 0.59 to 0.62, where PG=0.62. The partially sintered HA specimens were fractured in biaxial flexure using a ring-on-ring test fixture. The fracture strength decreased monotonically with decreasing sintering temperature, Tsinter, from 4.8MPa for specimens sintered at 1025°C-0.66MPa for specimens sintered at 350°C. However, the Weibull modulus remained surprisingly high, ranging from 6.6 to 15.5. In comparison, for HA specimens with intermediate values of P, from about 0.1-0.55, the Weibull modulus tended to be lower (ranging from about 4 to 11) than the highly porous specimens included in this study. PMID:23478051

Fan, X; Case, E D; Gheorghita, I; Baumann, M J

2013-02-13

156

Fitting wind speed distributions: a case study  

Microsoft Academic Search

The wind speed data represented in the form of frequency curves show the shape of a potential model. The Weibull and Lognormal models are used for this purpose, with hourly mean wind speed data. This study deals with the estimation of the annual Weibull and Lognormal parameters from 20 locations in Navarre. The suitability of both distributions is judged from

A. Garcia; J. L. Torres; E. Prieto; A. de Francisco

1998-01-01

157

Analysis of Area Burned by Wildfires Through the Partitioning of a Probability Model1  

Microsoft Academic Search

An analysis of forest fires by using a partitioned probability distribution is presented. Area burned during afire is fitted to a probability model. This model is partitioned into small, medium, and large fires. Conditional expected values are computed for each partition. Two cases are presented: the two-parameter Weibull and the Truncated Shifted Pareto probability models. The methodology allows a comparison

Ernesto Alvarado; David V. Sandberg; Bruce B. Bare

158

Measurement of the particle spatial and velocity distributions in micro-abrasive jets  

Microsoft Academic Search

Novel experimental techniques for obtaining the particle spatial distribution and the velocity distribution across a micro-abrasive jet were presented and tested. The spatial distribution of particles within the jet was found by using a direct particle capture technique, and was found to depend on the nozzle diameter, following either a Weibull or a piecewise Weibull distribution. In general, the jet

T. Burzynski; M. Papini

2011-01-01

159

Note on the use of the inverse Gaussian distribution for wind energy applications  

SciTech Connect

The inverse Gaussian distribution is suggested as an alternative to the three-parameter Weibull distribution for the description of wind speed data with low frequencies of low speeds. A comparison of the two distributions indicates a region of strong similarity, corresponding reasonably well to three-parameter Weibull distributions which have been fitted to wind data.

Bardsley, W.E.

1980-09-01

160

On the Distribution of Earthquake Interevent Times and the Impact of Spatial Scale  

NASA Astrophysics Data System (ADS)

The distribution of earthquake interevent times is a subject that has attracted much attention in the statistical physics literature [1-3]. A recent paper proposes that the distribution of earthquake interevent times follows from the the interplay of the crustal strength distribution and the loading function (stress versus time) of the Earth's crust locally [4]. It was also shown that the Weibull distribution describes earthquake interevent times provided that the crustal strength also follows the Weibull distribution and that the loading function follows a power-law during the loading cycle. I will discuss the implications of this work and will present supporting evidence based on the analysis of data from seismic catalogs. I will also discuss the theoretical evidence in support of the Weibull distribution based on models of statistical physics [5]. Since other-than-Weibull interevent times distributions are not excluded in [4], I will illustrate the use of the Kolmogorov-Smirnov test in order to determine which probability distributions are not rejected by the data. Finally, we propose a modification of the Weibull distribution if the size of the system under investigation (i.e., the area over which the earthquake activity occurs) is finite with respect to a critical link size. keywords: hypothesis testing, modified Weibull, hazard rate, finite size References [1] Corral, A., 2004. Long-term clustering, scaling, and universality in the temporal occurrence of earthquakes, Phys. Rev. Lett., 9210) art. no. 108501. [2] Saichev, A., Sornette, D. 2007. Theory of earthquake recurrence times, J. Geophys. Res., Ser. B 112, B04313/1-26. [3] Touati, S., Naylor, M., Main, I.G., 2009. Origin and nonuniversality of the earthquake interevent time distribution Phys. Rev. Lett., 102 (16), art. no. 168501. [4] Hristopulos, D.T., 2003. Spartan Gibbs random field models for geostatistical applications, SIAM Jour. Sci. Comput., 24, 2125-2162. [5] I. Eliazar and J. Klafter, 2006. Growth-collapse and decay-surge evolutions, and geometric Langevin equations, Physica A, 367, 106 - 128.

Hristopulos, Dionissios

2013-04-01

161

Survival analysis and demographic parameters of the pupal parasitoid Coptera haywardi (Hymenoptera: Diapriidae), reared on Anastrepha fraterculus (Diptera: Tephritidae)  

Microsoft Academic Search

Coptera haywardi is an idiobiont pupal parasitoid of Tephritidae, and native to the Neotropical region. A survival analysis using a parametric survival fit approach was performed to generate survival curves and information relevant to mass rearing for augmentative biological control. Survival data for both male and female individuals were fitted to several distributions (Weibull, exponential, loglogistic, and lognormal), and the

Segundo R. Núñez-Campero; Sergio M. Ovruski; Martin Aluja

2012-01-01

162

Force distribution analysis of mechanochemically reactive dimethylcyclobutene.  

PubMed

Internal molecular forces can guide chemical reactions, yet are not straightforwardly accessible within a quantum mechanical description of the reacting molecules. Here, we present a force-matching force distribution analysis (FM-FDA) to analyze internal forces in molecules. We simulated the ring opening of trans-3,4-dimethylcyclobutene (tDCB) with on-the-fly semiempirical molecular dynamics. The self-consistent density functional tight binding (SCC-DFTB) method accurately described the force-dependent ring-opening kinetics of tDCB, showing quantitative agreement with both experimental and computational data at higher levels. Mechanical force was applied in two different ways, namely, externally by a constant pulling force and internally by embedding tDCB within a strained macrocycle-containing stiff stilbene. We analyzed the distribution of tDCB internal forces in the two different cases by FM-FDA and found that external force gave rise to a symmetric force distribution in the cyclobutene ring, which also scaled linearly with the external force, indicating that the force distribution was uniquely determined by the symmetric architecture of tDCB. In contrast, internal forces due to stiff stilbene resulted in an asymmetric force distribution within tDCB, which indicated a different geometry of force application and supported the important role of linkers in the mechanochemical reactivity of tDCB. In addition, three coordinates were identified through which the distributed forces contributed most to rate acceleration. These coordinates are mostly parallel to the coordinate connecting the two CH3 termini of tDCB. Our results confirm previous observations that the linker outside of the reactive moiety, such as a stretched polymer or a macrocycle, affects its mechanochemical reactivity. We expect FM-FDA to be of wide use to understand and quantitatively predict mechanochemical reactivity, including the challenging cases of systems within strained macrocycles. PMID:23843171

Li, Wenjin; Edwards, Scott A; Lu, Lanyuan; Kubar, Tomas; Patil, Sandeep P; Grubmüller, Helmut; Groenhof, Gerrit; Gräter, Frauke

2013-07-10

163

Probability Distributions  

NSDL National Science Digital Library

This page, created by Virginia Tech's Department of Statistics, provides users with a myriad of different applets presenting different probability distributions. Some of these include: binomial, Poisson, negative binomial, geometric, t, chi-squared, gamma, Weibull, log-normal, beta and f distributions. Each applet is presented with an explanation of its use and also an example. Featuring eleven different applets, this is a useful and plentiful resource.

Anderson-Cook, C.; Robinson, T.; Dorai-Raj, S.

2009-10-28

164

Shadow Imaging for Charge Distribution Analysis  

NASA Astrophysics Data System (ADS)

We briefly review the shadow imaging method for charge distribution analysis developed at Brookhaven. It is a unique electron-diffraction technique. Instead of focusing a small electron probe on the sample in conventional convergent beam electron diffraction, we focus the probe above (or below) the sample, resulting in parallel recording of dark-field images (shadow images), or PARODI. Because the method couples diffraction with imaging, it is thus suitable for studying crystals as well as their defects. We used this technique to accurately describe charge transfer that determines the functionality of technologically important materials. Examples are given for MgB2 superconductor and CaCu3Ti4O12 oxide that exhibits giant dielectric response. Discussions on non-spherical electron scattering factors and their parameterizations for direct observations of electron orbitals in atomic images are also included.

Zhu, Yimei; Wu, Lijun

165

Group reaction time distributions and an analysis of distribution statistics  

Microsoft Academic Search

Describes a method of obtaining an average reaction time (RT) distribution for a group of Ss. The method is particularly useful for cases in which data from many Ss are available but there are only 10–20 RT observations per S cell. Essentially, RTs for each S are organized in ascending order, and quantiles are calculated. The quantiles are then averaged

Roger Ratcliff

1979-01-01

166

Effects of dislocation density and sample-size on plastic yielding at the nanoscale: a Weibull-like framework.  

PubMed

Micro-compression tests have demonstrated that plastic yielding in nanoscale pillars is the result of the fine interplay between the sample-size (chiefly the diameter D) and the density of bulk dislocations ?. The power-law scaling typical of the nanoscale stems from a source-limited regime, which depends on both these sample parameters. Based on the experimental and theoretical results available in the literature, this paper offers a perspective about the joint effect of D and ? on the yield stress in any plastic regime, promoting also a schematic graphical map of it. In the sample-size dependent regime, such dependence is cast mathematically into a first order Weibull-type theory, where the power-law scaling the power exponent ? and the modulus m of an approximate (unimodal) Weibull distribution of source-strengths can be related by a simple inverse proportionality. As a corollary, the scaling exponent ? may not be a universal number, as speculated in the literature. In this context, the discussion opens the alternative possibility of more general (multimodal) source-strength distributions, which could produce more complex and realistic strengthening patterns than the single power-law usually assumed. The paper re-examines our own experimental data, as well as results of Bei et al. (2008) on Mo-alloy pillars, especially for the sake of emphasizing the significance of a sudden increase in sample response scatter as a warning signal of an incipient source-limited regime. PMID:21984409

Rinaldi, Antonio

2011-10-10

167

Offshore wind resource assessment with Standard Wind Analysis Tool (SWAT): A Rhode Island case study  

NASA Astrophysics Data System (ADS)

Motivated by the current Rhode Island Ocean SAMP (Special Area Management Plan) project and the growing need in the foreseeable future, analysis tools for wind resource assessment are assembled into a toolkit that can be accessed from a GIS. The analysis is demonstrated by application to the ongoing wind resource assessment of Rhode Island's offshore waters by the Ocean SAMP. The tool is called Standard Wind Analysis Tool (SWAT). SWAT utilizes a method for integrating observations from the study area or numerical model outputs to assemble the spatial distribution of the offshore wind resource. Available power is inferred from direct measurements of wind speed, but the shape of the atmospheric boundary layer or wind speed profile must be parameterized in order to extrapolate measurements to heights other than that of the measurements. The vertical wind speed profile is modeled with the basic power law assuming a 1/7 exponent parameter representing near-neutral or more accurately timeaverage conditions. As an alternate estimate from year long multi-level observations at a meteorological tower is employed. The basis for the power analysis is the 2- parameter Weibull probability distribution, recognized as standard in modeling typical wind speed distributions. A Monte-Carlo simulation of the Weibull probability density function provides the expected power densities at observation sites. Application to Rhode Island's coastal waters yields an estimated Weibull shape parameter of roughly 2 for the offshore environment and a Weibull scale parameter that increases with distance from the coast. Estimates of power in the SAMP study area range from 525 to 850 W/m² at an elevation of 80 meters based on an observed profile in the SAMP study area. Like the Weibull scale parameter, annual mean wind power increases with distance offshore.

Crosby, Alexander Robert

168

An Inframarginal Analysis Based Resource Allocation Method in Distributed Computing  

Microsoft Academic Search

The key of distributed computing is to fully utilize computing resources. However, the efficiency of distributed computing can always be affected by volatility of available nodes and uncertainty of network environment. In order to enhance resource allocation efficiency in distributed computing, this paper presents an inframarginal analysis based resource allocation method, which distributes computing task to the node with more

Liu Jun; Wang En Ze; Qiao Jian Zhong; Lin Shu Kuan

2010-01-01

169

Distributions of Nodal Prices in PJM Market  

NASA Astrophysics Data System (ADS)

As the deregulation of electric business proceeds, it is important to analyze the distributions of prices in the power market. In this paper, we analyze the nodal prices of the PJM market, which is representative of power markets in the US. First, we verify Weibull’s property of the distribution of nodal prices. Then we verify Poisson’s property of the interval of loss process.

Kunio, Matsumoto; Yoshio, Ichida; Michiko, Makino; Hiroaki, Tanaka

170

Parameter Estimation of the Mixed Generalized Gamma Distribution Using Maximum Likelihood Estimation and Minimum Distance Estimation.  

National Technical Information Service (NTIS)

The Generalized Gamma is an extremely flexible distribution that is useful for reliability modeling. Among its many special cases are the Weibull and Exponential distributions. A mixture of Generalized Gamma Distributions is even more useful because multi...

D. G. Boerrigter

1998-01-01

171

Holistic schedulability analysis for distributed hard real-time systems  

Microsoft Academic Search

This paper extends the current analysis associated with static priority pre-emptive based scheduling to address the wider problem of analysing schedulability of a distributed hard real-time system; in particular it derives analysis for a distributed system where tasks with arbitrary deadlines communicate by message passing and shared data areas. A simple TDMA protocol is assumed, and analysis developed to bound

Ken Tindell; John Clark

1994-01-01

172

Development and application of distribution network comprehensive analysis system  

Microsoft Academic Search

Through a system study of the fundamental theories of distribution network analysis, operation optimization and network architecture assessment, including static security analysis theory, power flow calculation method, state estimation technique, network optimization method, fault isolation and recovery algorithm, and reactive power optimization algorithm, etc, a graphic distribution network analysis system was developed. Feeder renovation and sectionalization is determined by using

Pengxiang Bi; Zhimai Li; Qing Jinl; Ruifeng Guo; Jimin Ma

2010-01-01

173

Expectation maximization-based likelihood inference for flexible cure rate models with Weibull lifetimes.  

PubMed

Recently, a flexible cure rate survival model has been developed by assuming the number of competing causes of the event of interest to follow the Conway-Maxwell-Poisson distribution. This model includes some of the well-known cure rate models discussed in the literature as special cases. Data obtained from cancer clinical trials are often right censored and expectation maximization algorithm can be used in this case to efficiently estimate the model parameters based on right censored data. In this paper, we consider the competing cause scenario and assuming the time-to-event to follow the Weibull distribution, we derive the necessary steps of the expectation maximization algorithm for estimating the parameters of different cure rate survival models. The standard errors of the maximum likelihood estimates are obtained by inverting the observed information matrix. The method of inference developed here is examined by means of an extensive Monte Carlo simulation study. Finally, we illustrate the proposed methodology with a real data on cancer recurrence. PMID:23740876

Balakrishnan, Narayanaswamy; Pal, Suvra

2013-06-01

174

Nonlinear Analyses for Embedded Cracks Under Pressurized Thermal Shock: Comparisons with FAVOR and Weibull Stress Approaches.  

National Technical Information Service (NTIS)

Thick-walled reactor pressure vessels (RPVs) can potentially experience rapid temperature and pressure changes under pressurized thermal shock (PTS) conditions. This work describes progress towards utilization of a Weibull stress approach for cleavage fra...

B. Wasiluk R. H. Dodds X. Qian

2008-01-01

175

Thermal fatigue reliability analysis for PBGA with Sn3.8Ag0.7Cu solder joints  

Microsoft Academic Search

In this work, thermal cycling reliability test and analysis for PBGA components with Sn-3.8Ag-0.7Cu solder joints were investigated. Based on test results, a two-parameter Weibull distribution model was used to determine the mean time to failure (MTTF) of PBGA components. The MTTF was used for validation of finite element analysis (FEA) results. FEA analysis using quarter model and submodeling method

F. X. Che; J. H. L. Pang

2004-01-01

176

Modified Weibull-derived spectrum for deep water significant wave height estimation  

Microsoft Academic Search

The modified Weibull spectrum is utilized to calculate the zeroth spectral moment (mo) using Monte Carlo integration methods. Then significant wave height (Hs) is calculated using the formula $$ {\\\\text{H}}_{\\\\text{s}} = 4\\\\sqrt {{\\\\text{m}}_{\\\\text{o}} } . $$ This is validated with observed buoy data and numerical wave model (WAM) predicted significant wave heights. The Weibull\\u000a parameters have been calculated using energy

G. Muraleedharan; Mourani Sinha; A. D. Rao; G. Latha; S. K. Dube

2009-01-01

177

Assessing the adequacy of Weibull survival models: a simulated envelope approach  

Microsoft Academic Search

The Weibull proportional hazards model is commonly used for analysing survival data. However, formal tests of model adequacy are still lacking. It is well known that residual-based goodness-of-fit measures are inappropriate for censored data. In this paper, a graphical diagnostic plot of Cox–Snell residuals with a simulated envelope added is proposed to assess the adequacy of Weibull survival models. Both

Yun Zhao; Andy H. Lee; Kelvin K. W. Yau; Geoffrey J. McLachlan

2011-01-01

178

Modeling and analysis of DC distribution systems  

Microsoft Academic Search

Research on modification and replacement of conventional AC distribution system to DC is widely undergoing. When DC distribution is applied in a system with DC-preferred appliances, it is possible to enhance energy consumption efficiency by reducing conversion losses. Moreover, renewable energy sources and storage devices can be fully utilized because they are more compatible with DC based system where generated

Gab-Su Seo; Jongbok Baek; Kyusik Choi; Hyunsu Bae; Bohyung Cho

2011-01-01

179

Approximating Distributions by Extended Generalized Lambda Distribution (XGLD)  

Microsoft Academic Search

The family of four-parameter generalized lambda distributions (GLD) is known for its high flexibility. It provides an approximation of most of the usual statistical distributions (e.g., normal, uniform, lognormal, Weibull, etc.). Although GLD is used in many fields where precise data modeling is required, there are some statistical distributions that could not be estimated with high precision. The main objective

M. Nili Ahmadabadi; Y. Farjami; M. B. Moghadam

2012-01-01

180

Analysis of thrips distribution: application of spatial statistics and ...  

Treesearch

Title: Analysis of thrips distribution: application of spatial statistics and Kriging ... analysis of such data assumes that the counts taken over space and time are ... Our on-line publications are scanned and captured using Adobe Acrobat. During  ...

181

Joint Distribution Process Analysis Center (JDPAC): Background and Current Capability.  

National Technical Information Service (NTIS)

The Joint Distribution Process Analysis Center serves as the analytical engine for USTRANSCOM and Component Commanders. Its mission is to provide analysis and engineering support to improve the nation's ability to move and sustain the Joint Force.

D. Van Veldhuizen

2007-01-01

182

Power Flow Analysis for Balanced and Unbalanced Radial Distribution Systems  

Microsoft Academic Search

This paper reports on an efficient method of power flow analysis for solving balanced and unbalanced radial distribution systems. The radial distribution system is modelled as a series of interconnected single feeders. Using Kirchoff's laws, a set of iterative power flow equations was developed to conduct the power flow studies. Due to the voltage dependency of loads in distribution systems,

H. M. Mok; S. Elangovan; M. M. A. Salama; Cao Longjian

183

Extreme value analysis of diamond-size distributions  

Microsoft Academic Search

Extreme value analysis provides a semiparametric method for analyzing the extreme long tails of skew distributions which may be observed when handling mining data. The estimation of important tail characteristics, such as the extreme value index, allows for a discrimination between competing distribution models. It measures the thickness of such long tailed distributions, if only a limited sample is available.

J. Caers; P. Vynckier; J. Beirlant; L. Rombouts

1996-01-01

184

Analysis of Distribution Research and Development Planning.  

National Technical Information Service (NTIS)

Three important areas of electric utility distribution system research have been identified: planning methods, system surveillance and control, and data file technology. This study developed information and factual data for use by EPRI in formulating rese...

L. Isaksen

1975-01-01

185

Software framework concepts for power distribution system analysis  

Microsoft Academic Search

Software design reuse has been discussed in the past at the component level through Design Patterns. A software framework is an approach to achieve software reusability for an entire domain. This paper presents architectural design concepts of a framework for power distribution system analysis. The commonalities of distribution system analysis, including components, topologies, and algorithms are considered. A layered architecture

Fangxing Li; Robert P. Broadwater

2004-01-01

186

A User-Oriented Power Distribution System Analysis Program.  

National Technical Information Service (NTIS)

This paper is a revision of a digital computer program written to perform a load flow and/or short circuit analysis of a power distribution system. The program has been named Power Distribution System Analysis Program (PDSAP). The program capacity is 250 ...

J. A. Underwood

1976-01-01

187

A User-Simplified Power Distribution System Analysis Program.  

National Technical Information Service (NTIS)

The paper addresses the problem of developing a user-simplified power distribution system analysis program. A computer program was written to perform a load-flow and/or short-circuit analysis of a power distribution system. The program utilizes sparsity p...

M. R. Heer

1975-01-01

188

Global QCD Analysis of Fragmentation and Parton Distribution Functions  

SciTech Connect

A new Quantum Chromodynamics (QCD) analysis framework of fragmentation and parton distribution functions has been developed by the TTAP (Team Towards global Analysis of the Proton and partons) collaboration. The Mellin transformation technique used in the analysis framework improved the computing speed, which allows us to perform further detailed analysis.

Miyachi, Yoshiyuki; Imazu, Yoshimitsu; Kobayashi, YuKi; Shibata, Toshi-Aki [Department of Physics, Tokyo Institute of Technology, O-okayama 2-12-1, Meguro, Tokyo, 152-8551 (Japan)

2009-08-04

189

DISTRIBUTION SYSTEM RELIABILITY ANALYSIS USING A MICROCOMPUTER  

EPA Science Inventory

Distribution system reliability for most utilities is maintained by the knowledge of a few key personnel. Generally, these water maintenance personnel use a good memory, repair records, a large wall map and a hydraulic model of the larger transmission mains to help identify probl...

190

Analysis of Sodalime Granule Size Distributions.  

National Technical Information Service (NTIS)

NEDU has developed a procedure for translating mesh sizes given in sodalime specifications to those sieve sizes used in testing laboratories. This procedure is used to establish model Gaussian and log-normal distributions that are capable of meeting the s...

J. R. Clarke

2002-01-01

191

Harmonic analysis of electrical distribution systems  

SciTech Connect

This report presents data pertaining to research on harmonics of electric power distribution systems. Harmonic data is presented on RMS and average measurements for determination of harmonics in buildings; fluorescent ballast; variable frequency drive; georator geosine harmonic data; uninterruptible power supply; delta-wye transformer; westinghouse suresine; liebert datawave; and active injection mode filter data.

NONE

1996-03-01

192

Probability Distribution Function of the Upper Equatorial Pacific Current Speeds.  

National Technical Information Service (NTIS)

The probability distribution function (PDF) of the upper (0-50 m) tropical Pacific current speeds (w), constructed from hourly ADCP data (1990- 2007) at six stations for the Tropical Atmosphere Ocean project, satisfies the two-parameter Weibull distributi...

P. C. Chu

2008-01-01

193

Derivation and Implementation of Exponential Functions to Model Axial Scattering Spectrometer Data Distributions.  

National Technical Information Service (NTIS)

This report details the mathematical derivation of the Weibull and gamma distribution functions for the purpose of approximating cloud droplet spectra data via a mathematical model, and analyzes the ability of each function to model the data distributions...

L. E. Belsky J. P. Lally P. L. Miller

1982-01-01

194

High resolution Wigner distribution using chirp Z-transform analysis  

Microsoft Academic Search

The chirp Z-transform is used in the Wigner distribution for high resolution spectrum analysis. It has the capability to zoom onto the area of the signal of interest, which makes it a very useful spectral analysis tool for analyzing nonstationary time-varying signals. This capability results in a more reliable and accurate spectral analysis on the time-frequency plane

Soo-Chang Pei; Ing-Ing Yang

1991-01-01

195

Analysis of the EM Field Distribution in Smart Home  

Microsoft Academic Search

The purpose of this paper is to analyze the EM field distribution in U-home which is a smart home of Kun Shan University. It is apparent that wireless devices in U-home become EM field emitters. This paper states the measurement and the analysis of the EM field distribution generated by those devices. The measurements focus on some popular frequency bands,

Churng-Jou Tsai; Bo-Yuan Tsai; Jinn-Kwei Guo; Chun-Lin Lu; Chang-Fan Liu; Yu-Sheng Lin; Yeong-Her Wang

2010-01-01

196

Traceable Content Distribution Using Wavelet Decomposition and Social Network Analysis  

Microsoft Academic Search

This paper identifies a novel secure content distribution framework based on wavelet decomposition and social network. The motivation is to facilitate trace illegally distributed content by using mapping between hierarchical community of social network and wavelet tree. Firstly, the host signal is encrypted, then the encrypted contents are delivered to users according to social network analysis, at last, the contents

Conghuan Ye; Ji Li; Zenggang Xiong

2012-01-01

197

Unified load flow analysis for emerging distribution systems  

Microsoft Academic Search

This paper proposes a unified load flow analysis for transmission and distribution systems, based on the fast decoupled power flow method (FDPF). The method is centered on an extension of the conventional per unit normalization to circumvent the problems caused by low X\\/R ratio faced by distribution systems. The proposed extension establishes a complex voltampere basis. A properly definition of

Elizete M. Lourenço; Tarcisio Loddi; Odilon L. Tortelli

2010-01-01

198

Distributed Problem Solving in Seismic Event Analysis: Final Report.  

National Technical Information Service (NTIS)

The accuracy of analyses for seismic events visible to more than one monitoring station can be improved by combining data from several stations and ''triangulating'' analyses. This sort of analysis is a natural candidate for distributed problem-solving ap...

L. Gasser

1987-01-01

199

WATER DISTRIBUTION SYSTEM ANALYSIS: FIELD STUDIES, MODELING AND MANAGEMENT  

EPA Science Inventory

The user?s guide entitled ?Water Distribution System Analysis: Field Studies, Modeling and Management? is a reference guide for water utilities and an extensive summarization of information designed to provide drinking water utility personnel (and related consultants and research...

200

Analysis of Temperature Distributions in TRUPACT II.  

National Technical Information Service (NTIS)

Based on a theoretical analysis, the steady-state temperature in a TRUPACT II loaded with 35.4 grams of Pu-238 (20 Watts, 612 Curies) may reach a maximum of 316/degree/F. This maximum temperature can be reduced to 137/degree/F if helium is used in the TRU...

A. D. Yu

1988-01-01

201

HammerCloud: A Stress Testing System for Distributed Analysis  

Microsoft Academic Search

Distributed analysis of LHC data is an I\\/O-intensive activity which places large demands on the internal network, storage, and local disks at remote computing facilities. Commissioning and maintaining a site to provide an efficient distributed analysis service is therefore a challenge which can be aided by tools to help evaluate a variety of infrastructure designs and configurations. HammerCloud (HC) is

Daniel C van der Ster; Johannes Elmsheuser; Mario Ubeda Garcia; Massimo Paladin

2011-01-01

202

Analysis of stress distribution in compression precracking  

Microsoft Academic Search

Purpose – The paper aims to shed some light on the effect of the notch\\/crack-tip stresses and their role on the cyclic plasticity and crack growth behavior in compression-compression fatigue. Design\\/methodology\\/approach – Compression precracking was studied using 2D finite element analysis for CT specimen. The final crack length and the shape of the crack front were compared with those obtained

Jianguo Yu; Daniel Kujawski

2010-01-01

203

Generalized Gumbel distribution  

Microsoft Academic Search

A generalization of the Gumbel distribution is presented to deal with general situations in modeling univariate data with broad range of skewness in the density function. This generalization is derived by considering a logarithmic transformation of an odd Weibull random variable. As a result, the generalized Gumbel distribution is not only useful for testing goodness-of-fit of Gumbel and reverse-Gumbel distributions

Kahadawala Cooray

2010-01-01

204

Analysis of Distribution Level Residential Demand Response  

SciTech Connect

Control of end use loads has existed in the form of direct load control for decades. Direct load control systems allow a utility to interrupt power to a medium to large size commercial or industrial customer a set number of times a year. With the current proliferation of computing resources and communications systems the ability to extend the direct load control systems now exists. Demand response systems now have the ability to not only engage commercial and industrial customers, but also the individual residential customers. Additionally, the ability exists to have automated control systems which operate on a continual basis instead of the traditional load control systems which could only be operated a set number of times a year. These emerging demand response systems have the capability to engage a larger portion of the end use load and do so in a more controlled manner. This paper will examine the impact that demand response systems have on the operation of an electric power distribution system.

Schneider, Kevin P.; Fuller, Jason C.; Chassin, David P.

2009-03-23

205

Application of Wigner distribution function for analysis of radio occultations  

Microsoft Academic Search

We present the Wigner distribution function (WDF) as an alternative to radio holographic (RH) analysis in the interpretation of radio occultation (RO) observations of the Earth's atmosphere. RH analysis is widely used in RO retrieval to isolate signal from noise and to identify atmospheric multipath. The same task is performed by WDF which also maps a 1-D wave function to

M. E. Gorbunov; K. B. Lauritsen; S. S. Leroy

2010-01-01

206

Neuronal model with distributed delay: analysis and simulation study for gamma distribution memory kernel  

Microsoft Academic Search

A single neuronal model incorporating distributed delay (memory)is proposed. The stochastic model has been formulated as a\\u000a Stochastic Integro-Differential Equation (SIDE) which results in the underlying process being non-Markovian. A detailed analysis\\u000a of the model when the distributed delay kernel has exponential form (weak delay) has been carried out. The selection of exponential\\u000a kernel has enabled the transformation of the

Karmeshu; Varun Gupta; K. V. Kadambari

2011-01-01

207

Spectral analysis and distributed lags in geographical studies of local unemployment: 2. Distributed lags  

Microsoft Academic Search

This is the second part of a two-part paper in which the related topics of spectral analysis and the identification and estimation of distributed-lag models between time series are discussed. This paper is mainly concerned with distributed-lag models, in particular the use of spectral estimators developed by Hannan. A number of previous studies have used the phase statistics from the

R Dunn

1983-01-01

208

Exact distribution of the peak streamflow  

Microsoft Academic Search

Iacobellis and Fiorentino (2000) and Fiorentino et al. (2006) proposed modeling the peak of direct streamflow as a product of two independent random variables: one gamma distributed and the other Weibull distributed. However, the papers did not provide any results on the theoretical probability distribution of the peak streamflow. In this note, we derive explicit expressions for the probability density

Saralees Nadarajah

2007-01-01

209

Determination of the End of Shelflife for Milk using Weibull Hazard Method  

Microsoft Academic Search

The shelf life of pasteurized milk is traditionally estimated by the counts of both total and psychrotrophic microbial load. This study examins the relationship between the total and psychrotophic microbial growth in milk and its sensory shelf life as measured using the Weibull hazard method. Milk was stored at five constant temperatures (2, 5, 7, 12 and 15 °C) and

W. S. Duyvesteyn; E. Shimoni; T. P. Labuza

2001-01-01

210

Optimization of sample number for Weibull function of brittle materials strength  

Microsoft Academic Search

The estimation of the parameters of the Weibull function was investigated with regard to reliability. The sample number, confident level, and relative error of estimated parameters are three key factors and should be involved for evaluating the strength of brittle materials. The results indicated that the scatter of scale parameter was much less than that of shape parameter. The relationship

Yongdong Xu; Laifei Cheng; Litong Zhang; Dantao Yan; Chang You

2001-01-01

211

Hyper-Efficient Estimator of the Location Parameter of the Weibull Laws.  

National Technical Information Service (NTIS)

In the paper the author obtained the hyper-efficient estimator of the location parameter of the Weibull laws when it is known a priori that their shape parameters fall within the semiclosed unit interval, (0,1). The existence of such a desirable estimator...

S. D. Dubey

1964-01-01

212

Influence of threshold parameters on cleavage fracture predictions using the Weibull stress model  

Microsoft Academic Search

This study explores applications of three-parameter Weibull stress models to predict cleavage fracture behavior in ferritic structural steels tested in the transition region. The work emphasizes the role of the threshold parameters (sth and sw - min) in cleavage fracture predictions of a surface crack specimen loaded predominantly in tension for an A515-70 pressure vessel steel. A recently proposed procedure

Claudio Ruggieri

2001-01-01

213

ANALYSIS OF DISTRIBUTION FEEDER LOSSES DUE TO ADDITION OF DISTRIBUTED PHOTOVOLTAIC GENERATORS  

SciTech Connect

Distributed generators (DG) are small scale power supplying sources owned by customers or utilities and scattered throughout the power system distribution network. Distributed generation can be both renewable and non-renewable. Addition of distributed generation is primarily to increase feeder capacity and to provide peak load reduction. However, this addition comes with several impacts on the distribution feeder. Several studies have shown that addition of DG leads to reduction of feeder loss. However, most of these studies have considered lumped load and distributed load models to analyze the effects on system losses, where the dynamic variation of load due to seasonal changes is ignored. It is very important for utilities to minimize the losses under all scenarios to decrease revenue losses, promote efficient asset utilization, and therefore, increase feeder capacity. This paper will investigate an IEEE 13-node feeder populated with photovoltaic generators on detailed residential houses with water heater, Heating Ventilation and Air conditioning (HVAC) units, lights, and other plug and convenience loads. An analysis of losses for different power system components, such as transformers, underground and overhead lines, and triplex lines, will be performed. The analysis will utilize different seasons and different solar penetration levels (15%, 30%).

Tuffner, Francis K.; Singh, Ruchi

2011-08-09

214

First Experiences with LHC Grid Computing and Distributed Analysis  

SciTech Connect

In this presentation the experiences of the LHC experiments using grid computing were presented with a focus on experience with distributed analysis. After many years of development, preparation, exercises, and validation the LHC (Large Hadron Collider) experiments are in operations. The computing infrastructure has been heavily utilized in the first 6 months of data collection. The general experience of exploiting the grid infrastructure for organized processing and preparation is described, as well as the successes employing the infrastructure for distributed analysis. At the end the expected evolution and future plans are outlined.

Fisk, Ian

2010-12-01

215

Entropy Methods For Univariate Distributions in Decision Analysis  

NASA Astrophysics Data System (ADS)

One of the most important steps in decision analysis practice is the elicitation of the decision-maker's belief about an uncertainty of interest in the form of a representative probability distribution. However, the probability elicitation process is a task that involves many cognitive and motivational biases. Alternatively, the decision-maker may provide other information about the distribution of interest, such as its moments, and the maximum entropy method can be used to obtain a full distribution subject to the given moment constraints. In practice however, decision makers cannot readily provide moments for the distribution, and are much more comfortable providing information about the fractiles of the distribution of interest or bounds on its cumulative probabilities. In this paper we present a graphical method to determine the maximum entropy distribution between upper and lower probability bounds and provide an interpretation for the shape of the maximum entropy distribution subject to fractile constraints, (FMED). We also discuss the problems with the FMED in that it is discontinuous and flat over each fractile interval. We present a heuristic approximation to a distribution if in addition to its fractiles, we also know it is continuous and work through full examples to illustrate the approach.

Abbas, Ali E.

2003-03-01

216

Analysis of stress distribution in the humeroradial joint.  

PubMed

Stress distribution in the humeroradial joint was analyzed with pressure-sensitive film, a tactile sensor, and by the three-dimensional finite element method. Fifteen cadaveric elbows with minimal osteoarthritic changes were loaded perpendicular to the articular surface of the radial head in the full pronation, supination, and neutral positions from 0 degrees to 90 degrees. Finite element analysis of stress distribution in the joint was based on a model of the same conditions. The patterns of stress distribution were similar with all three analysis methods. High stress was concentrated laterally in supination, and medially in the neutral and pronation positions. The results of the analyses closely resembled those found in some studies of the pathophysiology of degenerative changes in the humeroradial joint. PMID:12486468

Takatori, Kazuhiro; Hashizume, Hiroyuki; Wake, Hirofumi; Inoue, Hajime; Nagayama, Noriyuki

2002-01-01

217

Energy loss analysis of an integrated space power distribution system  

NASA Astrophysics Data System (ADS)

The results of studies related to conceptual topologies of an integrated utility-like space power system are described. The system topologies are comparatively analyzed by considering their transmission energy losses as functions of mainly distribution voltage level and load composition. The analysis is expedited by use of a Distribution System Analysis and Simulation (DSAS) software. This recently developed computer program by the Electric Power Research Institute (EPRI) uses improved load models to solve the power flow within the system. However, present shortcomings of the software with regard to space applications, and incompletely defined characteristics of a space power system make the results applicable to only the fundamental trends of energy losses of the topologies studied. Accountability, such as included, for the effects of the various parameters on the system performance can constitute part of a planning tool for a space power distribution system.

Kankam, M. D.; Ribeiro, P. F.

218

Ion energy distributions in rf sheaths; review, analysis and simulation  

Microsoft Academic Search

We present a review and analysis of ion energy distributions (IED) arriving at the target of a radio frequency (rf) discharge. We mainly discuss the collisionless regime, which is of great interest to experimentalists and modellers studying high-density discharges in which the sheath is much thinner than in conventional reactive ion etching systems. We assess what has been done so

E. Kawamura; V. Vahedi; M. A. Lieberman; C. K. Birdsall

1999-01-01

219

A Theory of Competitive Analysis for Distributed Algorithms  

Microsoft Academic Search

We introduce a theory of competitive analysis for distributed algorithms. The rst steps in this direction were made in the seminal papers of Bartal, Fiat, and Rabani (18), and of Awerbuch, Kutten, and Peleg (16), in the context of data management and job scheduling. In these papers, as well as in other subsequent work (4, 15, 19, 14), the cost

Miklos Ajtai; James Aspnes; Cynthia Dwork; Orli Waarts

220

Combining Probability Distributions From Experts in Risk Analysis  

Microsoft Academic Search

Abstract This paper concerns the combination of experts’ probability distributions in risk analysis, discussing a variety of combination methods,and attempting to highlight the important conceptual and practical issues to be considered in designing a combination process in practice. The role of experts is important because their judgments can provide valuable information, particularly in view of the limited availability of “hard

Robert T. Clemen; Robert L. Winkler

1999-01-01

221

Scenario-Driven Dynamic Analysis of Distributed Architectures  

Microsoft Academic Search

Software architecture constitutes a promising approach to the de- velopment of large-scale distributed systems, but architecture description languages (ADLs) and their associated architectural analysis techniques suf- fer from several important shortcomings. This paper presents a novel ap- proach that reconceptualizes ADLs within the model-driven engineering (MDE) paradigm to address their shortcomings. Our approach combines ex- tensible modeling languages based on

George Edwards; Sam Malek; Nenad Medvidovic

2007-01-01

222

Fréchet sensitivity analysis for partial differential equations with distributed parameters  

Microsoft Academic Search

This paper reviews Fr´ echet sensitivity analysis for partial differential equations with variations in distributed parameters. The Fr´ echet derivative provides a linear map be- tween parametric variations and the linearized response of the solution. We propose a methodology based on representations of the Frderivative operator to find those variations that lead to the largest changes to the solution (the

Jeff Borggaard; Vitor Leite Nunes

2011-01-01

223

Pointers and linked lists in electric power distribution circuit analysis  

Microsoft Academic Search

Electric power distribution circuit analysis programs must efficiently manage a large quantity of system and equipment data. Utility engineers now wish to use integrated software packages with several functions that work efficiently and share data. The use of data structures stored in linked lists and processed through pointers is described. The pointers and linked lists compact the data storage and

R. P. Broadwater; J. C. Thompson; T. E. McDermott

1991-01-01

224

Integrating software architectures for distributed simulations and simulation analysis communities.  

SciTech Connect

The one-year Software Architecture LDRD (No.79819) was a cross-site effort between Sandia California and Sandia New Mexico. The purpose of this research was to further develop and demonstrate integrating software architecture frameworks for distributed simulation and distributed collaboration in the homeland security domain. The integrated frameworks were initially developed through the Weapons of Mass Destruction Decision Analysis Center (WMD-DAC), sited at SNL/CA, and the National Infrastructure Simulation & Analysis Center (NISAC), sited at SNL/NM. The primary deliverable was a demonstration of both a federation of distributed simulations and a federation of distributed collaborative simulation analysis communities in the context of the same integrated scenario, which was the release of smallpox in San Diego, California. To our knowledge this was the first time such a combination of federations under a single scenario has ever been demonstrated. A secondary deliverable was the creation of the standalone GroupMeld{trademark} collaboration client, which uses the GroupMeld{trademark} synchronous collaboration framework. In addition, a small pilot experiment that used both integrating frameworks allowed a greater range of crisis management options to be performed and evaluated than would have been possible without the use of the frameworks.

Goldsby, Michael E.; Fellig, Daniel; Linebarger, John Michael; Moore, Patrick Curtis; Sa, Timothy J.; Hawley, Marilyn F.

2005-10-01

225

A new continuous distribution method for probabilistic load flow analysis  

SciTech Connect

The probabilistic load flow (PLF) analysis problem can be classified into the following two categories: linearization of the load flow equations of non-linear power system and convolution of the linearized input radon variables. Once the load flow equations are linearized, it becomes easier to perform the convolution with either numerical or analytical methods. In PLF, distributions of generation systems and loads are continuous, discrete, or mixture of these. There are a number of techniques for the convolution of these distributions, but most are based on direct manipulation of the convolution integral. Alternative methods have also been presented in the literature. In this paper, a new probability distribution for performing the convolution is proposed. The distribution is a composite of gamma distributions. This proposed generalized multiparameter distribution method is used for the convolution of linear combination of the input random variables. The cumulants of linear combination of random variables are obtained by adding the individual cumulants with weighting factors which are sometimes termed the sensitivity coefficients and are obtained from the given network data.

Kim, J.O.; Singh, C. (Texas A and M Univ., College Station, TX (United States). Dept. of Electrical Engineering)

1992-01-01

226

Influence Of Lateral Load Distributions On Pushover Analysis Effectiveness  

SciTech Connect

The effectiveness of two simple load distributions for pushover analysis recently proposed by the authors is investigated through a comparative study, involving static and dynamic analyses of seismic response of eccentrically braced frames. It is shown that in the upper floors only multimodal pushover procedures provide results close to the dynamic profile, while the proposed load patterns are always conservative in the lower floors. They over-estimate the seismic response less than the uniform distribution, representing a reliable alternative to the uniform or more sophisticated adaptive procedures proposed by seismic codes.

Colajanni, P.; Potenzone, B. [Dipartimento di Ingegneria Civile, Universita di Messina, Contrada Di Dio, S. Agata, 98166 Messina (Italy)

2008-07-08

227

Analysis of momentum distributions of projectile fragmentation products  

NASA Astrophysics Data System (ADS)

A model describing fragment momentum distributions as a function of the projectile energy has been developed. This model called “Universal parameterization” is based on the convolution between a gaussian distribution corresponding to Goldhaber model of fragmentation and an exponential attenuation arising from friction between projectile spectator and participant. An analysis of several experimental data sets has been performed to obtain the coefficients of the Universal Parameterization in order to avoid drawbacks inherent to the fragmentation statistical model. The Universal parameterization is incorporated in the LISE++ code for fragment transmission calculations.

Tarasov, O.

2004-04-01

228

Influence Of Lateral Load Distributions On Pushover Analysis Effectiveness  

NASA Astrophysics Data System (ADS)

The effectiveness of two simple load distributions for pushover analysis recently proposed by the authors is investigated through a comparative study, involving static and dynamic analyses of seismic response of eccentrically braced frames. It is shown that in the upper floors only multimodal pushover procedures provide results close to the dynamic profile, while the proposed load patterns are always conservative in the lower floors. They over-estimate the seismic response less than the uniform distribution, representing a reliable alternative to the uniform or more sophisticated adaptive procedures proposed by seismic codes.

Colajanni, P.; Potenzone, B.

2008-07-01

229

Spatial Distribution Analysis of Scrub Typhus in Korea  

PubMed Central

Objective: This study analyzes the spatial distribution of scrub typhus in Korea. Methods: A spatial distribution of Orientia tsutsugamushi occurrence using a geographic information system (GIS) is presented, and analyzed by means of spatial clustering and correlations. Results: The provinces of Gangwon-do and Gyeongsangbuk-do show a low incidence throughout the year. Some districts have almost identical environmental conditions of scrub typhus incidence. The land use change of districts does not directly affect the incidence rate. Conclusion: GIS analysis shows the spatial characteristics of scrub typhus. This research can be used to construct a spatial-temporal model to understand the epidemic tsutsugamushi.

Jin, Hong Sung; Chu, Chaeshin; Han, Dong Yeob

2013-01-01

230

Vibrational Energy Distribution Analysis (VEDA): Scopes and limitations  

NASA Astrophysics Data System (ADS)

The principle of operations of the VEDA program written by the author for Potential Energy Distribution (PED) analysis of theoretical vibrational spectra is described. Nowadays, the PED analysis is indispensible tool in serious analysis of the vibrational spectra. To perform the PED analysis it is necessary to define 3N-6 linearly independent local mode coordinates. Already for 20-atomic molecules it is a difficult task. The VEDA program reads the input data automatically from the Gaussian program output files. Then, VEDA automatically proposes an introductory set of local mode coordinates. Next, the more adequate coordinates are proposed by the program and optimized to obtain maximal elements of each column (internal coordinate) of the PED matrix (the EPM parameter). The possibility for an automatic optimization of PED contributions is a unique feature of the VEDA program absent in any other programs performing PED analysis.

Jamróz, Micha? H.

2013-10-01

231

Modelling Framework and the Quantitative Analysis of Distributed Energy Resources in Future Distribution Networks  

NASA Astrophysics Data System (ADS)

There has been a large body of statements claiming that the large-scale deployment of Distributed Energy Resources (DERs) could eventually reshape the future distribution grid operation in numerous ways. Thus, it is necessary to introduce a framework to measure to what extent the power system operation will be changed by various parameters of DERs. This article proposed a modelling framework for an overview analysis on the correlation between DERs. Furthermore, to validate the framework, the authors described the reference models of different categories of DERs with their unique characteristics, comprising distributed generation, active demand and electric vehicles. Subsequently, quantitative analysis was made on the basis of the current and envisioned DER deployment scenarios proposed for Sweden. Simulations are performed in two typical distribution network models for four seasons. The simulation results show that in general the DER deployment brings in the possibilities to reduce the power losses and voltage drops by compensating power from the local generation and optimizing the local load profiles.

Han, Xue; Sandels, Claes; Zhu, Kun; Nordström, Lars

2013-08-01

232

Maximum-Likelihood Estimation of the Parameters of gamma and Weibull Populations from Complete and from Censored Samples.  

National Technical Information Service (NTIS)

Iterative procedures are given for joint maximum-likelihood estimation, from complete and censored samples, of the three parameters of Gamma and of Weibull populations. For each of these populations, the likelihood function is written down, and the three ...

H. L. Harter A. H. Moore

1965-01-01

233

HammerCloud: A Stress Testing System for Distributed Analysis  

NASA Astrophysics Data System (ADS)

Distributed analysis of LHC data is an I/O-intensive activity which places large demands on the internal network, storage, and local disks at remote computing facilities. Commissioning and maintaining a site to provide an efficient distributed analysis service is therefore a challenge which can be aided by tools to help evaluate a variety of infrastructure designs and configurations. HammerCloud is one such tool; it is a stress testing service which is used by central operations teams, regional coordinators, and local site admins to (a) submit arbitrary number of analysis jobs to a number of sites, (b) maintain at a steady-state a predefined number of jobs running at the sites under test, (c) produce web-based reports summarizing the efficiency and performance of the sites under test, and (d) present a web-interface for historical test results to both evaluate progress and compare sites. HammerCloud was built around the distributed analysis framework Ganga, exploiting its API for grid job management. HammerCloud has been employed by the ATLAS experiment for continuous testing of many sites worldwide, and also during large scale computing challenges such as STEP'09 and UAT'09, where the scale of the tests exceeded 10,000 concurrently running and 1,000,000 total jobs over multi-day periods. In addition, HammerCloud is being adopted by the CMS experiment; the plugin structure of HammerCloud allows the execution of CMS jobs using their official tool (CRAB).

van der Ster, Daniel C.; Elmsheuser, Johannes; Úbeda García, Mario; Paladin, Massimo

2011-12-01

234

The truncated mean of an asymmetric distribution  

Microsoft Academic Search

This paper investigates a simple procedure to estimate robustly the mean of an asymmetric distribution. The procedure removes the observations which are larger or smaller than certain limits and takes the arithmetic mean of the remaining observations, the limits being determined with the help of a parametric model, e.g., the Gamma, the Weibull or the Lognormal distribution. The breakdown point,

A. Marazzi; C. Ruffieux

1999-01-01

235

Inferential Procedures for the Generalized Gamma Distribution.  

National Technical Information Service (NTIS)

The maximum likelihood estimators of the parameters of the generalized gamma distribution are shown to have the property that k', (b'/b) and (a'/a) sup b are distributed independently of a and b. Similar properties are also obtained for some Weibull-type ...

H. W. Hager L. J. Bain

1970-01-01

236

Statistical Length Scale in Weibull Strength Theory and Its Interaction with Other Scaling Lengths in Quasibrittle Failure  

Microsoft Academic Search

The main result of the paper is the introduction of a statistical length scale into the Weibull theory. The classical Weibull\\u000a strength theory is self-similar; a feature that can be illustrated by the fact that the strength dependence on structural\\u000a size is a power law (a straight line in double logarithmic plot). Therefore, the theory predicts unlimited strength for extremely

Miroslav Vo?echovský; Eligiusz Postek

237

Constraint effects on the ductile-to-brittle transition temperature of ferritic steels: a Weibull stress model  

Microsoft Academic Search

This study examines crack front length and constraint loss effects on cleavage fracture toughness in ferritic steels at temperatures in the ductile-to-brittle transition region. A local approach for fracture at the micro-scale of the material based on the Weibull stress is coupled with very detailed three-dimensional models of deep-notch bend specimens. A new non-dimensional function g(M) derived from the Weibull

X. Gao

2000-01-01

238

Coupling of the Weibull stress model and macroscale models to predict cleavage fracture  

Microsoft Academic Search

This study couples the ASTM E1921 procedure to characterize the ductile-to-brittle toughness of ferritic steels in terms of KJc (or Jc) values with the Weibull stress model, i.e., the “local approach” for fracture at the microscale. The E1921 procedures assume that uniform, small-scale yielding (SSY) conditions exist at fracture along the full crack-front, which supports the use of a simple

Jason P. Petti; Robert H. Dodds

2004-01-01

239

The generalized F distribution: an umbrella for parametric survival analysis.  

PubMed

In a recent tutorial my colleagues and I advocated the generalized gamma (GG) distribution as a platform for parametric survival analysis. The GG family includes all four of the common types of hazard functions, making it particularly useful for estimating individual hazard functions as well as both relative hazards and relative times. In addition, the GG includes most of the commonly used parametric survival distributions. Survival analysis based on the GG distribution is practical since regression models are available in commonly used statistical packages. It is well known that the GG is contained in an even larger family, the generalized F (GF) distribution, which also includes the log logistic. The GF thus provides additional flexibility for parametric modeling. In this paper we discuss the GF family from this perspective. We provide a characterization of the hazard functions of the GF, showing that, except for the GG, the available hazard functions are limited to decreasing and arc-shaped hazards and, in particular, that the hazard function can be decreasing but not monotone. We also discuss fitting the GF with an alternative parameterization using standard statistical software and refine a description of the hazard functions for death after a diagnosis of clinical AIDS in four different eras of HIV therapy. PMID:18407568

Cox, Christopher

2008-09-20

240

Distributed computing finite element electromagnetic analysis of traveling wave tubes  

Microsoft Academic Search

Purpose – The paper's aim is to focus on the utilization of the GRID distributed computing environment in order to reduce simulation time for parameter studies of travelling wave tube (TWT) electron guns and helix slow-wave structures. Design\\/methodology\\/approach – Two TWT finite-element analysis modules were adapted to be run on the GRID, for this purpose scripts were written to submit

Salvatore Coco; Antonino Laudani; Giuseppe Pollicino

2008-01-01

241

An Autoregressive Distributed Lag Modelling Approach to Cointegration Analysis  

Microsoft Academic Search

This paper examines the use of autoregressive distributed lag (ARDL) mod- els for the analysis of long-run relations when the underlying variables are I(1). It shows that after appropriate augmentation of the order of the ARDL model, the OLS estimators of the short-run parameters are p T-consistent with the as- ymptotically singular covariance matrix, and the ARDL-based estimators of the

M. Hashem Pesaran; Yongcheol Shin

1995-01-01

242

Dynamical analysis of Cohen Grossberg neural networks with distributed delays  

NASA Astrophysics Data System (ADS)

In this Letter, a model describing dynamics of Cohen Grossberg neural networks with distributed delays is considered. Without assuming Lipschitz conditions on activation functions, by employing Brouwer's fixed point theorem and applying inequality technique, some new sufficient conditions on the existence, uniqueness and exponential stability of equilibrium point are obtained. Finally, two examples with their numerical simulations are provided to show the correctness of our analysis.

Mao, Zisen; Zhao, Hongyong

2007-04-01

243

A digital computer program for radial distribution system analysis  

Microsoft Academic Search

A PC-based computer program for accurate analysis of radial distribution systems is described. Objected-oriented design philosophies are used, and the program takes advantage of data encapsulation and class separation to greatly simplify the software development and upgrading process. The program is a Microsoft Windows 3.1 application, and offers many special features to help the user make sound engineering decisions. The

James D. Foster; Robert A. Krieger; D. G. Flinn

1993-01-01

244

An Evaluation of Exponential and Weibull Test Plans  

Microsoft Academic Search

MIL-STD-781B gives sampling plans (sequential and fixed length) for reliability tests under the assumption of a constant failure rate. Using Monte Carlo techniques, the authors compare s-expected time to a decision and producer and consumer risks for some of these plans. It is shown that plans which assume an exponential distribution are not robust to departures from that assumption. A

H. Leon Harter; Albert H. Moore

1976-01-01

245

A description of the failure distributions of selected Minuteman 3 guidance system electronic cards  

NASA Astrophysics Data System (ADS)

This research described the failure distributions of selected Minuteman 3 guidance electronic cards and was the first attempt to use the Total Time on Test graphical technique to detect failure patterns. The data analysis was performed by using a Zenith 100 computer program that performed the Total Time on Test calculations and the Reliability Data Acquisition and Analysis Techniques software package. The objective of the research were to: (1) describe the failure distributions of selected Minuteman 3 electronic cards, (2) determine if the corresponding hazard function demonstrated infant mortality, useful life, or wearout, and (3) suggest management strategies to deal with wearout or infant mortality. Five individual cards were selected and the first three lifetimes of each card were examined. Nine of the fifteen cards indicated an exponential failure distribution, the other six were identified as either a Weibull or a normal failure distribution.

Sisk, Albert E.

1986-09-01

246

Growing axons analysis by using Granulometric Size Distribution  

NASA Astrophysics Data System (ADS)

Neurite growth (neuritogenesis) in vitro is a common methodology in the field of developmental neurobiology. Morphological analyses of growing neurites are usually difficult because their thinness and low contrast usually prevent to observe clearly their shape, number, length and spatial orientation. This paper presents the use of the granulometric size distribution in order to automatically obtain information about the shape, size and spatial orientation of growing axons in tissue cultures. The results here presented show that the granulometric size distribution results in a very useful morphological tool since it allows the automatic detection of growing axons and the precise characterization of a relevant parameter indicative of the axonal growth spatial orientation such as the quantification of the angle of deviation of the growing direction. The developed algorithms automatically quantify this orientation by facilitating the analysis of these images, which is important given the large number of images that need to be processed for this type of study.

Gonzalez, Mariela A.; Ballarin, Virginia L.; Rapacioli, Melina; Celín, A. R.; Sánchez, V.; Flores, V.

2011-09-01

247

Current Distribution Analysis of Insulated Gate Bipolar Transistor Cells  

NASA Astrophysics Data System (ADS)

In current insulated gate bipolar transistor (IGBT) technology, a corner or centered gate pad is employed with polycrystalline silicon (poly-Si) to form the metal oxide semiconductor (MOS) gate structure which forms a resistor-capacitor (RC) network across the die. This paper presents, for the first time, an analysis using circuit simulator, SABER, to analyze its influence on the internal behavior of the IGBT. The difference in the interconnect gate impedance between each cathode cells is found to influence their gate drive voltages, which results in the divergence of collector current within each cathode cells during transient periods. Proper distribution of the poly-Si gate impedance is necessary to achieve uniformity of current distribution in the device.

Hongyao Long,; Mark R. Sweet,; Luther-King Ngwendson,; E. M. Sankara Narayanan,

2010-04-01

248

Time series power flow analysis for distribution connected PV generation.  

SciTech Connect

Distributed photovoltaic (PV) projects must go through an interconnection study process before connecting to the distribution grid. These studies are intended to identify the likely impacts and mitigation alternatives. In the majority of the cases, system impacts can be ruled out or mitigation can be identified without an involved study, through a screening process or a simple supplemental review study. For some proposed projects, expensive and time-consuming interconnection studies are required. The challenges to performing the studies are twofold. First, every study scenario is potentially unique, as the studies are often highly specific to the amount of PV generation capacity that varies greatly from feeder to feeder and is often unevenly distributed along the same feeder. This can cause location-specific impacts and mitigations. The second challenge is the inherent variability in PV power output which can interact with feeder operation in complex ways, by affecting the operation of voltage regulation and protection devices. The typical simulation tools and methods in use today for distribution system planning are often not adequate to accurately assess these potential impacts. This report demonstrates how quasi-static time series (QSTS) simulation and high time-resolution data can be used to assess the potential impacts in a more comprehensive manner. The QSTS simulations are applied to a set of sample feeders with high PV deployment to illustrate the usefulness of the approach. The report describes methods that can help determine how PV affects distribution system operations. The simulation results are focused on enhancing the understanding of the underlying technical issues. The examples also highlight the steps needed to perform QSTS simulation and describe the data needed to drive the simulations. The goal of this report is to make the methodology of time series power flow analysis readily accessible to utilities and others responsible for evaluating potential PV impacts.

Broderick, Robert Joseph; Quiroz, Jimmy Edward; Ellis, Abraham; Reno, Matthew J. [Georgia Institute of Technology, Atlanta, GA; Smith, Jeff [Electric Power Research Institute, Knoxville, TN; Dugan, Roger [Electric Power Research Institute, Knoxville, TN

2013-01-01

249

Fitting the void: Data boundaries, point distributions and strain analysis  

NASA Astrophysics Data System (ADS)

An objective method is developed for identifying the shape of the void generated by analysis of the spatial arrangement of point distributions using the Fry method and in particular Delaunay triangulation nearest neighbour data. The method works by numerically minimising a weighted non-linear least-squares formulation which tends to selectively apply higher weights to points below the boundary and less weight to points above the boundary. Sampling errors are estimated using a bootstrap procedure. A simulation study indicates that the method works best for closely packed object arrangements and tends to underestimate the strain axial ratio at high imposed strains. Overall the method is found to be objective and consistent.

Mulchrone, Kieran F.

2013-01-01

250

The Robustness of the Student T Test when Sampling from A Weibull Distribution.  

National Technical Information Service (NTIS)

When testing with the t-test, it is assumed that the sample under investigation is from a normal population. The purpose of this thesis is to examine the sensitivity of the t-test to violations of this normality assumption. A computer simulation was perfo...

D. P. Allen

1970-01-01

251

COMPARISON OF THE WEIBULL MODEL WITH MEASURED WIND SPEED DISTRIBUTIONS FOR STOCHASTIC WIND GENERATION  

Technology Transfer Automated Retrieval System (TEKTRAN)

Wind is the principal driver of the Wind Erosion Prediction System (WEPS), which is a process-based computer model for the simulation of wind blown sediment loss from a field. WEPS generates wind using a stochastic wind generator. The objectives of this study were to improve the stochastic generati...

252

Failure-Censored Variables-Sampling Plans for Lognormal and Weibull Distributions  

Microsoft Academic Search

Variables-sampling plans arc more efficient than attributes-sampling plans. If the quality characteristic is the life of a product. however, variables sampling can be very time consuming and expensive. To save time and money, tests can be terminated before all test units have failed. This article discusses the design of variables-sampling plans based on failure-censored samples. This method of design can

Helmut Schneider

1989-01-01

253

Application of Wigner distribution function for analysis of radio occultations  

NASA Astrophysics Data System (ADS)

We present the Wigner distribution function (WDF) as an alternative to radio holographic (RH) analysis in the interpretation of radio occultation (RO) observations of the Earth's atmosphere. RH analysis is widely used in RO retrieval to isolate signal from noise and to identify atmospheric multipath. The same task is performed by WDF which also maps a 1-D wave function to 2-D time-frequency phase space and which has maxima located at the ray manifold. Unlike the standard RH technique based on the spectrum analysis in small sliding apertures, WDF is given by a global integral transform, which allows for a higher resolution. We present a tomographic derivation of the WDF and discuss its properties. Examples of analysis of simulations and COSMIC RO data show that WDF allows for a much sharper localization of the details of bending angle profiles as compared to the standard RH analysis in sliding apertures. Both WDF and RH allow for identification of multivalued bending angle profiles arising in the presence of strong horizontal gradients and may introduce a negative bias into bending angle retrieval.

Gorbunov, M. E.; Lauritsen, K. B.; Leroy, S. S.

2010-12-01

254

Calibration of Boltzmann distribution priors in Bayesian data analysis  

NASA Astrophysics Data System (ADS)

The Boltzmann distribution is commonly used as a prior probability in Bayesian data analysis. Examples include the Ising model in statistical image analysis and the canonical ensemble based on molecular dynamics force fields in protein structure calculation. These models involve a temperature or weighting factor that needs to be inferred from the data. Bayesian inference stipulates to determine the temperature based on the model evidence. This is challenging because the model evidence, a ratio of two high-dimensional normalization integrals, cannot be calculated analytically. We outline a replica-exchange Monte Carlo scheme that allows us to estimate the model evidence by use of multiple histogram reweighting. The method is illustrated for an Ising model and examples in protein structure determination.

Mechelke, Martin; Habeck, Michael

2012-12-01

255

Distributed problem solving in seismic event analysis: Final report  

SciTech Connect

The accuracy of analyses for seismic events visible to more than one monitoring station can be improved by combining data from several stations and ''triangulating'' analyses. This sort of analysis is a natural candidate for distributed problem-solving approaches. Data from different stations must be related in both time and space, raising problems of reasoning from multiple perspectives toward a common interpretation. Differences in local geography and monitoring conditions will raise problems of reasoning using different knowledge and local constraints. Just which problem aspects should be the provinces of which local analyzers (the issues of problem decomposition and task allocation) are uncertain. We proposed to investigate how emerging research on to these questions may be applied to seismic analysis in particular.

Gasser, L.

1987-01-01

256

Analysis of Fuel Ethanol Transportation Activity and Potential Distribution Constraints  

SciTech Connect

This paper provides an analysis of fuel ethanol transportation activity and potential distribution constraints if the total 36 billion gallons of renewable fuel use by 2022 is mandated by EPA under the Energy Independence and Security Act (EISA) of 2007. Ethanol transport by domestic truck, marine, and rail distribution systems from ethanol refineries to blending terminals is estimated using Oak Ridge National Laboratory s (ORNL s) North American Infrastructure Network Model. Most supply and demand data provided by EPA were geo-coded and using available commercial sources the transportation infrastructure network was updated. The percentage increases in ton-mile movements by rail, waterways, and highways in 2022 are estimated to be 2.8%, 0.6%, and 0.13%, respectively, compared to the corresponding 2005 total domestic flows by various modes. Overall, a significantly higher level of future ethanol demand would have minimal impacts on transportation infrastructure. However, there will be spatial impacts and a significant level of investment required because of a considerable increase in rail traffic from refineries to ethanol distribution terminals.

Das, Sujit [ORNL; Peterson, Bruce E [ORNL; Chin, Shih-Miao [ORNL

2010-01-01

257

Biaxial flexural strength distribution of thin ceramic substrates with surface defects  

Microsoft Academic Search

The statistical models of the strength of thin ceramic substrates with surface defects under piston-on-3-ball loading conditions are formulated using Batdorf’s statistical theory and Kirstein and Woolley’s moment equations. These models possess the form of a Weibull distribution function, making it possible to process the piston-on-3-ball biaxial flexural strength data using a Weibull treatment. During this study, it was noted

Ming Cheng; Weinong Chen; K. R. Sridhar

2003-01-01

258

Distributed Data Analysis in the ATLAS Experiment: Challenges and Solutions  

NASA Astrophysics Data System (ADS)

The ATLAS experiment at the LHC at CERN is recording and simulating several 10's of PetaBytes of data per year. To analyse these data the ATLAS experiment has developed and operates a mature and stable distributed analysis (DA) service on the Worldwide LHC Computing Grid. The service is actively used: more than 1400 users have submitted jobs in the year 2011 and a total of more 1 million jobs run every week. Users are provided with a suite of tools to submit Athena, ROOT or generic jobs to the Grid, and the PanDA workload management system is responsible for their execution. The reliability of the DA service is high but steadily improving; Grid sites are continually validated against a set of standard tests, and a dedicated team of expert shifters provides user support and communicates user problems to the sites. This paper will review the state of the DA tools and services, summarize the past year of distributed analysis activity, and present the directions for future improvements to the system.

Elmsheuser, Johannes; van der Ster, Daniel

2012-12-01

259

Distributed Principal Component Analysis for Wireless Sensor Networks  

PubMed Central

The Principal Component Analysis (PCA) is a data dimensionality reduction tech-nique well-suited for processing data from sensor networks. It can be applied to tasks like compression, event detection, and event recognition. This technique is based on a linear trans-form where the sensor measurements are projected on a set of principal components. When sensor measurements are correlated, a small set of principal components can explain most of the measurements variability. This allows to significantly decrease the amount of radio communication and of energy consumption. In this paper, we show that the power iteration method can be distributed in a sensor network in order to compute an approximation of the principal components. The proposed implementation relies on an aggregation service, which has recently been shown to provide a suitable framework for distributing the computation of a linear transform within a sensor network. We also extend this previous work by providing a detailed analysis of the computational, memory, and communication costs involved. A com-pression experiment involving real data validates the algorithm and illustrates the tradeoffs between accuracy and communication costs.

Le Borgne, Yann-Ael; Raybaud, Sylvain; Bontempi, Gianluca

2008-01-01

260

Data intensive high energy physics analysis in a distributed cloud  

NASA Astrophysics Data System (ADS)

We show that distributed Infrastructure-as-a-Service (IaaS) compute clouds can be effectively used for the analysis of high energy physics data. We have designed a distributed cloud system that works with any application using large input data sets requiring a high throughput computing environment. The system uses IaaS-enabled science and commercial clusters in Canada and the United States. We describe the process in which a user prepares an analysis virtual machine (VM) and submits batch jobs to a central scheduler. The system boots the user-specific VM on one of the IaaS clouds, runs the jobs and returns the output to the user. The user application accesses a central database for calibration data during the execution of the application. Similarly, the data is located in a central location and streamed by the running application. The system can easily run one hundred simultaneous jobs in an efficient manner and should scale to many hundreds and possibly thousands of user jobs.

Charbonneau, A.; Agarwal, A.; Anderson, M.; Armstrong, P.; Fransham, K.; Gable, I.; Harris, D.; Impey, R.; Leavett-Brown, C.; Paterson, M.; Podaima, W.; Sobie, R. J.; Vliet, M.

2012-02-01

261

Implementation of force distribution analysis for molecular dynamics simulations  

PubMed Central

Background The way mechanical stress is distributed inside and propagated by proteins and other biopolymers largely defines their function. Yet, determining the network of interactions propagating internal strain remains a challenge for both, experiment and theory. Based on molecular dynamics simulations, we developed force distribution analysis (FDA), a method that allows visualizing strain propagation in macromolecules. Results To be immediately applicable to a wide range of systems, FDA was implemented as an extension to Gromacs, a commonly used package for molecular simulations. The FDA code comes with an easy-to-use command line interface and can directly be applied to every system built using Gromacs. We provide an additional R-package providing functions for advanced statistical analysis and presentation of the FDA data. Conclusions Using FDA, we were able to explain the origin of mechanical robustness in immunoglobulin domains and silk fibers. By elucidating propagation of internal strain upon ligand binding, we previously also successfully revealed the functionality of a stiff allosteric protein. FDA thus has the potential to be a valuable tool in the investigation and rational design of mechanical properties in proteins and nano-materials.

2011-01-01

262

Support vector machine optimization via margin distribution analysis  

NASA Astrophysics Data System (ADS)

Support Vector Machines (SVMs) have generated excitement and interest in the pattern recognition community due to their generalization, performance, and ability to operate in high dimensional feature spaces. Although SVMs are generated without the use of user-specified models, required hyperparameters, such as Gaussian kernel width, are usually user-specified and/or experimentally derived. This effort presents an alternative approach for the selection of the Gaussian kernel width via analysis of the distributional characteristics of the training data projected on the ‘trained" SVM (margin values). The efficacy of a particular kernel width can be visually determined via one-dimensional density estimate plots of the training data margin values. Projecting the data onto the SVM hyperplane allows the one-dimensional analysis of the data from the viewpoint of the ‘trained" SVM. The effect of kernel parameter selection on class-conditional margin distributions is demonstrated in the one-dimensional projection subspace, and a criterion for unsupervised optimization of kernel width is discussed. Empirical results are given for two classification problems: the ‘toy" checkerboard problem and a high dimensional classification problem using simulated High-Resolution Radar (HRR) targets projected into a wavelet packet feature space.

Waagen, Donald; Cassabaum, Mary; Schmitt, Harry A.; Pollock, Bruce

2003-09-01

263

Summarizing CSP Hardness with Continuous Probability Distributions  

Microsoft Academic Search

We present empirical evidence that the distribution ofeffort required to solve CSPs randomly generated atthe 50% satisfiable point, when using a backtrackingalgorithm, can be approximated by two standard familiesof continuous probability distribution functions.Solvable problems can be modelled by the Weibull distribution,and unsolvable problems by the lognormaldistribution. These distributions fit equally well overa variety of backtracking based algorithms.1. IntroductionSeveral key...

Daniel Frost; Irina Rish; Lluís Vila

1997-01-01

264

Time-frequency-distribution analysis of frequency dispersive targets  

NASA Astrophysics Data System (ADS)

In the analysis of scattering targets, it is common to obtain time domain profiles by a Fourier transformation of the frequency response. In this process, wide-band frequency data are used to generate an approximation of the impulse response of the target via an inverse Fourier transform (IFT). The peaks in this impulse response then correspond to scattering centers of the target. In this paper, the authors show that an analysis of scattering from frequency dispersive structures can be accomplished by time-frequency distribution (TFD) techniques. Three TFDs are investigated, and applied to the scattering analysis of a circular waveguide cavity. This paper comprises a brief description of the applied TFDs, and a detailed comparison of the TFD results for scattering analysis. We shall show that for some targets, such as the cavity, TFD is an effective method for description of the properties of the target. For the waveguide cavity, propagating modes and cutoff frequencies can readily be determined from the TFD, whereas neither time nor frequency representations will provide such information.

Walton, E. K.; Moghaddar, A.

1993-01-01

265

Evaluation of Distribution Analysis Software for DER Applications  

SciTech Connect

The term ''Distributed energy resources'' or DER refers to a variety of compact, mostly self-contained power-generating technologies that can be combined with energy management and storage systems and used to improve the operation of the electricity distribution system, whether or not those technologies are connected to an electricity grid. Implementing DER can be as simple as installing a small electric generator to provide backup power at an electricity consumer's site. Or it can be a more complex system, highly integrated with the electricity grid and consisting of electricity generation, energy storage, and power management systems. DER devices provide opportunities for greater local control of electricity delivery and consumption. They also enable more efficient utilization of waste heat in combined cooling, heating and power (CHP) applications--boosting efficiency and lowering emissions. CHP systems can provide electricity, heat and hot water for industrial processes, space heating and cooling, refrigeration, and humidity control to improve indoor air quality. DER technologies are playing an increasingly important role in the nation's energy portfolio. They can be used to meet base load power, peaking power, backup power, remote power, power quality, as well as cooling and heating needs. DER systems, ranging in size and capacity from a few kilowatts up to 50 MW, can include a number of technologies (e.g., supply-side and demand-side) that can be located at or near the location where the energy is used. Information pertaining to DER technologies, application solutions, successful installations, etc., can be found at the U.S. Department of Energy's DER Internet site [1]. Market forces in the restructured electricity markets are making DER, both more common and more active in the distribution systems throughout the US [2]. If DER devices can be made even more competitive with central generation sources this trend will become unstoppable. In response, energy providers will be forced to both fully acknowledge the trend and plan for accommodating DER [3]. With bureaucratic barriers [4], lack of time/resources, tariffs, etc. still seen in certain regions of the country, changes still need to be made. Given continued technical advances in DER, the time is fast approaching when the industry, nation-wide, must not only accept DER freely but also provide or review in-depth technical assessments of how DER should be integrated into and managed throughout the distribution system. Characterization studies are needed to fully understand how both the utility system and DER devices themselves will respond to all reasonable events (e.g., grid disturbances, faults, rapid growth, diverse and multiple DER systems, large reactive loads). Some of this work has already begun as it relates to operation and control of DER [5] and microturbine performance characterization [6,7]. One of the most urgently needed tools that can provide these types of analyses is a distribution network analysis program in combination with models for various DER. Together, they can be used for (1) analyzing DER placement in distribution networks and (2) helping to ensure that adequate transmission reliability is maintained. Surveys of the market show products that represent a partial match to these needs; specifically, software that has been developed to plan electrical distribution systems and analyze reliability (in a near total absence of DER). The first part of this study (Sections 2 and 3 of the report) looks at a number of these software programs and provides both summary descriptions and comparisons. The second part of this study (Section 4 of the report) considers the suitability of these analysis tools for DER studies. It considers steady state modeling and assessment work performed by ORNL using one commercially available tool on feeder data provided by a southern utility. Appendix A provides a technical report on the results of this modeling effort.

Staunton, RH

2003-01-23

266

How skew distributions emerge in evolving systems  

NASA Astrophysics Data System (ADS)

Despite the ubiquitous emergence of skew distributions such as power law, log-normal, and Weibull distributions, there still lacks proper understanding of the mechanism as well as relations between them. It is studied how such distributions emerge in general evolving systems and what makes the difference between them. Beginning with a master equation for general evolving systems, we obtain the time evolution equation for the size distribution function. Obtained in the case of size changes proportional to the current size are the power law stationary distribution with an arbitrary exponent and the evolving distribution, which is of either log-normal or Weibull type asymptotically, depending on production and growth in the system. This master equation approach thus gives a unified description of those three types of skew distribution observed in a variety of systems, providing physical derivation of them and disclosing how they are related.

Choi, M. Y.; Choi, H.; Fortin, J.-Y.; Choi, J.

2009-02-01

267

Failure Analysis of Three Si3N4 Balls.  

National Technical Information Service (NTIS)

A test series was undertaken to demonstrate the rolling-element fatigue life and Weibull distribution of advanced material bearings compared with conventional 52100 steel bearings. The candidate advanced material bearing consisted of Norton Si3N4 NBD-200 ...

M. J. O'Brien N. Presser

2001-01-01

268

Silk Fiber Mechanics from Multiscale Force Distribution Analysis  

PubMed Central

Here we decipher the molecular determinants for the extreme toughness of spider silk fibers. Our bottom-up computational approach incorporates molecular dynamics and finite element simulations. Therefore, the approach allows the analysis of the internal strain distribution and load-carrying motifs in silk fibers on scales of both molecular and continuum mechanics. We thereby dissect the contributions from the nanoscale building blocks, the soft amorphous and the strong crystalline subunits, to silk fiber mechanics. We identify the amorphous subunits not only to give rise to high elasticity, but to also ensure efficient stress homogenization through the friction between entangled chains, which also allows the crystals to withstand stresses as high as 2 GPa in the context of the amorphous matrix. We show that the maximal toughness of silk is achieved at 10–40% crystallinity depending on the distribution of crystals in the fiber. We also determined a serial arrangement of the crystalline and amorphous subunits in lamellae to outperform a random or a parallel arrangement, putting forward what we believe to be a new structural model for silk and other semicrystalline materials. The multiscale approach, not requiring any empirical parameters, is applicable to other partially ordered polymeric systems. Hence, it is an efficient tool for the design of artificial silk fibers.

Cetinkaya, Murat; Xiao, Senbo; Markert, Bernd; Stacklies, Wolfram; Grater, Frauke

2011-01-01

269

SATMC: Spectral energy distribution Analysis Through Markov Chains  

NASA Astrophysics Data System (ADS)

We present the general purpose spectral energy distribution (SED) fitting tool SED Analysis Through Markov Chains (SATMC). Utilizing Monte Carlo Markov Chain (MCMC) algorithms, SATMC fits an observed SED to SED templates or models of the user's choice to infer intrinsic parameters, generate confidence levels and produce the posterior parameter distribution. Here, we describe the key features of SATMC from the underlying MCMC engine to specific features for handling SED fitting. We detail several test cases of SATMC, comparing results obtained from traditional least-squares methods, which highlight its accuracy, robustness and wide range of possible applications. We also present a sample of submillimetre galaxies (SMGs) that have been fitted using the SED synthesis routine GRASIL as input. In general, these SMGs are shown to occupy a large volume of parameter space, particularly in regards to their star formation rates which range from ˜30 to 3000 M? yr-1 and stellar masses which range from ˜1010 to 1012 M?. Taking advantage of the Bayesian formalism inherent to SATMC, we also show how the fitting results may change under different parametrizations (i.e. different initial mass functions) and through additional or improved photometry, the latter being crucial to the study of high-redshift galaxies.

Johnson, S. P.; Wilson, G. W.; Tang, Y.; Scott, K. S.

2013-10-01

270

Phylogenetic analysis reveals a scattered distribution of autumn colours  

PubMed Central

Background and Aims Leaf colour in autumn is rarely considered informative for taxonomy, but there is now growing interest in the evolution of autumn colours and different hypotheses are debated. Research efforts are hindered by the lack of basic information: the phylogenetic distribution of autumn colours. It is not known when and how autumn colours evolved. Methods Data are reported on the autumn colours of 2368 tree species belonging to 400 genera of the temperate regions of the world, and an analysis is made of their phylogenetic relationships in order to reconstruct the evolutionary origin of red and yellow in autumn leaves. Key Results Red autumn colours are present in at least 290 species (70 genera), and evolved independently at least 25 times. Yellow is present independently from red in at least 378 species (97 genera) and evolved at least 28 times. Conclusions The phylogenetic reconstruction suggests that autumn colours have been acquired and lost many times during evolution. This scattered distribution could be explained by hypotheses involving some kind of coevolutionary interaction or by hypotheses that rely on the need for photoprotection.

Archetti, Marco

2009-01-01

271

Phylogenetic analysis on the soil bacteria distributed in karst forest  

PubMed Central

Phylogenetic composition of bacterial community in soil of a karst forest was analyzed by culture-independent molecular approach. The bacterial 16S rRNA gene was amplified directly from soil DNA and cloned to generate a library. After screening the clone library by RFLP, 16S rRNA genes of representative clones were sequenced and the bacterial community was analyzed phylogenetically. The 16S rRNA gene inserts of 190 clones randomly selected were analyzed by RFLP and generated 126 different RFLP types. After sequencing, 126 non-chimeric sequences were obtained, generating 113 phylotypes. Phylogenetic analysis revealed that the bacteria distributed in soil of the karst forest included the members assigning into Proteobacteria, Acidobacteria, Planctomycetes, Chloroflexi (Green nonsulfur bacteria), Bacteroidetes, Verrucomicrobia, Nitrospirae, Actinobacteria (High G+C Gram-positive bacteria), Firmicutes (Low G+C Gram-positive bacteria) and candidate divisions (including the SPAM and GN08).

Zhou, JunPei; Huang, Ying; Mo, MingHe

2009-01-01

272

Order statistics from the type i generalized logistic distribution  

Microsoft Academic Search

In this paper, we first obtain three generalized forms of the standard logistic distribution. These are derived by compounding an extreme-value distribution of the doubly exponential type, a reduced log-Weibull distribution and an exponential-gamma distribution, respectively, with a gamma distribution. The usefulness of these three types of generalized logistic distributions in some estimation problems, and also in some robustness studies,

N. Balakrishnan; M. Y. Leung

1988-01-01

273

Distribution System Voltage Performance Analysis for High-Penetration PV  

Microsoft Academic Search

Distributed generation can have an impact on distribution feeder voltage regulation, and distributed solar photovoltaics (PV) are no exception. As the penetration level of solar PV rises over the coming decades, reverse power flow on the distribution feeder will happen more frequently and the associated voltage rise might lead to violations of voltage boundaries defined by ANSI C84.1. The severity

Y. Liu; J. Bebic; B. Kroposki; J. de Bedout; W. Ren

2008-01-01

274

Extending Statistics of Extremes to Distributions Varying in Position and Scale and the Implications for Race Models  

Microsoft Academic Search

Race models are characterized by the largest or smallest of samples from n distributions. The asymptotic theory of extremes has demonstrated that for identically distributed, independent, and lower-bounded random variables, whose left tail approximates a power function, the distribution of the minimum tends toward a Weibull distribution as n increases. In this article, we remove the restriction of identically distributed

Denis Cousineau; Victor W. Goodman; Richard M. Shiffrin

2002-01-01

275

Detailed End Use Load Modeling for Distribution System Analysis  

SciTech Connect

The field of distribution system analysis has made significant advances in the past ten years. It is now standard practice when performing a power flow simulation to use an algorithm that is capable of unbalanced per-phase analysis. Recent work has also focused on examining the need for time-series simulations instead of examining a single time period, i.e., peak loading. One area that still requires a significant amount of work is the proper modeling of end use loads. Currently it is common practice to use a simple load model consisting of a combination of constant power, constant impedance, and constant current elements. While this simple form of end use load modeling is sufficient for a single point in time, the exact model values are difficult to determine and it is inadequate for some time-series simulations. This paper will examine how to improve simple time invariant load models as well as develop multi-state time variant models.

Schneider, Kevin P.; Fuller, Jason C.

2010-04-09

276

Unsymmetrical Short-Circuit Fault Analysis for Weakly Meshed Distribution Systems  

Microsoft Academic Search

Due to the integration of distributed generations and the realization of smart grids, most radial distribution systems would become weakly meshed in the near future. Thus, this paper proposes an efficient and accurate short-circuit fault-analysis method for unbalanced weakly meshed distribution systems. Two proposed matrices developed from the radial and weakly meshed characteristics of distribution systems are used to analyze

Jen-Hao Teng

2010-01-01

277

Mixed methods for fitting the GEV distribution  

Microsoft Academic Search

The generalized extreme-value (GEV) distribution is widely used for modeling and characterizing extremes. It is a flexible three-parameter distribution that combines three extreme-value distributions within a single framework: the Gumbel, Frechet, and Weibull. Common methods used for estimating the GEV parameters are the method of maximum likelihood and the method of L-moments. This paper generalizes the mixed maximum likelihood and

Pierre Ailliot; Craig Thompson; Peter Thomson

2011-01-01

278

On Distributed Computing Systems Reliability Analysis Under Program Execution Constraints  

Microsoft Academic Search

Presents an algorithm for computing the reliability of distributed computing systems (DCS). The algorithm, called the Fast Reliability Evaluation Algorithm, is based on the factoring theorem employing several reliability preserving reduction techniques. The effect of file distributions, program distributions, and various topologies on reliability of the DCS is studied in detail using the proposed algorithm. Compared with existing algorithms on

Deng-jyi Chen; Min-sheng Lin

1994-01-01

279

Prediction of the Inert Strength Distribution of Si3N4 Diesel Valves  

SciTech Connect

Censored Weibull strength distributions were generated with NT551 silicon nitride four-point flexure data using the ASTM C1161-B and 5.0 mm diameter cylindrical specimens. Utilizing finite element models and AlliedSignal's life prediction codes, the inert or fast fracture strength failure probability of a ceramic diesel valve was estimated from these data sets. The failure probability prediction derived from each data set were found to be more conservative than valve strength data. Fractographic analysis of the test specimens and valves showed that the cylindrical specimens failed from a different flaw population than the prismatic flexure bars and the valves. The study emphasizes the prerequisite of having coincident flaw populations homogeneously distributed in both the test specimen and the ceramic component. Lastly, it suggests that unless material homogeneity exists, that any meaningful life prediction or reliability analysis of a component may not be possible.

Andrews, M.J.; Breder, K.; Wereszczak, A.A.

1999-01-25

280

Comparison of the thermal inactivation of Bacillus subtilis spores in foods using the modified Weibull and Bigelow equations  

Microsoft Academic Search

The association of a modified Weibull model and Bigelow model was applied to the thermal inactivation of Bacillus subtilis spores heated in phosphate buffer, milk, kayu (a Japanese style rice porridge) and soy sauce as well. The inactivation kinetics presented a light downward concave profile, the acidic pH increased the efficiency of the heat treatment but on the opposite, lesser

A. Jagannath; T. Tsuchido; J.-M. Membré

2005-01-01

281

Exploring generalized probability weighted moments, generalized moments and maximum likelihood estimating methods in two-parameter Weibull model  

Microsoft Academic Search

Generalized probability weighted moments (GPWM), generalized moments and maximum likelihood (ML) estimating methods are investigated in the two-parameter Weibull (WEI) model. Point estimators for positive and negative shape parameters and for quantiles with special return periods are derived. Analytical expressions for the asymptotic variances of the estimators are presented. Simulation results on the performance of the three estimating methods are

Smail Mahdi; Fahim Ashkar

2004-01-01

282

Distribution and Phylogenetic Analysis of Family 19 Chitinases in Actinobacteria  

PubMed Central

In organisms other than higher plants, family 19 chitinase was first discovered in Streptomyces griseus HUT6037, and later, the general occurrence of this enzyme in Streptomyces species was demonstrated. In the present study, the distribution of family 19 chitinases in the class Actinobacteria and the phylogenetic relationship of Actinobacteria family 19 chitinases with family 19 chitinases of other organisms were investigated. Forty-nine strains were chosen to cover almost all the suborders of the class Actinobacteria, and chitinase production was examined. Of the 49 strains, 22 formed cleared zones on agar plates containing colloidal chitin and thus appeared to produce chitinases. These 22 chitinase-positive strains were subjected to Southern hybridization analysis by using a labeled DNA fragment corresponding to the catalytic domain of ChiC, and the presence of genes similar to chiC of S. griseus HUT6037 in at least 13 strains was suggested by the results. PCR amplification and sequencing of the DNA fragments corresponding to the major part of the catalytic domains of the family 19 chitinase genes confirmed the presence of family 19 chitinase genes in these 13 strains. The strains possessing family 19 chitinase genes belong to 6 of the 10 suborders in the order Actinomycetales, which account for the greatest part of the Actinobacteria. Phylogenetic analysis suggested that there is a close evolutionary relationship between family 19 chitinases found in Actinobacteria and plant class IV chitinases. The general occurrence of family 19 chitinase genes in Streptomycineae and the high sequence similarity among the genes found in Actinobacteria suggest that the family 19 chitinase gene was first acquired by an ancestor of the Streptomycineae and spread among the Actinobacteria through horizontal gene transfer.

Kawase, Tomokazu; Saito, Akihiro; Sato, Toshiya; Kanai, Ryo; Fujii, Takeshi; Nikaidou, Naoki; Miyashita, Kiyotaka; Watanabe, Takeshi

2004-01-01

283

A distributed model of solid waste anaerobic digestion: sensitivity analysis.  

PubMed

A distributed model of anaerobic digestion of solid waste was developed to describe the balance between the rates of polymer hydrolysis and methanogenesis during the anaerobic conversion of rich and lean wastes in batch and continuous-flow reactors. Waste, volatile fatty acids (VFAs), methanogenic biomass and sodium concentrations are the model variables. Diffusion and advection of VFAs inhibiting both polymer hydrolysis and methanogenesis were considered. A sensitivity analysis by changing the key model parameter values was carried out. The model simulations showed that the effective distance between the areas of hydrolysis/acidogenesis and methanogenesis is very important. An initial spatial separation of rich waste and inoculum enhances the methane production and waste degradation at high waste loading if relatively low VFA diffusion into the methanogenic area is taking place. When both hydrolysis and methanogenesis are strongly inhibited by high levels of VFA, fluctuations in biomass concentration are thought to be responsible for initiating the expansion of methanogenic area over the reactor space. PMID:14531433

Vavilin, V A; Rytov, S V; Pavlostathis, S G; Jokela, J; Rintala, J

2003-01-01

284

On estimating crystal shape for crystal size distribution analysis  

NASA Astrophysics Data System (ADS)

The accurate determination of three-dimensional crystal habit (long intermediate short axis) is a requirement to enable correct stereological conversion of 2D crystal size measurements to true 3D crystal size distributions (CSDs). In this contribution, we introduce a database and spreadsheet program which provides an objective estimate of true crystal habit from raw 2D measurements. The database compares the sample's 2D measurements with 2D shape curves for random sections through 703 different habits. The output gives the five best-match curves and corresponding crystal habits based on a least-squares fit between sample and database. The minimum sample size required to give good shape estimates from 2D data is tested using random runs of sections through known shapes with different population densities. At minimum, 75 crystal sections are required to robustly determine crystal habit for CSD measurements if crystals are tabular in shape, with more acicular shapes requiring a minimum of 250 sections, suggesting a sample size of > 250 sections to be used for shape determination in natural examples where the true 3D shape is unknown. The crystal habit of the best-match shape can then be used to provide a more robust CSD analysis, which in turn can be used to investigate magmatic processes with more certainty.

Morgan, Dan J.; Jerram, Dougal A.

2006-06-01

285

Clustering Analysis of Seismicity and Aftershock Identification  

NASA Astrophysics Data System (ADS)

We introduce a statistical methodology for clustering analysis of seismicity in the time-space-energy domain and use it to establish the existence of two statistically distinct populations of earthquakes: clustered and nonclustered. This result can be used, in particular, for nonparametric aftershock identification. The proposed approach expands the analysis of Baiesi and Paczuski [Phys. Rev. EPLEEE81063-651X 69, 066106 (2004)10.1103/PhysRevE.69.066106] based on the space-time-magnitude nearest-neighbor distance ? between earthquakes. We show that for a homogeneous Poisson marked point field with exponential marks, the distance ? has the Weibull distribution, which bridges our results with classical correlation analysis for point fields. The joint 2D distribution of spatial and temporal components of ? is used to identify the clustered part of a point field. The proposed technique is applied to several seismicity models and to the observed seismicity of southern California.

Zaliapin, Ilya; Gabrielov, Andrei; Keilis-Borok, Vladimir; Wong, Henry

2008-07-01

286

Analysis of current distribution in a large superconductor  

Microsoft Academic Search

An imbalanced current distribution which is often observed in cable-in-conduit (CIC) superconductors composed of multistaged, triplet type sub-cables, can deteriorate the performance of the coils. It is, hence very important to analyze the current distribution in a superconductor and find out methods to realize a homogeneous current distribution in the conductor. We apply magnetic flux conservation in a loop contoured

Takataro Hamajima; A. K. M. Alamgir; Naoyuki Harada; Makoto Tsuda; Michitaka Ono; Hirohisa Takano

2000-01-01

287

An Analysis of the U.S. Distribution System  

Microsoft Academic Search

This paper forms part of an OECD project which addressed the issue of the structure and change in the distribution systems of seven OECD countries.The paper begins with a conceptual framework describing the functions, market outcomes and economic implications of the distribution sector. Next, it gives an overview of the U.S. distribution system in the 1980s. In particular, it discusses

Roger R. Betancourt

1993-01-01

288

How extreme is extreme? An assessment of daily rainfall distribution tails  

NASA Astrophysics Data System (ADS)

The upper part of a probability distribution, usually known as the tail, governs both the magnitude and the frequency of extreme events. The tail behaviour of all probability distributions may be, loosely speaking, categorized into two families: heavy-tailed and light-tailed distributions, with the latter generating "milder" and less frequent extremes compared to the former. This emphasizes how important for hydrological design it is to assess the tail behaviour correctly. Traditionally, the wet-day daily rainfall has been described by light-tailed distributions like the Gamma distribution, although heavier-tailed distributions have also been proposed and used, e.g., the Lognormal, the Pareto, the Kappa, and other distributions. Here we investigate the distribution tails for daily rainfall by comparing the upper part of empirical distributions of thousands of records with four common theoretical tails: those of the Pareto, Lognormal, Weibull and Gamma distributions. Specifically, we use 15 029 daily rainfall records from around the world with record lengths from 50 to 172 yr. The analysis shows that heavier-tailed distributions are in better agreement with the observed rainfall extremes than the more often used lighter tailed distributions. This result has clear implications on extreme event modelling and engineering design.

Papalexiou, S. M.; Koutsoyiannis, D.; Makropoulos, C.

2013-02-01

289

Analysis of lightning-caused distribution transformer failures  

Microsoft Academic Search

This paper investigates the effects of direct strokes to medium-voltage (MV) lines by analyzing the surges at the primary and secondary sides of a single-phase distribution transformer installed in a typical rural network of the state of Rio Grande do Sul, located in the South of Brazil. The distribution transformers of AES Sul, the electric utility, present a high failure

T. O. de Carvalho; A. Piantini; P. F. Obase; J. M. Janiszewski; E. L. Batista

2011-01-01

290

Runs of geometrically distributed random variables: a probabilistic analysis  

NASA Astrophysics Data System (ADS)

Using a Markov chain approach and a polyomino-like description, we study some asymptotic properties of runs of geometrically distributed random variables. We analyze the limiting trajectories, the number of runs and the run length distribution, the hitting time to a length k run and the maximum run length.

Louchard, Guy

2002-05-01

291

Network secondary distribution system fault current analysis and application  

Microsoft Academic Search

Network secondary distribution systems are typically designed to ensure sufficient current is available to clear the most severe type of fault which is the solid fault. The procedure presented in this paper analyzes a network secondary distribution system for the expected performance of secondary cable circuits during solid type faults. By satisfying the criteria presented in this paper, it is

Daniel J. Mungovan; David R. Smith

2011-01-01

292

Monotone Log-Odds Rate Distributions in Reliability Analysis  

Microsoft Academic Search

Monotone failure rate models [Barlow Richard, E., Marshall, A. W., Proschan, Frank. (1963). Properties of probability distributions with monotone failure rate. Annals of Mathematical Statistics 34:375–389, and Barlow Richard, E., Proschan, Frank. (1965). Mathematical Theory of Reliability. New York: John Wiley & Sons, Barlow Richard, E., Proschan, Frank. (1966a). Tolerance and confidence limits for classes of distributions based on failure

Yao Wang; Anwar M. Hossain; William J. Zimmer

2003-01-01

293

Analysis of charged hadron multiplicity distributions at RHIC  

Microsoft Academic Search

It is demonstrated that with Heinz's collective flow model charged particle distributions at AGS and lower SPS energies (less than 20 GeV\\/n), can successfully be analyzed, but that the model fails for the RHIC data. Heinz's model calculation underestimates the tails of the charged particle distributions from RHIC, the discrepancy becoming bigger as the energy increases. To study the multiplicity

Wei Xiong; Sheng-Qin Feng

2008-01-01

294

Analysis of Parallel Downloading for Large File Distribution  

Microsoft Academic Search

Recently, the scheme of parallel downloading (PD) has been adopted by a number of Internet file download- ing applications. With the wide deployment of content distribution networks and peer-to-peer networks, PD is expected to be more commonly used for file distribution. There have been experiments showing that PD results in higher aggregated downloading throughput and therefore shorter downloading time experienced

Simon G. M. Koo; Catherine Rosenberg; Dongyan Xu

2003-01-01

295

Emergence of skew distributions in controlled growth processes  

NASA Astrophysics Data System (ADS)

Starting from a master equation, we derive the evolution equation for the size distribution of elements in an evolving system, where each element can grow, divide into two, and produce new elements. We then probe general solutions of the evolution equation, to obtain such skew distributions as power-law, log-normal, and Weibull distributions, depending on the growth or division and production. Specifically, repeated production of elements of uniform size leads to power-law distributions, whereas production of elements with the size distributed according to the current distribution as well as no production of new elements results in log-normal distributions. Finally, division into two, or binary fission, bears Weibull distributions. Numerical simulations are also carried out, confirming the validity of the obtained solutions.

Goh, Segun; Kwon, H. W.; Choi, M. Y.; Fortin, J.-Y.

2010-12-01

296

Distribution automation system with real-time analysis tools  

SciTech Connect

In the past 10 years, the electric power industry`s involvement in distribution automation (DA) has been principally focused on remote monitoring and control of the distribution systems and their equipment. SCADA has constituted the most significant attribute. Electric utilities in many locations around the world have installed numerous SCADA systems for their distribution substations and feeders and built the infrastructure for real-time distribution operation and control. Real-time data is available to human operators, enabling them to monitor more and more events in their distribution systems and to control automatic equipment remotely. At the same time, the added volume of real-time data has also created data overloads at some distribution control centers. Without proper decision support tools, operators could only rely on their past experience in making operating decisions based on a subset of the data they receive. As a result, large volumes of real-time data along with much of the infrastructure built for automatic operation of the distribution systems could remain underutilized. This article features PG and E`s approach to utilizing the existing infrastructures and available data more effectively by introducing intelligence to DA/SCADA systems through development of advanced analytical tools for operations decision support.

Shirmohammadi, D. [Shir Consultants, San Ramon, CA (United States); Liu, W.H.E.; Lau, K.C. [Pacific Gas and Electric Co., San Ramon, CA (United States); Hong, H.W. [Opercon Systems, Inc., Alameda, CA (United States)

1996-04-01

297

Statistical analysis of the electrical breakdown time delay distributions in krypton  

SciTech Connect

The statistical analysis of the experimentally observed electrical breakdown time delay distributions in the krypton-filled diode tube at 2.6 mbar is presented. The experimental distributions are obtained on the basis of 1000 successive and independent measurements. The theoretical electrical breakdown time delay distribution is evaluated as the convolution of the statistical time delay with exponential, and discharge formative time with Gaussian distribution. The distribution parameters are estimated by the stochastic modelling of the time delay distributions, and by comparing them with the experimental distributions for different relaxation times, voltages, and intensities of UV radiation. The transition of distribution shapes, from Gaussian-type to the exponential-like, is investigated by calculating the corresponding skewness and excess kurtosis parameters. It is shown that the mathematical model based on the convolution of two random variable distributions describes experimentally obtained time delay distributions and the separation of the total breakdown time delay to the statistical and formative time delay.

Maluckov, Cedomir A.; Karamarkovic, Jugoslav P.; Radovic, Miodrag K.; Pejovic, Momcilo M. [Technical Faculty in Bor, University of Belgrade, Vojske Jugoslavije 24, 19210 Bor (Serbia and Montenegro); Faculty of Civil Engineering and Architecture, University of Nis, Beogradska 14, 18000 Nis (Serbia and Montenegro); Faculty of Sciences and Mathematics, University of Nis, P.O. Box 224, 18001 Nis (Serbia and Montenegro); Faculty of Electronic Engineering, University of Nis, P.O. Box 73, 18001 Nis (Serbia and Montenegro)

2006-08-15

298

Experiences on implementation of GIS based tools for analysis, planning and design of distribution systems  

Microsoft Academic Search

Geo-spatial information system (GIS) is a powerful tool to Visualize distribution network as it exists on ground. GIS based electrical distribution network analysis & design tools enables the planning engineer to visualize the areas of low voltages and high losses; reconfigure network for reduction of losses in planning mode, design of distribution network to extend supply to new customers and

M. V. K. Rao; B. S. Varma; C. Radhakrishna

2008-01-01

299

Statistical analysis of electrical breakdown time delay distributions in neon tube at 13.3 mbar  

Microsoft Academic Search

Results of the statistical analysis of the electrical breakdown time delay for a neon-filled tube at 13.3 mbar are presented in this paper. Experimental distributions of the breakdown time delay were established on the basis of 1000 successive and independent measurements, deviating from usual exponential distribution. Breakdown time delay distributions are numerically generated from the composition of two parameters, which

Cedomir A. Maluckov; Jugoslav P. Karamarkovic; M. K. Radovic

2003-01-01

300

Statistical analysis of the electrical breakdown time delay distributions in krypton  

Microsoft Academic Search

The statistical analysis of the experimentally observed electrical breakdown time delay distributions in the krypton-filled diode tube at 2.6 mbar is presented. The experimental distributions are obtained on the basis of 1000 successive and independent measurements. The theoretical electrical breakdown time delay distribution is evaluated as the convolution of the statistical time delay with exponential, and discharge formative time with

Jugoslav P. Karamarkovic´; Miodrag K. Radovic´

2006-01-01

301

Bayesian estimation of generalized exponential distribution under noninformative priors  

NASA Astrophysics Data System (ADS)

The generalized exponential distribution, proposed by Gupta and Kundu (1999), is a good alternative to standard lifetime distributions as exponential, Weibull or gamma. Several authors have considered the problem of Bayesian estimation of the parameters of generalized exponential distribution, assuming independent gamma priors and other informative priors. In this paper, we consider a Bayesian analysis of the generalized exponential distribution by assuming the conventional noninformative prior distributions, as Jeffreys and reference prior, to estimate the parameters. These priors are compared with independent gamma priors for both parameters. The comparison is carried out by examining the frequentist coverage probabilities of Bayesian credible intervals. We shown that maximal data information prior implies in an improper posterior distribution for the parameters of a generalized exponential distribution. It is also shown that the choice of a parameter of interest is very important for the reference prior. The different choices lead to different reference priors in this case. Numerical inference is illustrated for the parameters by considering data set of different sizes and using MCMC (Markov Chain Monte Carlo) methods.

Moala, Fernando Antonio; Achcar, Jorge Alberto; Tomazella, Vera Lúcia Damasceno

2012-10-01

302

On the Analysis of Composite Lumped-Distributed Systems.  

National Technical Information Service (NTIS)

Fabrication methods associated with modern microelectronic technology have stimulated detailed investigation of the properties of distributed active and passive transmission systems. As a consequence, there have appeared recently several interesting resul...

J. J. Kelly M. S. Ghausi J. H. Mulligan

1966-01-01

303

Completion report harmonic analysis of electrical distribution systems.  

National Technical Information Service (NTIS)

Harmonic currents have increased dramatically in electrical distribution systems in the last few years due to the growth in non-linear loads found in most electronic devices. Because electrical systems have been designed for linear voltage and current wav...

L. M. Tolbert

1996-01-01

304

Determination analysis of energy conservation standards for distribution transformers  

SciTech Connect

This report contains information for US DOE to use in making a determination on proposing energy conservation standards for distribution transformers as required by the Energy Policy Act of 1992. Potential for saving energy with more efficient liquid-immersed and dry-type distribution transformers could be significant because these transformers account for an estimated 140 billion kWh of the annual energy lost in the delivery of electricity. Objective was to determine whether energy conservation standards for distribution transformers would have the potential for significant energy savings, be technically feasible, and be economically justified from a national perspective. It was found that energy conservation for distribution transformers would be technically and economically feasible. Based on the energy conservation options analyzed, 3.6-13.7 quads of energy could be saved from 2000 to 2030.

Barnes, P.R.; Van Dyke, J.W.; McConnell, B.W.; Das, S.

1996-07-01

305

Diffractive parton distributions from the analysis with higher twist  

SciTech Connect

We determine diffractive parton distributions of the proton from DGLAP based fits to HERA data including the twist-4 contribution from longitudinal polarized virtual photons important in the region of large {beta}. This contribution has the biggest impact on the diffractive gluon distribution and the longitudinal structure function F{sub L}{sup D} which is going to be determined from the HERA data.

Golec-Biernat, Krzysztof [Institute of Nuclear Physics Polish Academy of Sciences, Cracow, Poland Institute of Physics, University of Rzeszow, Rzeszow (Poland)

2009-03-23

306

Optimizing the Distributed Evaluation of Stratified Programs via Structural Analysis  

Microsoft Academic Search

\\u000a The attention received by query optimization is constantly growing, but efficiently reasoning over natively distributed data\\u000a is still an open issue. Three main problems must be faced in this context: (i) rules to be processed may contain many atoms and may involve complex joins among them; (ii) the original distribution of input data is a fact and must be considered

Rosamaria Barilaro; Francesco Ricca; Giorgio Terracina

2011-01-01

307

Reliability Test Plans for Exponentiated Log-Logistic Distribution  

Microsoft Academic Search

A generalization of the log-logistic distribution called exponentiated log-logistic distribution (in lines of exponentiated Weibull distribution suggested by Mudholkar and Sri- vastava (2)) is considered. In this paper the operating characteristic for a sampling plan is determined for the case that a lot of products is submitted for inspection with lifetimes spec- ified by an exponentiated log-logistic distribution (ELLD). The

K. Rosaiah; R. R. L. Kantam; Santosh Kumar

2006-01-01

308

Comparative hypsometric analysis of both Earth and Venus topographic distributions  

NASA Astrophysics Data System (ADS)

Previous studies have compared the global topographic distribution of both planets by means of differential hypsometric curves. For the purpose of comparison, the terrestrial oceanic load was removed, and a reference base level was acquired. It was chosen on the basis of geometric considerations and reflected the geometric shape of the mean dynamical equilibrium figure of the planetary surface in both cases. This reference level corresponds to the well-known sea level for the Earth; for Venus, given its slow rate of rotation, a sphere of radius close to the mean, median and modal values of the planetary radii distribution were considered and the radius value of 6051 km arbitrarily taken. These studies were based on the low resolution (100 x 100 sq km) coverage of Venus obtained by the Pioneer Venus altimeter and on the 1 deg x 1 deg terrestrial topography. But, apart from revealing the distinct contrast existing between the Earth's bimodal and Venus' strong unimodal topographic distribution, the choice of such a reference level is inadequate and even misleading for the comparative geophysical understanding of the planetary relief distribution. The present work reinvestigates the comparison between Earth and Venus hypsometric distribution on the basis of the high-resolution data provided, on one hand, by the recent Magellan global topographic coverage of Venus' surface, and on the other hand, by the detailed NCAR 5 x 5 ft. grid topographic database currently available for the Earth's surface.

Rosenblatt, P.; Pinet, P. C.; Thouvenot, E.

1993-03-01

309

CRACK GROWTH ANALYSIS OF SOLID OXIDE FUEL CELL ELECTROLYTES  

SciTech Connect

Defects and Flaws control the structural and functional property of ceramics. In determining the reliability and lifetime of ceramics structures it is very important to quantify the crack growth behavior of the ceramics. In addition, because of the high variability of the strength and the relatively low toughness of ceramics, a statistical design approach is necessary. The statistical nature of the strength of ceramics is currently well recognized, and is usually accounted for by utilizing Weibull or similar statistical distributions. Design tools such as CARES using a combination of strength measurements, stress analysis, and statistics are available and reasonably well developed. These design codes also incorporate material data such as elastic constants as well as flaw distributions and time-dependent properties. The fast fracture reliability for ceramics is often different from their time-dependent reliability. Further confounding the design complexity, the time-dependent reliability varies with the environment/temperature/stress combination. Therefore, it becomes important to be able to accurately determine the behavior of ceramics under simulated application conditions to provide a better prediction of the lifetime and reliability for a given component. In the present study, Yttria stabilized Zirconia (YSZ) of 9.6 mol% Yttria composition was procured in the form of tubes of length 100 mm. The composition is of interest as tubular electrolytes for Solid Oxide Fuel Cells. Rings cut from the tubes were characterized for microstructure, phase stability, mechanical strength (Weibull modulus) and fracture mechanisms. The strength at operating condition of SOFCs (1000 C) decreased to 95 MPa as compared to room temperature strength of 230 MPa. However, the Weibull modulus remains relatively unchanged. Slow crack growth (SCG) parameter, n = 17 evaluated at room temperature in air was representative of well studied brittle materials. Based on the results, further work was planned to evaluate the strength degradation, modulus and failure in more representative environment of the SOFCs.

S. Bandopadhyay; N. Nagabhushana

2003-10-01

310

A fractal approach to dynamic inference and distribution analysis  

PubMed Central

Event-distributions inform scientists about the variability and dispersion of repeated measurements. This dispersion can be understood from a complex systems perspective, and quantified in terms of fractal geometry. The key premise is that a distribution's shape reveals information about the governing dynamics of the system that gave rise to the distribution. Two categories of characteristic dynamics are distinguished: additive systems governed by component-dominant dynamics and multiplicative or interdependent systems governed by interaction-dominant dynamics. A logic by which systems governed by interaction-dominant dynamics are expected to yield mixtures of lognormal and inverse power-law samples is discussed. These mixtures are described by a so-called cocktail model of response times derived from human cognitive performances. The overarching goals of this article are twofold: First, to offer readers an introduction to this theoretical perspective and second, to offer an overview of the related statistical methods.

van Rooij, Marieke M. J. W.; Nash, Bertha A.; Rajaraman, Srinivasan; Holden, John G.

2013-01-01

311

Spatial analysis improves species distribution modelling during range expansion.  

PubMed

Species distribution models (SDMs) assume equilibrium between species' distribution and the environment. However, this assumption can be violated under restricted dispersal and spatially autocorrelated environmental conditions. Here we used a model to simulate species' ranges expansion under two non-equilibrium scenarios, evaluating the performance of SDM coupled with spatial eigenvector mapping. The highest fit is for the models that include space, although the relative importance of spatial variables during the range expansion differs in the two scenarios. Incorporating space to the models was important only under colonization-lag non-equilibrium, under the expected scenario. Thus, mechanisms that generate range cohesion and determine species' distribution under climate changes can be captured by spatial modelling, with advantages compared with other techniques and in line with recent claims that SDMs have to account for more complex dynamic scenarios. PMID:18664417

De Marco, Paulo; Diniz-Filho, José Alexandre Felizola; Bini, Luis Mauricio

2008-10-23

312

Data distribution and analysis: a step to improving nursing quality.  

PubMed

Measurement is a cornerstone for improvement activities, and although the MetroHealth Medical Center in Cleveland, OH, gathered a significant amount of improvement data, it did not have a consistent mechanism for sharing the data with the nursing unit and the frontline nursing staff. A process was implemented to improve data distribution, thus making the data more accessible. Following the implementation of this process, the frontline nurses were more engaged in improvement activities, and significant improvement was noted on several measures. The findings suggest that consistent and meaningful data distribution is an important component in improving the quality of care. PMID:17708330

Amin, Sandra G; Fiorta, Ann; Niesen, Jacquelyn A

313

Evaluation of frequency distributions for flood hazard analysis  

USGS Publications Warehouse

Many different frequency distributions and fitting methods are used to determine the magnitude and frequency of floods and rainfall. Ten different combinations of frequency distributions and fitting methods are evaluated by summarizing the differences in the 0.002 exceedance probability quantile (500-year event), presenting graphical displays of the 10 estimates of the 0.002 quantile, and performing statistical tests to determine if differences are statistically significant. This evaluation indicated there are some statistically significant differences among the methods but, from an engineering standpoint, these differences may not be significant.

Thomas, Jr. , Wilbert, O.; Kuriki, Minoru; Suetsugi, Tadashi

1995-01-01

314

Phylogenetic analysis reveals wide distribution of globin X  

PubMed Central

The vertebrate globin gene repertoire consists of seven members that differ in terms of structure, function and phyletic distribution. While hemoglobin, myoglobin, cytoglobin, and neuroglobin are present in almost all gnathostomes examined so far, other globin genes, like globin X, are much more restricted in their phyletic distribution. Till today, globin X has only been found in teleost fish and Xenopus. Here, we report that globin X is also present in the genomes of the sea lamprey, ghost shark and reptiles. Moreover, the identification of orthologs of globin X in crustacean, insects, platyhelminthes, and hemichordates confirms its ancient origin.

2011-01-01

315

Distribution  

Microsoft Academic Search

e're closer than you think: Portland's geographic location and Oregon's transportation infra - structure offer unmatched con - nectivity and time savings to international and domestic markets. Our economic development practices combine project-ready property with efficient, high-capacity infrastructure to create today's logistics advantages. Connecting people, places and products is the core of Portland's distribution and logistics industry sec - tor.

F. Gregory; B. Boyd; R. Bridges; D. Mitchell; J. Halsell; S. Fancher; D. King; R. Fore; E. Mango; D. Berlinrut; M. Leinbach; M. Maier; M. Wetmore; H. Herring; J. Guidi; M. Coolidge; J. Heald; T. Knox; D. Bartine; R. Bailey; H. Delgado; P. Conant; J. Madura; R. Thomas; F. Merceret; G. Allen; E. Bensman; R. Dittemore; N. Feldman; C. Boykin; H. Tileston; F. Brody; L. Hagerman; S. Pearson; L. Uccellini; W. Vaughan; J. Golden; D. Johnson; J. McQueen; B. Roberts; L. Freeman; G. Jasper; B. Hagemeyer; A. McCool; X. W. Proenza; S. Glover

2006-01-01

316

The Aggregation of Individual Distributive Preferences through the Distributive Liberal Social Contract : Normative Analysis  

Microsoft Academic Search

We consider abstract social systems of private property, made of n individuals endowed with non-paternalistic interdependent preferences, who interact through exchanges on competitive markets and Pareto-efficient lumpsum transfers. The transfers follow from a distributive liberal social contract defined as a redistribution of initial endowments such that the resulting market equilibrium allocation is both Pareto-efficient relative to individual interdependent preferences, and

Jean Mercier-Ythier

2010-01-01

317

Social Distribution, Ghettoization, and Educational Triage: A Marxist Analysis.  

ERIC Educational Resources Information Center

|Discusses how many urban students are written off as unworthy of scant educational resources, using Weber and Marx to discuss how educational triage is best understood theoretically, exploring how broader processes of social distribution and triage link up with daily practices and policies in urban classrooms, and highlighting the need for a…

Cameron, Jeanne

2000-01-01

318

ANFIS Based Credit Analysis for Distribution Management System  

Microsoft Academic Search

Reclaim of electricity fee, which is ordinarily called as receivables in distribution management system, is very important for public utility, especially in the circumstance of electricity market, and to predict which credit types the clients would be is one of the most important work. Based on the data of MIS and objection of credit management, a practical credit index is

Hui Zhou; Yi Wang; Wei Wang; Tao Li; Hong Yang

2009-01-01

319

Effective-index matrix analysis of distributed feedback semiconductor lasers  

Microsoft Academic Search

A method is developed for calculating the threshold gain in distributed feedback (DFB) semiconductor lasers consisting of a four-layer waveguide. Each corrugation region is expressed by a transfer matrix comprising the complex effective index, and the threshold calculation is reduced to the matrix multiplication. It is found that a periodic variation of the effective gain and loss induced by the

Toshihiko Makino

1992-01-01

320

Continuous, online monitoring and analysis in large water distribution networks  

Microsoft Academic Search

Clean drinking water and safe water supply is vital to our life. Recent advances in technologies have made it possible to deploy smart sensor networks in large water distribution networks to monitor and identify the water quality online. In such a large-scale real-time monitoring application, large amounts of data stream out of multiple concurrent sensors continuously. In this paper, we

Xiuli Ma; Hongmei Xiao; Shuiyuan Xie; Qiong Li; Qiong Luo; Chunhua Tian

2011-01-01

321

Distributed simulation for power system analysis including shipboard systems  

Microsoft Academic Search

Power systems are distributed in nature. Often they can be divided into sections or groups and treated separately. Terrestrial power systems are divided into separate utilities and are controlled by different regional transmission organization (RTO). Each RTO has detailed data for the area under its control, but only limited data and boundary measurements of the external network. Additionally, shipboard power

Jian Wu; Noel N. Schulz; Wenzhong Gao

2007-01-01

322

Optimizing Distributed Practice: Theoretical Analysis and Practical Implications  

Microsoft Academic Search

More than a century of research shows that increasing the gap between study episodes using the same material can enhance retention, yet little is known about how this so-called distributed practice effect unfolds over nontrivial periods. In two three-session laboratory studies, we examined the effects of gap on retention of foreign vocabulary, facts, and names of visual objects, with test

Nicholas J. Cepeda; Noriko Coburn; Doug Rohrer; John T. Wixted; Michael C. Mozer; Harold Pashler

2009-01-01

323

Fractal analysis of foliage distribution in loblolly pine crowns  

Microsoft Academic Search

A new method for estimating fractal characteristics (fractal dimension and foliage density) of a single crown or its portions is developed. The proposed method operates with volume and mass of natural units of the crown, such as shoots and branches, rather than with numbers of regular cubes. Fractal dimension alone is not sufficient to describe foliage distribution in the crown

Boris Zeide

1998-01-01

324

THE EPANET PROGRAMMER'S TOOLKIT FOR ANALYSIS OF WATER DISTRIBUTION SYSTEMS  

EPA Science Inventory

The EPANET Programmer's Toolkit is a collection of functions that helps simplify computer programming of water distribution network analyses. the functions can be used to read in a pipe network description file, modify selected component properties, run multiple hydraulic and wa...

325

RAINFALL DATA ANALYSIS USING THE GAMMA DISTRIBUTION FUNCTION  

EPA Science Inventory

The Gamma distribution function can be useful for fitting rainfall data. n integral part of the assessment of storm loads on water quality is the statistical evaluation of rainfall records. ourly rainfall records of many years duration are cumbersome and difficult to analyze. he ...

326

Number and distribution of lymphocytes in man. A critical analysis  

Microsoft Academic Search

Summary The number and distribution of lymphocytes in man has not yet been determined quantitatively. But there is limited information available on the cell number or the size of single compartments of the human lymphoid cell system. The problem is to derive knowledge about the quantitatively unknown compartments from other data. This is done by extrapolation of data on rats

F. Trepel

1974-01-01

327

A novel technique for the analysis of radial distribution systems  

Microsoft Academic Search

This paper presents a novel technique to obtain the solution of load flow in radially operated distribution networks, in which the loads can be represented by any model. This method is simple, easy to program and is based on the formation of a constant sparse upper triangular matrix, which is used to determine the bus voltages. Test results of IEEE

P. Aravindhababu; S. Ganapathy; K. R. Nayar

2001-01-01

328

An Analysis of U.S. Rice Distribution Patterns.  

National Technical Information Service (NTIS)

A survey of U.S. rice distribution patterns between marketing years 1955/56 and 1974/75 indicates that brewers and breakfast cereal manufacturers became increasingly important outlets in the domestic market. Exports, however, overtook domestic use and inc...

S. H. Holder A. Smith

1978-01-01

329

An analysis of update ordering in distributed replication systems  

Microsoft Academic Search

This paper analyses update ordering and its impact on the performance of a distributed replication system. We propose a model for update orderings and constraints and develop a number of algorithms for implementing different ordering constraints. A performance study is then carried out to analyse the update-ordering model. We show that our model allows the definition of an ordering constraint

Wanlei Zhou; Li Wang; Weijia Jia

2004-01-01

330

Mechanical Network in Titin Immunoglobulin from Force Distribution Analysis  

Microsoft Academic Search

The role of mechanical force in cellular processes is increasingly revealed by single molecule experiments and simulations of force-induced transitions in proteins. How the applied force propagates within proteins determines their mechanical behavior yet remains largely unknown. We present a new method based on molecular dynamics simulations to disclose the distribution of strain in protein structures, here for the newly

Wolfram Stacklies; M. Cristina Vega; Matthias Wilmanns; Frauke Gräter

2009-01-01

331

Comparison of ceramic material effects on the flexural Weibull statistics and fracture of high volume fraction particle reinforced aluminum  

Microsoft Academic Search

The effects of the ceramic particle material on the flexural Weibull modulus, characteristic flexural strength, and damage parameters of particulate-reinforced metal-matrix composites were studied. Three high volume fill composites were fabricated using the pressure infusion casting technique: they were reinforced with SiC, B4C, and ?-Al2O3 particles. Four-point bend testing determined the effects of particle material on flexural strength and elastic

Walter L. Prater

2006-01-01

332

An engineering methodology to assess effects of weld strength mismatch on cleavage fracture toughness using the Weibull stress approach  

Microsoft Academic Search

This work describes the development of an engineering approach based upon a toughness scaling methodology incorporating the\\u000a effects of weld strength mismatch on crack-tip driving forces. The approach adopts a nondimensional Weibull stress, $${\\\\bar{{\\\\sigma}}_w}$$, as a the near-tip driving force to correlate cleavage fracture across cracked weld configurations with different mismatch\\u000a conditions even though the loading parameter (measured by J)

Claudio Ruggieri

2010-01-01

333

Buckling Analysis of Wind Turbine Blade Using Pressure Distributions Obtained from CFD  

Microsoft Academic Search

Buckling analysis of a rotating wind turbine blade using FEM(finite element method) is presented here. This study is distinct from its counterparts in adopting the pressure distributions obtained from CFD(computational fluid dynamics) calculations to perform the buckling analysis. A code is developed to feed those pressure distributions into the FE(finite element) model of the blade. Through the analysis, load factors

Wei Liu; Yuli Ma; Xianyue Su; Kefu Huang

2009-01-01

334

Groundwork for Integrated Analysis of Distributed S3C Data  

Microsoft Academic Search

We present a vision for the evolution of existing and future NASA Sun Solar System Connection (S3C) data resources into an integrated data analysis environment. Focusing first on the time-series datasets typical of in- situ measurements, we describe an architecture designed to overcome the traditional barriers to integrated analysis, namely data access and format variations. We are building a groundwork

J. Vandegriff; A. Roberts; A. Szabo

2006-01-01

335

Nonlinear structural analysis on distributed-memory computers  

NASA Astrophysics Data System (ADS)

A computational strategy is presented for the nonlinear static and postbuckling analyses of large complex structures on massively parallel computers. The strategy is designed for distributed-memory, message-passing parallel computer systems. The key elements of the proposed strategy are: (1) a multiple-parameter reduced basis technique; (2) a nested dissection (or multilevel substructuring) ordering scheme; (3) parallel assembly of global matrices; and (4) a parallel sparse equation solver. The effectiveness of the strategy is assessed by applying it to thermo-mechanical postbuckling analyses of stiffened composite panels with cutouts, and nonlinear large-deflection analyses of HSCT models on Intel Paragon XP/S computers. The numerical studies presented demonstrate the advantages of nested dissection-based solvers over traditional skyline-based solvers on distributed memory machines.

Watson, Brian C.; Noor, Ahmed K.

1995-04-01

336

Relaxation of Terrace-width Distributions: Novel Analysis and Features  

NASA Astrophysics Data System (ADS)

We describe a Fokker-Planck scheme to describe the relaxation of the terrace-width distribution (TWD) on a vicinal surface toward the generalized Wigner form describing equilibrium.ootnotetextA. BH. Hamouda, A. Pimpinelli, & TLE, Surface Sci. 602 (2008) 3569 We performed KMC calculations on the standard minimal SOS model to show that the time constant gives physical information, in particular the energy barrier of the rate-determining process. For close-packed steps, this involves kink-antikink generation, breaking 3 rather than the expected 2 lateral bonds (the latter associated with equilibrium fluctuations). We discuss strengths and limitations of this FP procedure, higher moments of the distribution beyond the variance, and generalizations to other step orientations.

Einstein, T. L.; Hamouda, Ajmi Bh.; Pimpinelli, A.

2009-03-01

337

A Distributed Datacube Analysis Service for Radio Telescopes  

NASA Astrophysics Data System (ADS)

Current- and next-generation radio telescopes are poised to produce data at an unprecedented rate. We are developing the cyberinfrastructure to enable distributed processing and storage of FITS data cubes from these telescopes. In this contribution, we will present the data storage and network infrastructure that enables efficient searching, extraction and transfer of FITS datacubes. The infrastructure combines the iRODS distributed data management with a custom spatially-enabled PostgreSQL database. The data management system ingests FITS cubes, automatically populating the metadata database using FITS header data. Queries to the metadata service return matching records using VOTable format. The iRODS system allows for a distributed network of fileservers to store large data sets redundantly with a minimum of upkeep. Transfers between iRODS data sites use parallel I/O streams for maximum speed. Files are staged to the optimal host for download by an end user. The service can automatically extract subregions of individual or adjacent cubes registered to user-defined astrometric grids using the Montage package. The data system can query multiple surveys and return spatially registered data cubes to the user. Future development will allow the data system to utilize distributed processing environment to analyze datasets, returning only the calculation results to the end user. This cyberinfrastructure project combines many existing, open-source packages into a single deployment of a data system. The codebase can also function on two-dimensional images. The project is funded by CANARIE under the Network-Enabled Platforms 2 program.

Mahadevan, V.; Rosolowsky, E.

2011-07-01

338

Completion report harmonic analysis of electrical distribution systems  

Microsoft Academic Search

Harmonic currents have increased dramatically in electrical distribution systems in the last few years due to the growth in non-linear loads found in most electronic devices. Because electrical systems have been designed for linear voltage and current waveforms; (i.e. nearly sinusoidal), non-linear loads can cause serious problems such as overheating conductors or transformers, capacitor failures, inadvertent circuit breaker tripping, or

Tolbert

1996-01-01

339

Applying Bayesian network to distribution system reliability analysis  

Microsoft Academic Search

This paper proposes a Bayesian network (BN) model for distribution-system-reliability assessment and reassessment. The zone-based FMEA technique is applied to construct the BN model. During forward propagation of probabilistic information, load-point and system reliability indices are calculated. And the weak points are identified during backward propagation for what-if studies. A dual isomorphic model is used to obtain outage probabilistic indices

Wang Chengshan; Xie Yinghua

2004-01-01

340

Analysis of a collaborative workflow process with distributed actors  

Microsoft Academic Search

Current worko w management technology oers rich sup- port for process-oriented coordination of distributed teamwork. In this paper, we evaluate the performance of an industrial worko w process where similar tasks can be performed by various actors at many dier- ent locations. We analyzed a large worko w process log with state-of-the art mining tools associated with the ProM framework.

Hajo A. Reijers; Minseok Song; Byungduk Jeong

2009-01-01

341

An Automated Analysis of the Security of Quantum Key Distribution  

Microsoft Academic Search

This paper discusses the use of computer-aided verification as a practical means for analysing quantum information systems; specifically, the BB84 protocol for quantum key distribution is examined using this method. This protocol has been shown to be unconditionally secure against all attacks in an information-theoretic setting, but the relevant security proof requires a thorough understanding of the formalism of quantum

Rajagopal Nagarajan; Nikolaos Papanikolaou; Garry Bowen; Simon J. Gay

2005-01-01

342

Diffractive parton distributions from the analysis with higher twist  

SciTech Connect

Diffractive parton distributions of the proton are determined from fits to diffractive data from HERA. In addition to the twist-2 contribution, the twist-4 contribution from longitudinally polarized virtual photons is considered, which is important in the region of small diffractive masses. A new prediction for the longitudinal diffractive structure function is presented which differs significantly from that obtained in the pure twist-2 analyses.

Golec-Biernat, Krzysztof [Institute of Nuclear Physics Polish Academy of Sciences, Cracow (Poland); Institute of Physics, University of Rzeszow, Rzeszow (Poland); Luszczak, Agnieszka [Institute of Nuclear Physics Polish Academy of Sciences, Cracow (Poland)

2007-12-01

343

MammoGrid: Large-Scale Distributed Mammogram Analysis  

Microsoft Academic Search

Breast cancer as a medical condition and mammograms as images exhibit many\\u000adimensions of variability across the population. Similarly, the way diagnostic\\u000asystems are used and maintained by clinicians varies between imaging centres\\u000aand breast screening programmes, and so does the appearance of the mammograms\\u000agenerated. A distributed database that reflects the spread of pathologies\\u000aacross the population is an

S. Roberto Amendolia; Michael Brady; Richard McClatchey; Miguel Mulet-Parada; Mohammed Odeh; Tony Solomonides

2004-01-01

344

Agent-based reasoning for distributed multi-INT analysis  

NASA Astrophysics Data System (ADS)

Fully exploiting the intelligence community's exponentially growing data resources will require computational approaches differing radically from those currently available. Intelligence data is massive, distributed, and heterogeneous. Conventional approaches requiring highly structured and centralized data will not meet this challenge. We report on a new approach, Agent-Based Reasoning (ABR). In NIST evaluations, the use of ABR software tripled analysts' solution speed, doubled accuracy, and halved perceived difficulty. ABR makes use of populations of fine-grained, locally interacting agents that collectively reason about intelligence scenarios in a self-organizing, "bottom-up" process akin to those found in biological and other complex systems. Reproduction rules allow agents to make inferences from multi-INT data, while movement rules organize information and optimize reasoning. Complementary deterministic and stochastic agent behaviors enhance reasoning power and flexibility. Agent interaction via small-world networks - such as are found in nervous systems, social networks, and power distribution grids - dramatically increases the rate of discovering intelligence fragments that usefully connect to yield new inferences. Small-world networks also support the distributed processing necessary to address intelligence community data challenges. In addition, we have found that ABR pre-processing can boost the performance of commercial text clustering software. Finally, we have demonstrated interoperability with Knowledge Engineering systems and seen that reasoning across diverse data sources can be a rich source of inferences.

Inchiosa, Mario E.; Parker, Miles T.; Perline, Richard

2006-06-01

345

Discovering Statistical Models of Availability in Large Distributed Systems: An Empirical Study of SETI@home  

Microsoft Academic Search

In the age of cloud, Grid, P2P, and volunteer distributed computing, large-scale systems with tens of thousands of unreliable hosts are increasingly common. Invariably, these systems are composed of heterogeneous hosts whose individual availability often exhibit different statistical properties (for example stationary versus nonstationary behavior) and fit different models (for example exponential, Weibull, or Pareto probability distributions). In this paper,

Bahman Javadi; Derrick Kondo; Jean-Marc Vincent; David P. Anderson

2011-01-01

346

ASYMMETRIC ASPERITY HEIGHT DISTRIBUTIONS IN A SCALE-DEPENDENT MODEL FOR CONTACT AND FRICTION  

Microsoft Academic Search

The effect of an asymmetric distribution of asperity heights is accounted for in a recently developed scale-dependent multi- asperity model of contact and friction. A Weibull distribution of asperity heights is used which allows the skew and kurtosis to be varied, but not independently of each other. The contact and friction model used includes the effects of adhesion and of

George G. Adams; Sinan Müftü

2003-01-01

347

Current Issues and Challenges in Global Analysis of Parton Distributions  

NASA Astrophysics Data System (ADS)

A new implementation of precise perturbative QCD calculation of deep inelastic scattering structure functions and cross sections, incorporating heavy quark mass effects, is applied to the global analysis of the full HERA I data sets on NC and CC cross sections, in conjunction with other experiments. Improved agreement between the NLO QCD theory and the global data sets are obtained. Comparison of the new results to that of previous analysis based on conventional zero-mass parton formalism is made. Exploratory work on implications of new fixed-target neutrino scattering and Drell-Yan data on global analysis is also discussed.

Tung, Wu-Ki

2007-01-01

348

Global Uncertainty and Sensitivity Analysis of Spatially Distributed Hydrological Model, Regional Simulation Model (RSM), to spatially distributed factors  

NASA Astrophysics Data System (ADS)

This research addresses two aspects of spatially distributed modeling: uncertainty analysis (UA), described as propagation of uncertainty from spatially distributed input factors on model outputs; and sensitivity analysis (SA) defined as assessment of relative importance of spatially distributed factors on the model output variance. An evaluation framework for spatially distributed models is proposed based on a combination of sequential Gaussian simulation (sGs) and the global, variance-based, SA method of Sobol to quantify model output uncertainty due to spatially distributed input factors, together with the corresponding sensitivity measures. The framework is independent of model assumptions; it explores the whole space of input factors, provides measures of factor’s importance (first-order effects) and their interactions (higher-order effects), and assesses the effect of spatial resolution of the model input factors, one of the least understood contributors to uncertainty and sensitivity of distributed models. A spatially distributed hydrological model (Regional Simulation Model, RSM), applied to a site in South Florida (Water Conservation Area-2A), is used as a benchmark for the study. The model domain is spatially represented by triangular elements (average size of 1.1 km2). High resolution land elevation measurements (400 x 400 m, +/-0.15 m vertical error) obtained by the USGS' Airborne Height Finder survey are used in the study. The original survey data (approximately 2,600 points) together with smaller density subsets drawn from this data (1/2, 1/4, 1/8, 1/16, 1/32 of original density) are used for generating equiprobable maps of effective land elevation factor values via sGs. These alternative realizations are sampled pseudo-randomly and used as inputs for model runs. In this way, uncertainty regarding a spatial representation of the elevation surface is transferred into uncertainty of model outputs. The results show that below a specific threshold of data density (1/8), model uncertainty and sensitivity are impacted by the density of land elevation data used for deriving effective land elevation factor values. Below the threshold of data density, uncertainty of model outputs is observed to increase with a decrease of density of elevation data. Similar pattern is observed for the relative importance of sensitivity indexes of the land elevation factor. The results indicate that reduced data density of land elevation could be used without significantly compromising the certainty of RSM predictions and the subsequent decision making process for the specific WCA-2A conditions. The methodology proposed in this research is useful for a model quality control and for guiding field measurement campaigns by optimizing data collection in terms of cost-benefit analysis.

Zajac, Z. B.; Munoz-Carpena, R.; Vanderlinden, K.

2009-12-01

349

Analysis of distributed control systems with shared communication and computation resources  

Microsoft Academic Search

We address the analysis and implementation of a distributed control system on a network of communicating control units, resulting in a networked control system (NCS). We propose an approach based on three steps: control system analysis in terms of sampling times and delays, mapping of control loops to computation\\/communication hardware components, and scheduling analysis. This procedure is especially important for

Payam Naghshtabrizi; Joao P. Hespanha

2009-01-01

350

Probability distributions of land surface wind speeds over North America  

Microsoft Academic Search

Knowledge of the probability distributions of surface wind speeds (SWS) is essential for surface flux estimation, wind power estimation, and wind risk assessments. The two-parameter Weibull distribution is the most widely used empirical distribution for SWS. This study considers the probability density function (PDF) of 3-hourly observations from 720 weather stations over North America for the period 1979-1999. The PDF

Yanping He; Adam Hugh Monahan; Colin G. Jones; Aiguo Dai; Sebastien Biner; Daniel Caya; Katja Winger

2010-01-01

351

Probability distributions of land surface wind speeds over North America  

Microsoft Academic Search

Knowledge of the probability distributions of surface wind speeds (SWS) is essential for surface flux estimation, wind power estimation, and wind risk assessments. The two-parameter Weibull distribution is the most widely used empirical distribution for SWS. This study considers the probability density function (PDF) of 3-hourly observations from 720 weather stations over North America for the period 1979–1999. The PDF

Yanping He; Adam Hugh Monahan; Colin G. Jones; Aiguo Dai; Sebastien Biner; Daniel Caya; Katja Winger

2010-01-01

352

Flow microfluorometric analysis of sperm DNA content: effect of cell shape on the fluorescence distribution  

Microsoft Academic Search

The DNA content of individual sperm from populations of acriflavine-stained cells was investigated by analysis of fluorescence frequency distributions obtained with high-resolution flow-systems instruments. Sperm with spherical or cylindrical heads from three mollusk species produce narrow, symmetric fluorescence distributions. Flat sperm heads from six eutherian species produce asymmetric distributions consisting of a peak with a lateral extension to higher fluorescence

Barton L. Gledhill; Suzanne Lake; Lloyd L. Steinmetz; Joe W. Gray; James R. Crawford; Phillip N. Dean; Marvin A. Van Dilla

1976-01-01

353

On the accuracy of fragment size measurement by image analysis in combination with some distribution functions  

Microsoft Academic Search

Summary  Size distributions of fragments of crushed rock in conveyor belts and of blasted rock in a muckpile obtained by sieving are\\u000a compared with the size distributions obtained by digital image analysis of photographs of the same materials taken on-site.\\u000a Several calculation methods are tested, based on the raw distribution of fragment areas and on the volume-transformed ones.\\u000a The influence of

J. A. Sanchidrián; P. Segarra; F. Ouchterlony; L. M. López

2009-01-01

354

Sources\\/sinks analysis with satellite sensing for exploring global atmospheric CO2 distributions  

Microsoft Academic Search

There is growing interest in CO2 budget analysis since space-borne measurements of global CO2 distribution have been conducted (e.g, GOSAT project). Here we simulated the global CO2 distribution to estimate individual source\\/sink contributions. The chemical transport model (GEOS-Chem) was used in order to simulate the global CO2 distribution with updated global sources\\/sinks with 2°x2.5° horizontal resolution. In addition, 3-D emissions

C. Shim; R. Nassar; J. Kim

2010-01-01

355

Structure-function analysis and psi, jet, W, and Z production: Determining the gluon distribution  

Microsoft Academic Search

We perform a next-to-leading-order structure-function analysis of deep-inelastic ..mu..N and ..nu..N scattering data and find acceptable fits for a range of input gluon distributions. We show three equally acceptable sets of parton distributions which correspond to gluon distributions which are (1) ''soft,'' (2) ''hard,'' and (3) which behave as xG(x)approx.1\\/ ..sqrt..x at small x. J\\/psi and prompt photon hadroproduction data

A. D. Martin; R. G. Roberts; W. J. Stirling

1988-01-01

356

Analysis of an algorithm for distributed recognition and accountability  

SciTech Connect

Computer and network systems are available to attacks. Abandoning the existing huge infrastructure of possibly-insecure computer and network systems is impossible, and replacing them by totally secure systems may not be feasible or cost effective. A common element in many attacks is that a single user will often attempt to intrude upon multiple resources throughout a network. Detecting the attack can become significantly easier by compiling and integrating evidence of such intrusion attempts across the network rather than attempting to assess the situation from the vantage point of only a single host. To solve this problem, we suggest an approach for distributed recognition and accountability (DRA), which consists of algorithms which ``process,`` at a central location, distributed and asynchronous ``reports`` generated by computers (or a subset thereof) throughout the network. Our highest-priority objectives are to observe ways by which an individual moves around in a network of computers, including changing user names to possibly hide his/her true identity, and to associate all activities of multiple instance of the same individual to the same network-wide user. We present the DRA algorithm and a sketch of its proof under an initial set of simplifying albeit realistic assumptions. Later, we relax these assumptions to accommodate pragmatic aspects such as missing or delayed ``reports,`` clock slew, tampered ``reports,`` etc. We believe that such algorithms will have widespread applications in the future, particularly in intrusion-detection system.

Ko, C.; Frincke, D.A.; Goan, T. Jr.; Heberlein, L.T.; Levitt, K.; Mukherjee, B.; Wee, C. [California Univ., Davis, CA (United States). Dept. of Computer Science

1993-08-01

357

Single Cell Analysis of Drug Distribution by Intravital Imaging  

PubMed Central

Recent advances in the field of intravital imaging have for the first time allowed us to conduct pharmacokinetic and pharmacodynamic studies at the single cell level in live animal models. Due to these advances, there is now a critical need for automated analysis of pharmacokinetic data. To address this, we began by surveying common thresholding methods to determine which would be most appropriate for identifying fluorescently labeled drugs in intravital imaging. We then developed a segmentation algorithm that allows semi-automated analysis of pharmacokinetic data at the single cell level. Ultimately, we were able to show that drug concentrations can indeed be extracted from serial intravital imaging in an automated fashion. We believe that the application of this algorithm will be of value to the analysis of intravital microscopy imaging particularly when imaging drug action at the single cell level.

Giedt, Randy J.; Koch, Peter D.; Weissleder, Ralph

2013-01-01

358

Comparative analysis between synchronous and induction machines for distributed generation applications  

Microsoft Academic Search

This paper presents a detailed comparative analysis between synchronous and induction machines for distributed generation applications. The impacts of these generators on the distribution network performance are determined and compared by using computational simulations. The technical factors analyzed are steady-state voltage profile, electrical power losses, voltage stability, transient stability, voltage sags during unbalanced faults, and short-circuit currents. The results showed

Walmir Freitas; Jose C. M. Vieira; Andre Morelato; Luiz C. P. da Silva; Vivaldo F. da Costa; Flavio A. B. Lemos

2006-01-01

359

A particle size distribution analysis of stressed HPLC column packing material  

Microsoft Academic Search

A particle size distribution analysis has been completed on three different HPLC column packing materials including silica gel (Si60) and two bonded phases (RP8 and RP18). The stationary phases were subjected to 18 hours stress with 1 N or 3 N KOH and found to have quantitatively different distribution patterns initially, at 13 hours and finally at 18 hours although

T. D. Wilson; D. M. Simmons

1991-01-01

360

A particle size distribution analysis of used HPLC column packing material  

Microsoft Academic Search

Particle size distribution analysis and scanning electron microscopy (SEM) were carried out on eight used HPLC columns containing either irregular silica based, spherical silica based or spherical polymer based packing material. Particle size distributions of the used irregular silica based columns were at least bimodat at the outlet ends and either biomodal or log-normal at the inlet ends with regular

T. D. Wilson; D. M. Simmons

1993-01-01

361

The Distribution of Use of Library Materials: Analysis of Data from the University of Pittsburgh.  

ERIC Educational Resources Information Center

|Evaluates the validity of using circulation data as the index to the total utilization of a library collection and tests the hypothesis that the proposed mixture of Poisson distributions can describe and predict various use distribution. Seven statistical analysis listings, six algorithms, 20 tables, and 43 references are provided. (Author/RBF)|

Hayes, Robert M.

1981-01-01

362

Multiplatform and multi-technology system for interpretation and analysis of protection tripping in distribution substations  

Microsoft Academic Search

This paper describes the research and development results of a multi-technology and multi-platform system for the interpretation and analysis of the protection tripping in distribution substations. As part of the project it was developed a system for the analytical interpretation of the protection in order to generate tripping diagnosis of protection relays in power distribution substations. The system was designed

F. Crispino; L. C. Magrini; L. Ogiboski; S. Nicoli; N. J. Salles; E. D. C. Delvecchi; R. O. Milanese

2010-01-01

363

Industry sector analysis, Indonesia: Electric power distribution equipment. Export trade information  

SciTech Connect

The market survey covers the electric power distribution equipment market in Indonesia. The analysis contains statistical and narrative information on projected market demand, end-users; receptivity of Indonesian consumers to U.S. products; the competitive situation, and market access (tariffs, non-tariff barriers, standards, taxes, distribution channels). It also contains key contact information.

Sihombing, P.

1991-08-20

364

Industry sector analysis Mexico: Electric power distribution equipment. Export trade information  

SciTech Connect

The market survey covers the electric power distribution equipment market in Mexico. The analysis contains statistical and narrative information on projected market demand, end-users; receptivity of Mexican consumers to U.S. products; the competitive situation, and market access (tariffs, non-tariff barriers, standards, taxes, distribution channels). It also contains key contact information.

Not Available

1991-08-01

365

Development of Distribution System Reliability and Risk Analysis Models. Final Report.  

National Technical Information Service (NTIS)

This report describes work completed in fulfillment of EPRI Research Project 1356-1, Develop Distribution System Reliability and Risk Analysis Model. This volume comprises the background material needed to determine the state-of-the-art in reliability ass...

J. E. D. Northcote-Green R. Billinton T. D. Vismor

1981-01-01

366

System Analysis for the Huntsville Operation Support Center, Distributed Computer System.  

National Technical Information Service (NTIS)

HOSC as a distributed computing system, is responsible for data acquisition and analysis during Space Shuttle operations. HOSC also provides computing services for Marshall Space Flight Center's nonmission activities. As mission and nonmission activities ...

F. M. Ingels D. Massey

1985-01-01

367

System Analysis for the Huntsville Operational Support Center Distributed Computer System.  

National Technical Information Service (NTIS)

The Huntsville Operations Support Center (HOSC) is a distributed computer system used to provide real time data acquisition, analysis and display during NASA space missions and to perform simulation and study activities during non-mission times. The prima...

F. M. Ingels J. Mauldin

1984-01-01

368

An Analysis of Distributed Lag in Feedback Control Systems with General Impedance Termination.  

National Technical Information Service (NTIS)

Analytical methods of analysis for linear feedback control systems are extended to include distributed lag in its most generalized form (terminating impedance having both resistive and reactive components). Methods are developed for examining analytically...

E. W. Ivy

1965-01-01

369

On the Probability and Spatial Distribution of Ocean Surface Currents  

NASA Astrophysics Data System (ADS)

Insights into the probability distribution of ocean currents are important for various applications such as the chance to encounter extreme events, which may affect, for example, marine construction, and for estimating the energy that can be extracted from the ocean. In addition, for devising better parameterizations for submesoscale mixing, which present climate models cannot resolve, one should understand the velocity distribution and its relation to the various forcing of surface ocean circulation. Here, the authors investigate the probability distribution of surface currents from the Gulf of Eilat/Aqaba measured by high-frequency radar. Their results show that the distribution of ocean current speeds can be approximated by a Weibull distribution. Moreover, the authors demonstrate the existence of spatial variations of the scale and shape parameters of the Weibull distribution over a relatively small region of only a few kilometers. They use a simple surface Ekman layer model to investigate this spatial variability. They find that, when forced by local winds, this model does not reproduce the observations. The addition of Gaussian noise to the zonal and meridional components of the bottom geostrophic currents has only a slight effect on the surface current distribution. However, noise added to the components of the local wind (mimicking wind gusts) has a much greater effect on the distribution of surface currents, suggesting that wind spatial and temporal variability underlay the observed spatial variability of the parameters of the Weibull distribution.

Ashkenazy, Y.; Gildor, H.

2012-04-01

370

Lognormal Distribution of Cellular Uptake of Radioactivity: Statistical Analysis of ?-Particle Track Autoradiography  

PubMed Central

Recently, the distribution of radioactivity among a population of cells labeled with 210Po was shown to be well described by a log-normal (LN) distribution function (J Nucl Med. 2006;47:1049–1058) with the aid of autoradiography. To ascertain the influence of Poisson statistics on the interpretation of the autoradiographic data, the present work reports on a detailed statistical analysis of these earlier data. Methods The measured distributions of ?-particle tracks per cell were subjected to statistical tests with Poisson, LN, and Poisson-lognormal (P-LN) models. Results The LN distribution function best describes the distribution of radioactivity among cell populations exposed to 0.52 and 3.8 kBq/mL of 210Po-citrate. When cells were exposed to 67 kBq/mL, the P-LN distribution function gave a better fit; however, the underlying activity distribution remained log-normal. Conclusion The present analysis generally provides further support for the use of LN distributions to describe the cellular uptake of radioactivity. Care should be exercised when analyzing autoradiographic data on activity distributions to ensure that Poisson processes do not distort the underlying LN distribution.

Neti, Prasad V.S.V.; Howell, Roger W.

2010-01-01

371

Optimizing distributed practice: theoretical analysis and practical implications.  

PubMed

More than a century of research shows that increasing the gap between study episodes using the same material can enhance retention, yet little is known about how this so-called distributed practice effect unfolds over nontrivial periods. In two three-session laboratory studies, we examined the effects of gap on retention of foreign vocabulary, facts, and names of visual objects, with test delays up to 6 months. An optimal gap improved final recall by up to 150%. Both studies demonstrated nonmonotonic gap effects: Increases in gap caused test accuracy to initially sharply increase and then gradually decline. These results provide new constraints on theories of spacing and confirm the importance of cumulative reviews to promote retention over meaningful time periods. PMID:19439395

Cepeda, Nicholas J; Coburn, Noriko; Rohrer, Doug; Wixted, John T; Mozer, Michael C; Pashler, Harold

2009-01-01

372

Completion report harmonic analysis of electrical distribution systems  

SciTech Connect

Harmonic currents have increased dramatically in electrical distribution systems in the last few years due to the growth in non-linear loads found in most electronic devices. Because electrical systems have been designed for linear voltage and current waveforms; (i.e. nearly sinusoidal), non-linear loads can cause serious problems such as overheating conductors or transformers, capacitor failures, inadvertent circuit breaker tripping, or malfunction of electronic equipment. The U.S. Army Center for Public Works has proposed a study to determine what devices are best for reducing or eliminating the effects of harmonics on power systems typical of those existing in their Command, Control, Communication and Intelligence (C3I) sites.

Tolbert, L.M.

1996-03-01

373

MammoGrid: large-scale distributed mammogram analysis.  

PubMed

Breast cancer as a medical condition and mammograms as images exhibit many dimensions of variability across the population. Similarly, the way diagnostic systems are used and maintained by clinicians varies between imaging centres and breast screening programmes, and so does the appearance of the mammograms generated. A distributed database that reflects the spread of pathologies across the population is an invaluable tool for the epidemiologist and the understanding of the variation in image acquisition protocols is essential to a radiologist in a screening programme. Exploiting emerging grid technology, the aim of the MammoGrid [1] project is to develop a Europe-wide database of mammograms that will be used to investigate a set of important healthcare applications and to explore the potential of the grid to support effective co-working between healthcare professionals. PMID:14663986

Amendolia, S Roberto; Brady, Michael; McClatchey, Richard; Mulet-Parada, Miguel; Odeh, Mohammed; Solomonides, Tony

2003-01-01

374

Circuit level Alternating-Direction-Implicit approach to transient analysis of power distribution networks  

Microsoft Academic Search

This paper presents an efficient method for transient analysis of power distribution networks. We employ an iterative approach-Alternating-Direction-Implicit (ADI) method-to solving the circuit matrices of power distribution networks. In contrast to the existing finite-difference based ADI approach to power\\/ground grid analysis, where transmission-line was used to model the mesh-structured P\\/G grids (TLM-ADI), we apply ADI scheme to directly solve P\\/G

Weikun Guo; S. X.-D. Tan

2003-01-01

375

Electron density distribution in Si and Ge using multipole, maximum entropy method and pair distribution function analysis  

NASA Astrophysics Data System (ADS)

The local, average and electronic structure of the semiconducting materials Si and Ge has been studied using multipole, maximum entropy method (MEM) and pair distribution function (PDF) analyses, using X-ray powder data. The covalent nature of bonding and the interaction between the atoms are clearly revealed by the two-dimensional MEM maps plotted on (1 0 0) and (1 1 0) planes and one-dimensional density along [1 0 0], [1 1 0] and [1 1 1] directions. The mid-bond electron densities between the atoms are 0.554 e/Å^{3} and 0.187 e/Å^{3} for Si and Ge respectively. In this work, the local structural information has also been obtained by analyzing the atomic pair distribution function. An attempt has been made in the present work to utilize the X-ray powder data sets to refine the structure and electron density distribution using the currently available versatile methods, MEM, multipole analysis and determination of pair distribution function for these two systems.

Saravanan, R.; Syed Ali, K. S.; Israel, S.

2008-04-01

376

Advanced analysis of metal distributions in human hair  

SciTech Connect

A variety of techniques (secondary electron microscopy with energy dispersive X-ray analysis, time-of-flight-secondary ion mass spectrometry, and synchrotron X-ray fluorescence) were utilized to distinguish metal contamination occurring in hair arising from endogenous uptake from an individual exposed to a polluted environment, in this case a lead smelter. Evidence was sought for elements less affected by contamination and potentially indicative of biogenic activity. The unique combination of surface sensitivity, spatial resolution, and detection limits used here has provided new insight regarding hair analysis. Metals such as Ca, Fe, and Pb appeared to have little representative value of endogenous uptake and were mainly due to contamination. Cu and Zn, however, demonstrate behaviors worthy of further investigation into relating hair concentrations to endogenous function.

Kempson, Ivan M.; Skinner, William M. (U. South Australia)

2008-06-09

377

Evolution History of Asteroid Itokawa Based on Block Distribution Analysis  

NASA Astrophysics Data System (ADS)

This work investigates trends in the global and regional distribution of blocks on asteroid 25143 Itokawa in order to discover new findings to better understand the history of this asteroid. Itokawa is a near-Earth object, and the first asteroid that was targeted for a sample return mission. Trends in block population provide new insights in regards to Itokawa's current appearance following the disruption of a possible parent body, and how its surface might have changed since then. Here blocks are defined as rocks or features with distinctive positive relief that are larger than a few meters in size. The size and distribution of blocks are measured by mapping the outline of the blocks using the Small Body Mapping Tool (SBMT) created by the Johns Hopkins University Applied Physics Laboratory [1]. The SBMT allows the user to overlap correctly geo-located Hayabusa images [2] onto the Itokawa shape model. This study provides additional inferences on the original disruption and subsequent re-accretion of Itokawa's "head" and "body" from block analyses. A new approach is taken by analyzing the population of blocks with respect to latitude for both Itokawa's current state, and a hypothetical elliptical body. Itokawa currently rotates approximately about its maximum moment of inertia, which is expected due to conservation of momentum and minimum energy arguments. After the possible disruption of the parent body of Itokawa, the "body" of Itokawa would have tended to a similar rotation. The shape of this body is made by removing the head of Itokawa and applying a semispherical cap. Using the method of [3] inertial properties of this object are calculated. With the assumption that this object had settled to its stable rotational axis, it is found that the pole axis could have been tilted about 13° away from the current axis in the direction opposite the head, equivalent to a 33 meter change in the center of mass. The results of this study provide means to test the hypothesis of whether or not Itokawa is a contact binary. References: [1] E. G. Kahn, et al. A tool for the visualization of small body data. In LPSC XLII, 2011. [2] A. Fujiwara, et al. The rubble-pile asteroid Itokawa as observed by Hayabusa. Science, 312(5778):1330-1334, June 2006. [3] A. F. Cheng, et al. Small-scale topography of 433 Eros from laser altimetry and imaging. Icarus, 155(1):51-74, 2002

Mazrouei, Sara; Daly, Michael; Barnouin, Olivier; Ernst, Carolyn

2013-04-01

378

Classification of cerebral lymphomas and glioblastomas featuring luminance distribution analysis.  

PubMed

Differentiating lymphomas and glioblastomas is important for proper treatment planning. A number of works have been proposed but there are still some problems. For example, many works depend on thresholding a single feature value, which is susceptible to noise. In other cases, experienced observers are required to extract the feature values or to provide some interactions with the system. Even if experts are involved, interobserver variance becomes another problem. In addition, most of the works use only one or a few slice(s) because 3D tumor segmentation is time consuming. In this paper, we propose a tumor classification system that analyzes the luminance distribution of the whole tumor region. Typical cases are classified by the luminance range thresholding and the apparent diffusion coefficients (ADC) thresholding. Nontypical cases are classified by a support vector machine (SVM). Most of the processing elements are semiautomatic. Therefore, even novice users can use the system easily and get the same results as experts. The experiments were conducted using 40 MRI datasets. The classification accuracy of the proposed method was 91.1% without the ADC thresholding and 95.4% with the ADC thresholding. On the other hand, the baseline method, the conventional ADC thresholding, yielded only 67.5% accuracy. PMID:23840280

Yamasaki, Toshihiko; Chen, Tsuhan; Hirai, Toshinori; Murakami, Ryuji

2013-06-06

379

Classification of Cerebral Lymphomas and Glioblastomas Featuring Luminance Distribution Analysis  

PubMed Central

Differentiating lymphomas and glioblastomas is important for proper treatment planning. A number of works have been proposed but there are still some problems. For example, many works depend on thresholding a single feature value, which is susceptible to noise. In other cases, experienced observers are required to extract the feature values or to provide some interactions with the system. Even if experts are involved, interobserver variance becomes another problem. In addition, most of the works use only one or a few slice(s) because 3D tumor segmentation is time consuming. In this paper, we propose a tumor classification system that analyzes the luminance distribution of the whole tumor region. Typical cases are classified by the luminance range thresholding and the apparent diffusion coefficients (ADC) thresholding. Nontypical cases are classified by a support vector machine (SVM). Most of the processing elements are semiautomatic. Therefore, even novice users can use the system easily and get the same results as experts. The experiments were conducted using 40 MRI datasets. The classification accuracy of the proposed method was 91.1% without the ADC thresholding and 95.4% with the ADC thresholding. On the other hand, the baseline method, the conventional ADC thresholding, yielded only 67.5% accuracy.

Yamasaki, Toshihiko; Chen, Tsuhan; Hirai, Toshinori; Murakami, Ryuji

2013-01-01

380

Motion synthesis and force distribution analysis for a biped robot.  

PubMed

In this paper, the method of generating biped robot motion using recorded human gait is presented. The recorded data were modified taking into account the velocity available for robot drives. Data includes only selected joint angles, therefore the missing values were obtained considering the dynamic postural stability of the robot, which means obtaining an adequate motion trajectory of the so-called Zero Moment Point (ZMT). Also, the method of determining the ground reaction forces' distribution during the biped robot's dynamic stable walk is described. The method was developed by the authors. Following the description of equations characterizing the dynamics of robot's motion, the values of the components of ground reaction forces were symbolically determined as well as the coordinates of the points of robot's feet contact with the ground. The theoretical considerations have been supported by computer simulation and animation of the robot's motion. This was done using Matlab/Simulink package and Simulink 3D Animation Toolbox, and it has proved the proposed method. PMID:21761810

Trojnacki, Maciej T; Zieli?ska, Teresa

2011-01-01

381

How extreme is extreme? An assessment of daily rainfall distribution tails  

NASA Astrophysics Data System (ADS)

The upper part of a probability distribution, usually known as the tail, governs both the magnitude and the frequency of extreme events. The tail behaviour of all probability distributions may be, loosely speaking, categorized in two families: heavy-tailed and light-tailed distributions, with the latter generating more "mild" and infrequent extremes compared to the former. This emphasizes how important for hydrological design is to assess correctly the tail behaviour. Traditionally, the wet-day daily rainfall has been described by light-tailed distributions like the Gamma, although heavier-tailed distributions have also been proposed and used, e.g. the Lognormal, the Pareto, the Kappa, and others. Here, we investigate the issue of tails for daily rainfall by comparing the upper part of empirical distributions of thousands of records with four common theoretical tails: those of the Pareto, Lognormal, Weibull and Gamma distributions. Specifically, we use 15 029 daily rainfall records from around the world with record lengths from 50 to 163 yr. The analysis shows that heavier-tailed distributions are in better agreement with the observed rainfall extremes than the more often used lighter tailed distributios, with clear implications on extreme event modelling and engineering design.

Papalexiou, S. M.; Koutsoyiannis, D.; Makropoulos, C.

2012-05-01

382

Correlation Spectroscopy of Minor Species: Signal Purification and Distribution Analysis  

SciTech Connect

We are performing experiments that use fluorescence resonance energy transfer (FRET) and fluorescence correlation spectroscopy (FCS) to monitor the movement of an individual donor-labeled sliding clamp protein molecule along acceptor-labeled DNA. In addition to the FRET signal sought from the sliding clamp-DNA complexes, the detection channel for FRET contains undesirable signal from free sliding clamp and free DNA. When multiple fluorescent species contribute to a correlation signal, it is difficult or impossible to distinguish between contributions from individual species. As a remedy, we introduce ''purified FCS'' (PFCS), which uses single molecule burst analysis to select a species of interest and extract the correlation signal for further analysis. We show that by expanding the correlation region around a burst, the correlated signal is retained and the functional forms of FCS fitting equations remain valid. We demonstrate the use of PFCS in experiments with DNA sliding clamps. We also introduce ''single molecule FCS'', which obtains diffusion time estimates for each burst using expanded correlation regions. By monitoring the detachment of weakly-bound 30-mer DNA oligomers from a single-stranded DNA plasmid, we show that single molecule FCS can distinguish between bursts from species that differ by a factor of 5 in diffusion constant.

Laurence, T A; Kwon, Y; Yin, E; Hollars, C; Camarero, J A; Barsky, D

2006-06-21

383

Differentiating cerebral lymphomas and GBMs featuring luminance distribution analysis  

NASA Astrophysics Data System (ADS)

Differentiating lymphomas and glioblastoma multiformes (GBMs) is important for proper treatment planning. A number of works have been proposed but there are still some problems. For example, many works depend on thresholding a single feature value, which is susceptible to noise. Non-typical cases that do not get along with such simple thresholding can be found easily. In other cases, experienced observers are required to extract the feature values or to provide some interactions to the system, which is costly. Even if experts are involved, inter-observer variance becomes another problem. In addition, most of the works use only one or a few slice(s) because 3D tumor segmentation is difficult and time-consuming. In this paper, we propose a tumor classification system that analyzes the luminance distribution of the whole tumor region. The 3D MRIs are segmented within a few tens of seconds by using our fast 3D segmentation algorithm. Then, the luminance histogram of the whole tumor region is generated. The typical cases are classified by the histogram range thresholding and the apparent diffusion coefficients (ADC) thresholding. The non-typical cases are learned and classified by a support vector machine (SVM). Most of the processing elements are semi-automatic except for the ADC value extraction. Therefore, even novice users can use the system easily and get almost the same results as experts. The experiments were conducted using 40 MRI datasets (20 lymphomas and 20 GBMs) with non-typical cases. The classification accuracy of the proposed method was 91.1% without the ADC thresholding and 95.4% with the ADC thresholding. On the other hand, the baseline method, the conventional ADC thresholding, yielded only 67.5% accuracy.

Yamasaki, Toshihiko; Chen, Tsuhan; Hirai, Toshinori; Murakami, Ryuji

2013-02-01

384

Environmental distribution, analysis, and toxicity of organometal(loid) compounds.  

PubMed

The biochemical modification of the metals and metalloids mercury, tin, arsenic, antimony, bismuth, selenium, and tellurium via formation of volatile metal hydrides and alkylated species (volatile and involatile) performs a fundamental role in determining the environmental processing of these elements. In most instances, the formation of such species increases the environmental mobility of the element, and can result in bioaccumulation in lipophilic environments. While inorganic forms of most of these compounds are well characterized (e.g., arsenic, mercury) and some of them exhibit low toxicity (e.g., tin, bismuth), the more lipid-soluble organometals can be highly toxic. Methylmercury poisoning (e.g., Minamata disease) and tumor development in rats after exposure to dimethylarsinic acid or tributyltin oxide are just some examples. Data on the genotoxicity (and the neurotoxicity) as well as the mechanisms of cellular action of organometal(loid) compounds are, however, scarce. Many studies have shown that the production of such organometal(loid) species is possible and likely whenever anaerobic conditions (at least on a microscale) are combined with available metal(loid)s and methyl donors in the presence of suitable organisms. Such anaerobic conditions can exist within natural environments (e.g., wetlands, pond sediments) as well as within anthropogenic environmental systems (e.g., waste disposal sites and sewage treatments plants). Some methylation can also take place under aerobic conditions. This article gives an overview about the environmental distribution of organometal(loid) compounds and the potential hazardous effects on animal and human health. Genotoxic effects in vivo and in vitro in particular are discussed. PMID:15239389

Dopp, E; Hartmann, L M; Florea, A M; Rettenmeier, A W; Hirner, A V

385

Exploiting Precedence Relations in the Schedulability Analysis of Distributed Real-Time Systems  

Microsoft Academic Search

In this paper we present improved techniques for the schedulability analysis of tasks with precedence relations in multiprocessor and distributed systems, scheduled under a preemptive fixed priority scheduler. Recently developed techniques, based on the analysis of tasks with dynamic offsets, take into account the precedence relations between tasks only indirectly, through terms iteratively estimated from the response times of the

José C. Palencia Gutiérrez; Michael González Harbour

1999-01-01

386

Image analysis method for determining 3-D size distribution of coarse aggregates  

Microsoft Academic Search

A new 3-D grain size distribution analysis method for coarse aggregates using image analysis is presented. The method is designed for a laboratory environment and requires no sieving, only imaging of the aggregate. A luminous background material eliminates unwanted shadow effects. Particles are placed so they are not touching, thus the images of the aggregates are of good quality allowing

J. M. R. Fernlund

2005-01-01

387

Derivation of the n'th order uncertainty analysis for normally distributed parameters  

Microsoft Academic Search

An n'th order uncertainty analysis methodology for problems involving generally correlated but normally distributed parameters is presented. All terms required to apply this uncertainty analysis methodology are expressed analytically in terms of the customary covariance matrices and in terms of up to the n'th order sensitivities.

Ronen

1985-01-01

388

Distributed transmission lines and time-domain analysis in SPICE-like circuit simulators  

Microsoft Academic Search

Several problems arising in the SPICE implementation of the time-domain analysis of circuits with distributed transmission lines are indicated. It is shown that some simple modifications of the original handling of transmission lines can significantly reduce both the memory requirements and the CPU time needed for this analysis. The modifications make it possible to trade simulation time for accuracy of

W. M. Zuberek; A. Konczykowska; H. Wang

1989-01-01

389

Distribution of trace elements in the human body determined by neutron activation analysis  

Microsoft Academic Search

Neutron activation analysis and instrumental semiconductor gamma-ray spectrometry were used for analysis of 20 trace elements in 10 autopsied human organs and tissues (liver, kidney, cerebrum, cerebellum, heart, muscle, pancreas, spleen, lung, and aorta) from 63 Japanese persons, whose ages ranged from 15 days to 85 yr. Distributions of aluminum, bromine, magnesium, manganese, rubidium, selenium, and vanadium in human body

M. Yukawa; M. Suzuki-Yasumoto; K. Amano; M. Terai

1980-01-01

390

Log Normal Distribution of Cellular Uptake of Radioactivity: Statistical Analysis of Alpha Particle Track Autoradiography  

PubMed Central

Recently, the distribution of radioactivity among a population of cells labeled with 210Po was shown to be well described by a log normal distribution function (J Nucl Med 47, 6 (2006) 1049-1058) with the aid of an autoradiographic approach. To ascertain the influence of Poisson statistics on the interpretation of the autoradiographic data, the present work reports on a detailed statistical analyses of these data. Methods The measured distributions of alpha particle tracks per cell were subjected to statistical tests with Poisson (P), log normal (LN), and Poisson – log normal (P – LN) models. Results The LN distribution function best describes the distribution of radioactivity among cell populations exposed to 0.52 and 3.8 kBq/mL 210Po-citrate. When cells were exposed to 67 kBq/mL, the P – LN distribution function gave a better fit, however, the underlying activity distribution remained log normal. Conclusions The present analysis generally provides further support for the use of LN distributions to describe the cellular uptake of radioactivity. Care should be exercised when analyzing autoradiographic data on activity distributions to ensure that Poisson processes do not distort the underlying LN distribution.

Neti, Prasad V.S.V.; Howell, Roger W.

2008-01-01

391

Distributional benefit analysis of a national air quality rule.  

PubMed

Under Executive Order 12898, the U.S. Environmental Protection Agency (EPA) must perform environmental justice (EJ) reviews of its rules and regulations. EJ analyses address the hypothesis that environmental disamenities are experienced disproportionately by poor and/or minority subgroups. Such analyses typically use communities as the unit of analysis. While community-based approaches make sense when considering where polluting sources locate, they are less appropriate for national air quality rules affecting many sources and pollutants that can travel thousands of miles. We compare exposures and health risks of EJ-identified individuals rather than communities to analyze EPA's Heavy Duty Diesel (HDD) rule as an example national air quality rule. Air pollutant exposures are estimated within grid cells by air quality models; all individuals in the same grid cell are assigned the same exposure. Using an inequality index, we find that inequality within racial/ethnic subgroups far outweighs inequality between them. We find, moreover, that the HDD rule leaves between-subgroup inequality essentially unchanged. Changes in health risks depend also on subgroups' baseline incidence rates, which differ across subgroups. Thus, health risk reductions may not follow the same pattern as reductions in exposure. These results are likely representative of other national air quality rules as well. PMID:21776207

Post, Ellen S; Belova, Anna; Huang, Jin

2011-06-01

392

A Multifractal Approach to the Analysis of Size-Frequency Distributions of Craters on Planetary Bodies  

NASA Astrophysics Data System (ADS)

We have developed a multifractal approach to the analysis of size-frequency distributions of craters on planetary surfaces. We demonstrate the use of the method and study the relationship between the multifractal spectrum and the size-frequency distribution of craters. We showed that if the multifractal spectrum of a crater size distribution can be approximated by a parabolic function, the size-frequency distribution of craters are lognormal. For demonstration of our approach we analyzed distributions of craters on selected Phobos areas using Mars Express HRSC images. We demonstrated that the distributions of the craters are very well approximated by lognormal curves, as our technique suggests. Using the multifractal approach we show that size-frequency distributions of small craters on the sub-Mars and anti-Mars sides of Phobos' surface appear to be different. We suggested that this approach may be used for analysis of size-frequency distributions of craters on other planetary bodies. This research was funded by the Ministry of Education and Science of the Russian Federation (MEGA-GRANT, Project name: "Geodesy, cartography and the study of planets and satellites", contract No. 11.G34.31.0021).

Uchaev, Dm. V.; Malinnikov, V. A.; Uchaev, D. V.; Oberst, J.

2012-04-01

393

Progress in Using the Generalized Wigner Distribution in the Analysis of Terrace-Width Distributions of Vicinal Surfaces  

NASA Astrophysics Data System (ADS)

The so-called generalized Wigner distribution (GWD) may provide at least as good a description of terrace width distributions (TWDs) on vicinal surfaces as the standard Gaussian fit.(T.L. Einstein and O. Pierre-Louis, Surface Sci. 424), L299 (1999). It works well for weak elastic repulsion strengths A between steps (where the latter fails), as illustrated explicitly(S.D. Cohen, H.L. Richards, TLE, and M. Giesen, cond- mat/9911319.) for vicinal Pt(110).( K. Swamy, E. Bertel, and I. Vilfan, Surface Sci. 425), L369 (1999). Applications to vicinal copper surfaces confirms the general viability of the new analysis procedure.(M. Giesen and T.L. Einstein, submitted to Surface Sci.) For troublesome data, we can treat the GWD as a two-parameter fit that allows the terrace widths to be scaled by an optimal effective mean width.^3 With Monte Carlo simulations we show that for physical values of A, the GWD provides a better overall estimate than the Gaussian models. We quantify how a GWD approaches a Gaussian for large A and present a convenient but accurate new expression relating the variance of the TWD to A.^3 We also mention how discreteness of terrace widths impacts the standard continuum analysis.^3

Cohen, S. D.; Richards, Howard L.; Einstein, T. L.

2000-03-01

394

Measurement of the particle spatial and velocity distributions in micro-abrasive jets  

NASA Astrophysics Data System (ADS)

Novel experimental techniques for obtaining the particle spatial distribution and the velocity distribution across a micro-abrasive jet were presented and tested. The spatial distribution of particles within the jet was found by using a direct particle capture technique, and was found to depend on the nozzle diameter, following either a Weibull or a piecewise Weibull distribution. In general, the jet was found to be more focused when more particles were present across the nozzle opening. It was demonstrated how the measured particle spatial distribution could be used with a measurement of the eroded profile to extract an estimate of the non-dimensional particle velocity distribution within the jet. Using this technique, a linear or nonlinear velocity distribution was obtained, depending on the particle type and the nozzle diameter used. The results for the velocity distribution were compared to particle tracking velocimetry (PTV) results and were found to be within the acceptable measurement error ranges.

Burzynski, T.; Papini, M.

2011-02-01

395

Hyperdimensional Analysis of Amino Acid Pair Distributions in Proteins  

PubMed Central

Our manuscript presents a novel approach to protein structure analyses. We have organized an 8-dimensional data cube with protein 3D-structural information from 8706 high-resolution non-redundant protein-chains with the aim of identifying packing rules at the amino acid pair level. The cube contains information about amino acid type, solvent accessibility, spatial and sequence distance, secondary structure and sequence length. We are able to pose structural queries to the data cube using program ProPack. The response is a 1, 2 or 3D graph. Whereas the response is of a statistical nature, the user can obtain an instant list of all PDB-structures where such pair is found. The user may select a particular structure, which is displayed highlighting the pair in question. The user may pose millions of different queries and for each one he will receive the answer in a few seconds. In order to demonstrate the capabilities of the data cube as well as the programs, we have selected well known structural features, disulphide bridges and salt bridges, where we illustrate how the queries are posed, and how answers are given. Motifs involving cysteines such as disulphide bridges, zinc-fingers and iron-sulfur clusters are clearly identified and differentiated. ProPack also reveals that whereas pairs of Lys residues virtually never appear in close spatial proximity, pairs of Arg are abundant and appear at close spatial distance, contrasting the belief that electrostatic repulsion would prevent this juxtaposition and that Arg-Lys is perceived as a conservative mutation. The presented programs can find and visualize novel packing preferences in proteins structures allowing the user to unravel correlations between pairs of amino acids. The new tools allow the user to view statistical information and visualize instantly the structures that underpin the statistical information, which is far from trivial with most other SW tools for protein structure analysis.

Henriksen, Svend B.; Arnason, Omar; Soring, Jon; Petersen, Steffen B.

2011-01-01

396

Strength Improvement on an Imaginary SiC Fiber of Ideal Diameter and Reduced Internal Defects Estimated from the Weibull Scaling of Tyranno ZMI Fiber  

NASA Astrophysics Data System (ADS)

The size effect of the diameter has been assessed for the tensile strength of Tyranno ZMI fiber. Uniform diameter section in sample fibers has been selected as tensile test sample. The single fibers of measured diameters have been tensile tested to provide two groups of data, i.e., “small diameter” group and “large diameter” group. The parameters of single-modal Weibull model showed inconsistency on the two groups, thus the Weibull parameters have shown the dependence on the sample diameter. Scanning electron microscope (SEM) analyses had revealed characteristic fracture patterns of “extremely weak” samples only in “large diameter” group. The key information for improving the reliability was then discussed through coupling the Weibull scaling and the fracture surface analyses. The potential in the strength improvement has been assessed for an imaginary fiber, which does not contain the sources of the characteristic fracture patterns.

Morimoto, Tetsuya; Yamamoto, Koji; Ogihara, Shinji

397

A Geoinformatics Approach to LiDAR \\/ ALSM Data Distribution, Interpolation, and Analysis  

Microsoft Academic Search

Distribution, interpolation and analysis of large LiDAR (Light Distance And Ranging, also known as ALSM (Airborne Laser Swath Mapping)) datasets pushes the computational limits of typical data distribution and processing systems. The high point-density of LiDAR datasets makes grid interpolation difficult for geoscience users who lack the computing and software resources necessary to handle these massive data volumes. We are

C. J. Crosby; J. Conner; E. Frank; J. R. Arrowsmith; A. Memon; V. Nandigam; G. Wurman; C. Baru

2005-01-01

398

Autoradiographic analysis of monoclonal antibody distribution in human colon and breast tumor xenografts  

Microsoft Academic Search

The targeting of monoclonal antibodies to human tumor xenografts in nude mice was investigated by analysis of the cellular distribution of two radioiodinated monoclonal antibodies, B6.2 and B72.3, which recognize different tumor-associated antigens. The time course of distribution of each antibody within Clouser human mammary carcinoma (B6.2 positive, B72.3 negative) and LS174T human colorectal carcinoma (B6.2 positive, B72.3 positive) following

Peter L. Jones; Brian M. Gallagher; Howard Sands

1986-01-01

399

Measurement of Brillouin frequency shift distribution in PLC by Brillouin optical correlation domain analysis  

NASA Astrophysics Data System (ADS)

We have measured Brillouin frequency shift distribution in a planar lightwave circuit (PLC) by Brillouin optical correlation domain analysis (BOCDA). We have made an experimental system specialized for the measurement of PLC, realizing spatial resolution of 5.9mm with standard deviation of 0.34MHz in Brillouin frequency shift (BFS) measurement. From the data obtained in the experiments, we have found that the BFS distribution shape along the waveguide corresponds to its route pattern in the PLC.

Hotate, Kazuo; Watanabe, Ryuji; He, Zuyuan; Kishi, Masato

400

Distribution patterns of firearm discharge residues as revealed by neutron activation analysis  

Microsoft Academic Search

A systematic investigation using a variety of handguns has revealed the existence of distinguishable distribution patterns\\u000a of firearm discharge residues on surfaces below the flight path of a bullet. The residues are identifiable even at distances\\u000a of 12 meters from the gun using nondestructive neutron activation analysis. The results of these investigations show that\\u000a the distribution pattern for a gun

K. K. S. Pillay; D. C. Driscoll; W. A. Jester

1975-01-01

401

Spatiotemporal analysis of endocytosis and membrane distribution of fluorescent sterols in living cells  

Microsoft Academic Search

Distribution and dynamics of cholesterol in the plasma membrane as well as internalization pathways for sterol from the cell\\u000a surface are of great cell biological interest. Here, UV-sensitive wide field microscopy of the intrinsically fluorescent sterols,\\u000a dehydroergosterol (DHE) and cholestatrienol (CTL) combined with advanced image analysis were used to study spatiotemporal\\u000a sterol distribution in living macrophages, adipocytes and fibroblasts. Sterol

Daniel Wüstner; Nils J. Færgeman

2008-01-01

402

Robust Bayesian Analysis of Heavy-tailed Stochastic Volatility Models using Scale Mixtures of Normal Distributions  

PubMed Central

A Bayesian analysis of stochastic volatility (SV) models using the class of symmetric scale mixtures of normal (SMN) distributions is considered. In the face of non-normality, this provides an appealing robust alternative to the routine use of the normal distribution. Specific distributions examined include the normal, student-t, slash and the variance gamma distributions. Using a Bayesian paradigm, an efficient Markov chain Monte Carlo (MCMC) algorithm is introduced for parameter estimation. Moreover, the mixing parameters obtained as a by-product of the scale mixture representation can be used to identify outliers. The methods developed are applied to analyze daily stock returns data on S&P500 index. Bayesian model selection criteria as well as out-of- sample forecasting results reveal that the SV models based on heavy-tailed SMN distributions provide significant improvement in model fit as well as prediction to the S&P500 index data over the usual normal model.

Abanto-Valle, C. A.; Bandyopadhyay, D.; Lachos, V. H.; Enriquez, I.

2009-01-01

403

Exploring the Sensitivity of Horn's Parallel Analysis to the Distributional Form of Random Data  

PubMed Central

Horn’s parallel analysis (PA) is the method of consensus in the literature on empirical methods for deciding how many components/factors to retain. Different authors have proposed various implementations of PA. Horn’s seminal 1965 article, a 1996 article by Thompson and Daniel, and a 2004 article by Hayton et al., all make assertions about the requisite distributional forms of the random data generated for use in PA. Readily available software is used to test whether the results of PA are sensitive to several distributional prescriptions in the literature regarding the rank, normality, mean, variance, and range of simulated data on a portion of the National Comorbidity Survey Replication (Pennell et al., 2004) by varying the distributions in each PA. The results of PA were found not to vary by distributional assumption. The conclusion is that PA may be reliably performed with the computationally simplest distributional assumptions about the simulated data.

Dinno, Alexis

2009-01-01

404

Advancing the identification and evaluation of distributed rainfall-runoff models using global sensitivity analysis  

NASA Astrophysics Data System (ADS)

This study provides a step-wise analysis of a conceptual grid-based distributed rainfall-runoff model, the United States National Weather Service (US NWS) Hydrology Laboratory Research Distributed Hydrologic Model (HL-RDHM). It evaluates model parameter sensitivities for annual, monthly, and event time periods with the intent of elucidating the key parameters impacting the distributed model's forecasts. This study demonstrates a methodology that balances the computational constraints posed by global sensitivity analysis with the need to fully characterize the HL-RDHM's sensitivities. The HL-RDHM's sensitivities were assessed for annual and monthly periods using distributed forcing and identical model parameters for all grid cells at 24-hour and 1-hour model time steps respectively for two case study watersheds within the Juniata River Basin in central Pennsylvania. This study also provides detailed spatial analysis of the HL-RDHM's sensitivities for two flood events based on 1-hour model time steps selected to demonstrate how strongly the spatial heterogeneity of forcing influences the model's spatial sensitivities. Our verification analysis of the sensitivity analysis method demonstrates that the method provides robust sensitivity rankings and that these rankings could be used to significantly reduce the number of parameters that should be considered when calibrating the HL-RDHM. Overall, the sensitivity analysis results reveal that storage variation, spatial trends in forcing, and cell proximity to the gauged watershed outlet are the three primary factors that control the HL-RDHM's behavior.

Tang, Y.; Reed, P.; van Werkhoven, K.; Wagener, T.

2007-06-01

405

Investigation of Dielectric Breakdown Characteristics for Double-break Vacuum Interrupter and Dielectric Breakdown Probability Distribution in Vacuum Interrupter  

NASA Astrophysics Data System (ADS)

To investigate the reliability of equipment of vacuum insulation, a study was carried out to clarify breakdown probability distributions in vacuum gap. Further, a double-break vacuum circuit breaker was investigated for breakdown probability distribution. The test results show that the breakdown probability distribution of the vacuum gap can be represented by a Weibull distribution using a location parameter, which shows the voltage that permits a zero breakdown probability. The location parameter obtained from Weibull plot depends on electrode area. The shape parameter obtained from Weibull plot of vacuum gap was 10?14, and is constant irrespective non-uniform field factor. The breakdown probability distribution after no-load switching can be represented by Weibull distribution using a location parameter. The shape parameter after no-load switching was 6?8.5, and is constant, irrespective of gap length. This indicates that the scatter of breakdown voltage was increased by no-load switching. If the vacuum circuit breaker uses a double break, breakdown probability at low voltage becomes lower than single-break probability. Although potential distribution is a concern in the double-break vacuum cuicuit breaker, its insulation reliability is better than that of the single-break vacuum interrupter even if the bias of the vacuum interrupter's sharing voltage is taken into account.

Shioiri, Tetsu; Asari, Naoki; Sato, Junichi; Sasage, Kosuke; Yokokura, Kunio; Homma, Mitsutaka; Suzuki, Katsumi

406

Size distribution of magnetic iron oxide nanoparticles using Warren-Averbach XRD analysis  

NASA Astrophysics Data System (ADS)

We use the Fourier transform based Warren-Averbach (WA) analysis to separate the contributions of X-ray diffraction (XRD) profile broadening due to crystallite size and microstrain for magnetic iron oxide nanoparticles. The profile shape of the column length distribution, obtained from WA analysis, is used to analyze the shape of the magnetic iron oxide nanoparticles. From the column length distribution, the crystallite size and its distribution are estimated for these nanoparticles which are compared with size distribution obtained from dynamic light scattering measurements. The crystallite size and size distribution of crystallites obtained from WA analysis are explained based on the experimental parameters employed in preparation of these magnetic iron oxide nanoparticles. The variation of volume weighted diameter (Dv, from WA analysis) with saturation magnetization (Ms) fits well to a core shell model wherein it is known that Ms=Mbulk(1-6g/Dv) with Mbulk as bulk magnetization of iron oxide and g as magnetic shell disorder thickness.

Mahadevan, S.; Behera, S. P.; Gnanaprakash, G.; Jayakumar, T.; Philip, J.; Rao, B. P. C.

2012-07-01

407

Analysis of axially non-uniform loss distribution in 3-phase induction motor considering skew effect  

SciTech Connect

This paper discusses the phenomena of the axially non-uniform distribution of magnetic flux densities and losses in a 3-phase squirrel cage induction motor of which the rotor bars are skewed. A 2-dimensional complex finite element method taking account of the effects of the skewed rotor bars is utilized for the analysis of characteristics such as copper and iron losses and the loss distributions are examined. The summing up values of non-uniform losses resulted from the finite element analysis are compared with measurement values.

Kown, B.I.; Kim, B.T.; Jun, C.S.; Park, S.C. (Hanyang Univ., Ansan (Korea, Republic of))

1999-05-01

408

The Analysis of the Strength, Distribution and Direction for the EEG Phase Synchronization by Musical Stimulus  

NASA Astrophysics Data System (ADS)

In this study, we propose the EEG phase synchronization analysis including not only the average strength of the synchronization but also the distribution and directions under the conditions that evoked emotion by musical stimuli. The experiment is performed with the two different musical stimuli that evoke happiness or sadness for 150 seconds. It is found that the average strength of synchronization indicates no difference between the right side and the left side of the frontal lobe during the happy stimulus, the distribution and directions indicate significant differences. Therefore, proposed analysis is useful for detecting emotional condition because it provides information that cannot be obtained only by the average strength of synchronization.

Ogawa, Yutaro; Ikeda, Akira; Kotani, Kiyoshi; Jimbo, Yasuhiko

409

Distribution regularity of breakdown field strength of high voltage ceramic capacitor  

Microsoft Academic Search

Electrical breakdown tests on high voltage ceramic capacitors, whose ceramic disks were in two kind of geometry, were carried out under various rates of voltage rise. It was shown that the breakdown field strength of samples in the same form displayed a Weibull distribution for the same rate of voltage rise. With increasing rate, the slope and character strength of

Liu Bin; Chen Wei; Zhang Yajie; Chen Shoutian

2000-01-01

410

Determining fertilizer-induced NO emission ratio from soils by a statistical distribution model  

Microsoft Academic Search

To reduce uncertainties in the highly variable estimates of NO emission from N fertilizer, we compiled and analyzed available reports of field measurements on fertilizer-induced NO emission. Three statistical distribution models, lognormal, gamma and Weibull, were used to fit the observation data. Results show that while all three models fit the observation data statistically, the lognormal model is not applicable

Xiaoyuan Yan; Kunio Shimizu; Hajime Akimoto; Toshimasa Ohara

2003-01-01

411

Strength distributions and size effects for 2D and 3D composites with Weibull fibers in an elastic matrix  

Microsoft Academic Search

Monte Carlo simulation and theoretical modeling are used to study the statistical failure modes in unidirectional composites consisting of elastic fibers in an elastic matrix. Both linear and hexagonal fiber arrays are considered, forming 2D and 3D composites, respectively. Failure is idealized using the chain-of-bundles model in terms of d-bundles of length d, which is the length-scale of fiber load

Sivasambu Mahesh; S. Leigh Phoenix; Irene J. Beyerlein

2002-01-01

412

Strength distributions and size effects for 2D and 3D composites with Weibull fibers in an elastic matrix  

Microsoft Academic Search

Monte Carlo simulation and theoretical modeling are used to study the statistical failure modes in unidirectional composites consisting of elastic bers in an elastic matrix. Both linear and hexagonal ber arrays are considered, forming 2D and 3D composites, respectively. Failure is idealized using the chain-of-bundles model in terms of -bundles of length , which is the length-scale of ber load

SIVASAMBU MAHESH; S. LEIGH PHOENIX; IRENE J. BEYERLEIN

2002-01-01

413

An Extension of Economic Design of x-Bar Control Charts for Non Normally Distributed Data Under Weibull Shock Models  

Microsoft Academic Search

Three parameters—sample size, sampling intervals, and the control limits—must be determined when the x bar chart to monitor a manufacturing process. The constant sampling intervals were widely employed because of its administrative simplicity. However, the variable sampling interval (VSI) has recently been shown to give substantially faster detection of most process shifts than fixed-sampling-interval (FSI) for x-bar charts. In addition,

Li Lun Yeh; Peng Kai Wang; Feng Chia Li; Yu Mei Yeh

2011-01-01

414

Energy Engineering Analysis Program, Limited Energy Study of Steam Distribution Systems, Hawthorne Army Ammunition Depot, Hawthorne, Nevada.  

National Technical Information Service (NTIS)

This report summarizes all work of the Limited Energy Study of Steam Distribution Systems, Energy Engineering Analysis Program, Hawthorne Army Ammunition Depot (HWAAD), Nevada. The purpose of this limited energy study is to evaluate steam distribution and...

1995-01-01

415

Empirical significance values for linkage analysis: trait simulation using posterior model distributions from MCMC oligogenic segregation analysis.  

PubMed

Variance-components (VC) linkage analysis is a powerful model-free method for assessing linkage, but the distribution of VC logarithm of the odds ratio (LOD) scores may deviate substantially from the assumed asymptotic distribution. Typically, the null distribution of the VC-LOD score and other linkage statistics has been estimated by generating new genotype data independently of the trait data, and computing a linkage statistic for many such marker-simulated data sets. However, marker simulation is susceptible to errors in the assumed marker and map model and is computationally intensive. Here, we describe a method for generating posterior distributions of linkage statistics through simulation of trait data based on the original sample and on results from an initial scan using a Bayesian Markov-chain Monte Carlo (MCMC) approach for oligogenic segregation analysis. We use samples of oligogenic trait models taken from the posterior distribution to generate new samples of trait data, which were paired with the original marker data for analysis. Empirical P-values obtained from trait and marker simulation were similar when derived for several strong linkage signals from published linkage scans, and for analysis of data with a known, simulated, trait model. Furthermore, trait simulation produces the expected null distribution of VC-LOD scores and is computationally fast when marker identity-by-descent estimates from the original data could be reused. These results suggest that trait simulation gives valid estimates of statistical significance of linkage signals. Finally, these results also demonstrate the feasibility of obtaining empirical significance levels for evaluating Bayesian oligogenic linkage signals with either marker or trait simulation. PMID:17849492

Igo, Robert P; Wijsman, Ellen M

2008-02-01

416

The use of grain size distribution analysis of sediments and soils in forensic enquiry.  

PubMed

The use of grain size distribution analysis in forensic enquiry was investigated with reference to four forensic case studies which contained the type of sample restraints and limitations often encountered in criminal case work. The problems of the comparison of trace and bulk samples are outlined and the need for multiple sample analysis is highlighted. It was found that the problems of soil analysis, particularly when the soil was recovered from anthropogenic sources, focused on the lack of identification of pre-, syn- and post-forensic event mixing of materials, thus obscuring the recognition of false-negative or false-positive exclusions between samples. It was found that grain size distribution analysis was a useful descriptive tool but it was concluded that if it were to be used in any other manner the derived results should be treated with great caution. The statistical analyses of these data did not improve the quality of the interpretation of the results. PMID:18051034

Morgan, R M; Bull, P A

2007-11-01

417

When the Tail Counts: The Advantage of Bilingualism Through the Ex-Gaussian Distribution Analysis  

PubMed Central

Several studies have documented the advantage of bilingualism with respect to the development of the executive control (EC) system. Two effects of bilingualism have been described in conflict resolution tasks: (a) bilinguals tend to perform the tasks faster overall, and (b) bilinguals tend to experience less interference from conflicting information, compared to monolinguals. The precise way in which the bilingual advantage relies on different EC mechanisms is still not well understood. The goal of the present article is to further explore how bilingualism impacts the EC system by performing a new analysis (Ex-Gaussian) of already reported data in which bilinguals and monolinguals performed a flanker task. Ex-Gaussian distribution analysis allows us to partial out the contribution of the normal and the exponential components of the RT distribution of the two groups. The fit of the raw data to the ex-Gaussian distribution showed two main results. First, we found that the bilingualism advantage in the overall speed of processing is captured by group differences in the normal (?) and the exponential (?) components of the distribution. Second, the bilingual advantage in the magnitude of the conflict effect is captured by group differences only in the exponential component. The results are discussed in terms of: (a) usefulness of the ex-Gaussian analysis as a tool to better describe the RT distribution, and (b) a new approach to explore the cognitive processes purportedly involved in instantiating the bilingualism advantage with respect to EC.

Calabria, Marco; Hernandez, Mireia; Martin, Clara D.; Costa, Albert

2011-01-01

418

Behavioral Analysis of Mobile Robot Trajectories Using a Point Distribution Model  

Microsoft Academic Search

\\u000a In recent years, the advent of robust tracking systems has enabled behavioral analysis of individuals based on their trajectories.\\u000a An analysis method based on a Point Distribution Model (PDM) is presented here. It is an unsupervised modeling of the trajectories\\u000a in order to extract behavioral features. The applicability of this method has been demonstrated on trajectories of a realistically\\u000a simulated

Pierre Roduit; Alcherio Martinoli; Jacques Jacot

2006-01-01

419

Analysis of solute distribution in dendrites of carbon steel with ?\\/? transformation during solidification  

Microsoft Academic Search

Solute distribution in dendrites during solidification of carbon steel was analyzed by unidirectional solidification experiments\\u000a and mathematical analysis. The characteristic of the mathematical analysis is that diffusion of solutes in solid and redistribution\\u000a of solutes at solid\\/liquid and?\\/? interfaces are taken into consideration. Based on the observed and calculated results, it was found that phosphorus was redistributed\\u000a from?-phase to?-phase, and

Yoshiyuki Ueshima; Shozo Mizoguchi; Tooru Matsumiya; Hiroyuki Kajioka

1986-01-01

420

The AIDA toolset for design and implementation analysis of distributed real-time control systems  

Microsoft Academic Search

This article introduces a toolset that integrates the design and performance analysis of control systems with embedded real-time system design. The toolset enables specification and analysis of real-time implementations of control applications. Control system designs are imported to a real-time system-modelling domain in which the functionality is distributed on a target computer system. The control functionality is partitioned into operating

Ola Redell; Jad El-khoury; Martin Törngren

2004-01-01

421

Fuzzy Cluster Analysis of Regional City Multilevel Logistics Distribution Center Location Plan  

Microsoft Academic Search

\\u000a Establish the cities multi-level logistics distribution center in the region to improve the flow efficiency and economic benefits,\\u000a enhance regional competitiveness, promote the rational allocation of regional resources and effective use has an important\\u000a role. This article use fuzzy clustering analysis method to study. First discusses the preparations of fuzzy clustering analysis.\\u000a includes the construction of influence Factors indicator system,

Yong-chang Ren; Tao Xing; Qiang Quan; Guo-qiang Zhao

422

Strategic Sequencing for State Distributed PV Policies: A Quantitative Analysis of Policy Impacts and Interactions  

SciTech Connect

State and local policymakers show increasing interest in spurring the development of customer-sited distributed generation (DG), in particular solar photovoltaic (PV) markets. Prompted by that interest, this analysis examines the use of state policy as a tool to support the development of a robust private investment market. This analysis builds on previous studies that focus on government subsidies to reduce installation costs of individual projects and provides an evaluation of the impacts of policies on stimulating private market development.

Doris, E.; Krasko, V.A.

2012-10-01

423

Comprehensive neutron cross-section and secondary energy distribution uncertainty analysis for a fusion reactor  

Microsoft Academic Search

On the example of General Atomic's well-documented Power Generating Fusion Reactor (PGFR) design, this report exercises a comprehensive neutron cross-section and secondary energy distribution (SED) uncertainty analysis. The LASL sensitivity and uncertainty analysis code SENSIT is used to calculate reaction cross-section sensitivity profiles and integral SED sensitivity coefficients. These are then folded with covariance matrices and integral SED uncertainties to

S. A. W. Gerstl; R. J. LaBauve; P. G. Young

1980-01-01

424

Analysis of Current Distribution in Driving Multiple Cold Cathode Fluorescent Lamps (CCFL)  

Microsoft Academic Search

Cold cathode fluorescent lamps (CCFLs) show complex characteristics, which make it difficult to drive them in parallel. In this paper, a backlight inverter, which can drive multiple CCFLs using single controller and single switching network, is presented. The analysis of the lamp current distribution is presented in detail. The current-balancing condition, under which the lamp currents are well balanced in

Chang-Gyun Kim; Kyu-Chan Lee; Bo H. Cho

2007-01-01

425

Analysis, tuning and comparison of two general sparse solvers for distributed memory computers.  

National Technical Information Service (NTIS)

We describe the work performed in the context of a Franco-Berkeley funded project between NERSC-LBNL located in Berkeley (USA) and CERFACS-ENSEEIHT located in Toulouse (France). We discuss both the tuning and performance analysis of two distributed memory...

P. R. Amestoy I. S. Duff J. Y. L'Excellent X. S. Li

2000-01-01

426

A methodology and tool for performance analysis of distributed server systems  

Microsoft Academic Search

We present a methodology and tool for performance analysis of distributed server systems, which allows high-level specification of the system, and generates and solves the underlying queueing network model. Our approach is different from the existing ones in that the specification captures the natural manner in which application servers are deployed on machines and machines are deployed on networks. The

Rukma V. Prabhu Verlekar; Varsha Apte

2006-01-01

427

Data communications and management of a distributed network of automated data acquisition and analysis systems  

Microsoft Academic Search

Several research applications require the deployment of a distributed network of automated data acquisition and analysis systems. These systems must provide a reliable and robust method of transferring acquired data to an appropriate data center. The data center must be capable of forwarding the acquired data to a potentially large group of researchers. The network's system operators need robust tools

A. D. Mckinnon; C. W. Hubbard

1997-01-01

428

Distributional analysis of regional benefits and cost of air quality control  

Microsoft Academic Search

The methodology and results of an analysis of benefits and costs of air quality control for an urban region in Florida are given. The machinery used considers the spatial distribution of: (a) emission sources; (b) the ambient levels resulting from local meteorological conditions and geographic features; and (c) the socioeconomic characteristics of the impacted population groups. This facilitates an examination

E. T. Loehman; S. V. Berg; A. A. Arroyo; R. A. Hedinger; J. M. Schwartz; M. E. Shaw; R. W. Fahien; V. H. De; R. P. Fishe; D. E. Rio

1979-01-01

429

Reconstructing Pre-Fragmentation Bubble Size Distributions from Volcanic Ash using Stereo SEM Analysis  

Microsoft Academic Search

We have conducted an analysis of bubble (BSD) and ash particle (PSD) size distributions for ashes from two contrasting eruptions. The first is the May, 1980 eruption of Mt. St. Helens (MSH), a dacitic plinian eruption that spread ash over a large area of the Western U.S. The second is the basaltic sub-plinian 1974 eruption of Fuego (Guatemala), which was

D. L. Sahagian; A. A. Proussevitch; G. K. Mulukutla; K. Genareau

2010-01-01

430

Analysis of a cone-based distributed topology control algorithm for wireless multi-hop networks  

Microsoft Academic Search

The topology of a wireless multi-hop network can be controlled by varying the transmission power at each node. In this paper, we give a detailed analysis of a cone-based distributed topology control algorithm. This algorithm, introduced in [16], does not assume that nodes have GPS information available; rather it depends only on directional information. Roughly speaking, the basic idea of

Li Li; Joseph Y. Halpern; Paramvir Bahl; Yi-Min Wang; Roger Wattenhofer

2001-01-01

431

Geomorphic features of a badland (biancane) area (Central Italy): characterisation, distribution and quantitative spatial analysis  

Microsoft Academic Search

The biancana landscapes, rather common in several Italian areas, have a very complex morphology. Different geomorphic features often occur along the same hillslope. From a morphological survey of an experimental site in southern Tuscany, the forms were classified, and their distribution analysed. Spatial analysis of the biancane provided insights into the range of forces responsible for their formation and evolution.

Costanza Calzolari; Fabrizio Ungaro

1998-01-01

432

Modeling and Performance Analysis of a Microturbine as a Distributed Energy Resource  

Microsoft Academic Search

This paper presents modeling, simulation, and analysis of load following behavior of a microturbine (MT) as a distributed energy resource (DER). The MT-generator (MTG) system consists of the MT coupled to a synchronous generator. Simulation is done in MATLAB for different loading conditions under islanded and grid-connected modes. The MTG model also incorporates a speed controller for maintaining constant speed

A. K. Saha; S. Chowdhury; P. A. Crossley

2009-01-01

433

An investigation on the intra-sample distribution of cotton color by using image analysis  

Technology Transfer Automated Retrieval System (TEKTRAN)

The colorimeter principle is widely used to measure cotton color. This method provides the sample’s color grade; but the result does not include information about the color distribution and any variation within the sample. We conducted an investigation that used image analysis method to study the ...

434

Identification of distributed metabolic objectives in the hypermetabolic liver by flux and energy balance analysis  

Microsoft Academic Search

A methodology for inferring distributed metabolic objectives from time series flux data is developed by combining metabolic flux analysis, pathway identification, free energy balances, and nested optimization. This methodology is used to investigate the metabolic response of the rat liver to burn injury-induced whole body inflammation. Gibbs free energy changes were computed for stoichiometrically balanced sequences of reactions, or pathways,

Ryan P. Nolan; Andrew P. Fenley; Kyongbum Lee

2006-01-01

435

The distribution of fluorine and other elements in teeth using proton induced reaction analysis techniques  

Microsoft Academic Search

Proton induced gamma-ray emission (PIGE) and proton induced X-ray emission (PIXE) analysis was employed to investigate the distribution of the concentration of fluorine and ten other elements along sections of teeth samples, extracted from eight individuals. These sections which included the bulk of dentine and enamel were scanned using a proton beam of 250 m diameter. Rutberford backscattering spectra were

W. Arshed; O. A. Akanle; N. M. Spyrou

1994-01-01

436

Quo vadis efficiency analysis of water distribution? A comparative literature review  

Microsoft Academic Search

Recognizing the growing importance of scientific benchmarking in water distribution, we provide a comprehensive survey of the available literature. We begin with a discussion about the (limited) use of benchmarking in the regulation of UK water utilities, and then extend the analysis to regulated water sectors in other countries. We find no clear impact of public or private ownership; instead,

Matthias Walter; Astrid Cullmann; Christian von Hirschhausen; Robert Wand; Michael Zschille

2009-01-01

437

Critical Path Analysis for the Execution of Parallel and Distributed Programs  

Microsoft Academic Search

The authors present the design, implementation, and testing of the critical path analysis technique using the IPS performance measurement tool for parallel and distributed programs. They create a precedence graph of a program's activities (program activity graph) with the data collected during the execution of a program. The critical path, the longest path in the program activity graph, represents the

Cui-qing Yang; Barton P. Miller

1988-01-01

438

Elemental regional distribution in human brain tumours - PIXE analysis of biopsy and autopsy samples  

NASA Astrophysics Data System (ADS)

The elemental regional distribution in human brain tissue was obtained using PIXE analysis. A histo-pathological investigation was used to classify the samples into three different groups: (1) normal tissue, (2) tumour front and (3) tumour centre. Significant differences between the mean values of phosphorous, calcium, iron, zinc and selenium concentrations in each group are reported.

Tapper, U. A. S.; Malmqvist, K. G.; Brun, A.; Salford, L. G.

1987-03-01

439

Parallel and distributed solutions for contingency analysis in energy management systems  

Microsoft Academic Search

This paper discusses and compares the use of parallel computers and distributed networks of computers as a means of solving the contingency analysis problem in an energy management system environment. The paper reports results obtained with a difficult real-life system (the South-Southeastern Brazilian interconnected network with 810 buses). Performance indices such as speedups and processor efficiencies are discussed in the

A. C. B. Alves; A. Monticelli

1995-01-01

440

The Asymptotic Normal Distribution of Estimators in Factor Analysis under General Conditions  

Microsoft Academic Search

Asymptotic properties of estimators for the confirmatory factor analysis model are discussed. The model is identified by restrictions on the elements of the factor loading matrix; the number of restrictions may exceed that required for identification. It is shown that a particular centering of the maximum likelihood estimator derived under assumed normality of observations yields an asymptotic normal distribution that

T. W. Anderson; Yasuo Amemiya

1988-01-01

441

A Simplified Approach for Load Flow Analysis of Radial Distribution Network  

Microsoft Academic Search

This paper presents a simple approach for load flow analysis of a radial distribution network. The proposed approach utilizes forward and backward sweep algorithm based on Kirchoff's current law (KCL) and Kirchoff's voltage law (KVL) for evaluating the node voltages iteratively. In this approach, computation of branch current depends only on the current injected at the neighbouring node and the

K. Vinoth Kumar; M. P. Selvan

2008-01-01

442

A simplified approach for load flow analysis of radial distribution network with embedded generation  

Microsoft Academic Search

This paper presents a simple approach for load flow analysis of a radial distribution network with embedded generation. The proposed approach utilizes forward and backward sweep algorithm based on Kirchoffpsilas current law (KCL) and Kirchoffpsilas voltage law (KVL) for evaluating the node voltages iteratively. In this approach, computation of branch current depends only on the current injected at the neighbouring

K Vinoth Kumar; M. P. Selvan

2008-01-01

443

Performance modelling and analysis of distributed access network system using DEVSim++  

Microsoft Academic Search

DEVSim++ is a C++ based, object-oriented modeling\\/simulation environment which realizes the hierarchical, modular DEVS formalism for discrete event systems specification. This paper describes a methodology for performance modeling and analysis of a distributed access network system under development within the DEVSim++ environment. The methodology develops performance models for the system using the DEVS framework and implement the models in C++.

Kyoix Ho Lee; Tag Gon Kim

1994-01-01

444

Contain analysis of hydrogen distribution and combustion in PWR dry containments  

Microsoft Academic Search

Hydrogen transport and combustion in a PWR dry containment are analyzed using the CONTAIN code for a multi-compartment model of the Zion plant. The analysis includes consideration of both degraded core and full core meltdown accidents initiated by a small break LOCA. The importance of intercell flow mixing on distributions of gas composition and temperature in various compartments are evaluated.

J. W. Yang; S. Nimnual

1991-01-01

445

Method for Quantitative Analysis of Glycosaminoglycan Distribution in Cultured Natural and Engineered Cartilage  

Microsoft Academic Search

Cartilage tissue engineering can provide a valuable tool for controlled studies of tissue development. As an example, analysis of the spatial distribution of glycosaminoglycans (GAG) in sections of cartilaginous tissues engineered under different culture conditions could be used to correlate the effects of environmental factors with the structure of the regenerated tissue. In this paper we describe a computer-based technique

Ivan Martin; Bojana Obradovic; Lisa E. Freed; Gordana Vunjak-Novakovic

1999-01-01

446

The Robustness of 2SLS Estimation of a Non-normally Distributed Confirmatory Factor Analysis Model.  

ERIC Educational Resources Information Center

|A Monte Carlo study was conducted to assess the robustness of the limited information two-stage least squares (2SLS) estimation procedure on a confirmatory factor analysis model with nonnormal distributions. Full information maximum likelihood methods were used for comparison. One hundred model replications were used to generate data. (TJH)|

Brown, R. L.

1990-01-01

447

Analysis of Time Distribution in Traffic Accident Based on Fuzzy Assessment Method  

Microsoft Academic Search

In light of China's traffic accident status much; this paper focuses on the problem of reducing the occurrence of traffic accidents. Based on the traffic accident data within a year in certain section of Tianjin, this paper studies the application of fuzzy assessment method in analysis of time distribution of traffic accidents. We use fuzzy assessment method to get the

He Song-bai; Wei Ai-guo; Yu Dian-xiang; Tan Zhong; Wang Peng

2009-01-01

448

Size-Distribution Analysis of Macromolecules by Sedimentation Velocity Ultracentrifugation and Lamm Equation Modeling  

Microsoft Academic Search

A new method for the size-distribution analysis of polymers by sedimentation velocity analytical ultracentrifugation is described. It exploits the ability of Lamm equation modeling to discriminate between the spreading of the sedimentation boundary arising from sample heterogeneity and from diffusion. Finite element solutions of the Lamm equation for a large number of discrete noninteracting species are combined with maximum entropy

Peter Schuck

2000-01-01

449

Combining microsimulation with CGE and macro modelling for distributional analysis in developing and transition countries  

Microsoft Academic Search

This paper overviews recent work that has attempted to bring together microsimulation, Computable General Equilibrium (CGE) and macro models to perform distributional analysis in developing and transition countries. Particular attention is paid to applications relating to aspects of economic growth and political economy. Applications in which macro, CGE and microsimulation models are either layered or integrated are considered. It is

James B Davies

2009-01-01

450

The Locational Distribution of Foreign Banks in China: A Disaggregated Analysis  

Microsoft Academic Search

He C. and Yeung G. The locational distribution of foreign banks in China: a disaggregated analysis, Regional Studies. This paper examines the location choices made by foreign banks of different organizational form and size in China. Results from the conditional logit models suggest smaller foreign banks tend to pursue the ‘follow-the-customer’ strategy, while larger banks are likely to use the

Canfei He; Godfrey Yeung

2011-01-01

451

Analysis of Passive Optical Networks for Subcarrier Multiplexed Quantum Key Distribution  

Microsoft Academic Search

This paper provides an analysis of the performance of different passive optical network (PON) topologies for the distribution of multiuser quantum keys using subcarrier multiplexing and the Bennet-Brassard (BB84) protocol. PON topologies are evaluated in terms of the achievable quantum bit error rate (QBER) and the useful key rate. Results show that wavelength routed (WR) networks outperform broadcast topologies as

José Capmany; Carlos R. Fernández-Pousa

2010-01-01

452

Image Analysis Method (IAM) for Measurement of Particle Size Distribution and Mass Availability on Carpet Fibers  

Microsoft Academic Search

Exposure to particles that have deposited on surfaces is common in occupational and residential environments. Lack of an accurate tool for assessing particle size distribution and loading (mass per unit area) on carpet fibers available for exposure contributes to the uncertainty associated with current risk assessment models. This research presents a new, direct image analysis method (IAM) for measuring particle

Jonathan Thornburg; Charles Rodes; Michael Lamvik; Robert Willis; Jacky Rosati

2006-01-01

453

Modeling call holding time distributions for CCS network design and performance analysis  

Microsoft Academic Search

The message traffic offered to the CCS signalling network depends on and is modulated by the traffic characteristics of the circuit switched calls supported by the CCS network. Most previous analyses of CCS network engineering, performance evaluation and congestion control protocols generally assume an exponential holding time of circuit switched calls. Analysis of actual holding time distributions in conversations, facsimile

Vladimir A. Bolotin

1994-01-01

454

Regional Distribution of Consultancy Firms Servicing the MAPCON Scheme: A Preliminary Analysis  

Microsoft Academic Search

VINCENT P., CHELL E. and HAWORTH J. (1987) Regional distribution of consultancy firms servicing the MAPCON scheme: a preliminary analysis, Reg. Studies21, 505–518. This paper examines published data pertaining to the MAPCON scheme which is one of a number of government schemes aimed at the revival of British industry. The paper outlines the argument regarding the role of information in

Peter Vincent; Elizabeth Chell; Jean Haworth

1987-01-01

455

Infrared thermoimage analysis as real time technique to evaluate in-field pesticide spraying quality distribution  

NASA Astrophysics Data System (ADS)

Tests and calibration of sprayers have been considered a very important task for chemicals use reduction in agriculture and for improvement of plant phytosanitary protection. A reliable, affordable and easy-to-use method to observe the distribution in the field is required and the infrared thermoimage analysis can be considered as a potential method based on non-contact imaging technologies. The basic idea is that the application of colder water (10 °C less) than the leaves surface makes it possible to distinguish and measure the targeted areas by means of a infrared thermoimage analysis based on significant and time persistent thermal differences. Trials were carried out on a hedge of Prunus laurocerasus, 2.1 m height with an homogenous canopy. A trailed orchard sprayer was employed with different spraying configurations. A FLIRTM (S40) thermocamera was used to acquire (@ 50 Hz) thermal videos, in a fixed position, at frame rate of 10 images/s, for nearly 3 min. Distribution quality was compared to the temperature differences obtained from the thermal images between pre-treatment and post-treatment (?T)., according two analysis: time-trend of ?T average values for different hedge heights and imaging ?T distribution and area coverage by segmentation in k means clustering after 30 s of spraying. The chosen spraying configuration presented a quite good distribution for the entire hedge height with the exclusion of the lower (0-1 m from the ground) and the upper part (>1.9 m). Through the image segmentation performed of ?T image by k-means clustering, it was possible to have a more detailed and visual appreciation of the distribution quality among the entire hedge. The thermoimage analysis revealed interesting potentiality to evaluate quality distribution from orchards sprayers.

Menesatti, P.; Biocca, M.

2007-09-01

456

Efficient, Distributed and Interactive Neuroimaging Data Analysis Using the LONI Pipeline.  

PubMed

The LONI Pipeline is a graphical environment for construction, validation and execution of advanced neuroimaging data analysis protocols (Rex et al., 2003). It enables automated data format conversion, allows Grid utilization, facilitates data provenance, and provides a significant library of computational tools. There are two main advantages of the LONI Pipeline over other graphical analysis workflow architectures. It is built as a distributed Grid computing environment and permits efficient tool integration, protocol validation and broad resource distribution. To integrate existing data and computational tools within the LONI Pipeline environment, no modification of the resources themselves is required. The LONI Pipeline provides several types of process submissions based on the underlying server hardware infrastructure. Only workflow instructions and references to data, executable scripts and binary instructions are stored within the LONI Pipeline environment. This makes it portable, computationally efficient, distributed and independent of the individual binary processes involved in pipeline data-analysis workflows. We have expanded the LONI Pipeline (V.4.2) to include server-to-server (peer-to-peer) communication and a 3-tier failover infrastructure (Grid hardware, Sun Grid Engine/Distributed Resource Management Application API middleware, and the Pipeline server). Additionally, the LONI Pipeline provides three layers of background-server executions for all users/sites/systems. These new LONI Pipeline features facilitate resource-interoperability, decentralized computing, construction and validation of efficient and robust neuroimaging data-analysis workflows. Using brain imaging data from the Alzheimer's Disease Neuroimaging Initiative (Mueller et al., 2005), we demonstrate integration of disparate resources, graphical construction of complex neuroimaging analysis protocols and distributed parallel computing. The LONI Pipeline, its features, specifications, documentation and usage are available online (http://Pipeline.loni.ucla.edu). PMID:19649168

Dinov, Ivo D; Van Horn, John D; Lozev, Kamen M; Magsipoc, Rico; Petrosyan, Petros; Liu, Zhizhong; Mackenzie-Graham, Allan; Eggert, Paul; Parker, Douglas S; Toga, Arthur W

2009-07-20

457

Strength Improvement on an Imaginary SiC Fiber of Ideal Diameter and Reduced Internal Defects Estimated from the Weibull Scaling of Tyranno ZMI Fiber  

Microsoft Academic Search

The size effect of the diameter has been assessed for the tensile strength of Tyranno ZMI fiber. Uniform diameter section in sample fibers has been selected as tensile test sample. The single fibers of measured diameters have been tensile tested to provide two groups of data, i.e., ``small diameter'' group and ``large diameter'' group. The parameters of single-modal Weibull model

Tetsuya Morimoto; Koji Yamamoto; Shinji Ogihara

2006-01-01

458

Critical analysis of condition-survey techniques for gas distribution systems  

SciTech Connect

Comparing the US gas distribution system's physical characteristics, failure modes, and operating conditions, IGT engineers identified six promising nondestructive testing methods for determining the condition of in-place piping systems: (1) magnetic field/eddy current; (2) ultrasonic; (3) backscatter radiation; (4) acoustic leak detection; (5) acoustic emission analysis; and (6) vibrational analysis. By supplementing NDT data with statistical and analytical techniques, utilities can quantify current pipe conditions and predict the probability of failure. A subjective economic analysis indicated no distinct cost advantage among the six techniques.

Johnson, D.; Huebler, J.E.; Craig, J.M.; Landahl, C.

1981-02-01

459

Statistical analysis of the genomic distribution and correlation of regulatory elements in the ENCODE regions  

PubMed Central

The comprehensive inventory of functional elements in 44 human genomic regions carried out by the ENCODE Project Consortium enables for the first time a global analysis of the genomic distribution of transcriptional regulatory elements. In this study we developed an intuitive and yet powerful approach to analyze the distribution of regulatory elements found in many different ChIP–chip experiments on a 10?100-kb scale. First, we focus on the overall chromosomal distribution of regulatory elements in the ENCODE regions and show that it is highly nonuniform. We demonstrate, in fact, that regulatory elements are associated with the location of known genes. Further examination on a local, single-gene scale shows an enrichment of regulatory elements near both transcription start and end sites. Our results indicate that overall these elements are clustered into regulatory rich “islands” and poor “deserts.” Next, we examine how consistent the nonuniform distribution is between different transcription factors. We perform on all the factors a multivariate analysis in the framework of a biplot, which enhances biological signals in the experiments. This groups transcription factors into sequence-specific and sequence-nonspecific clusters. Moreover, with experimental variation carefully controlled, detailed correlations show that the distribution of sites was generally reproducible for a specific factor between different laboratories and microarray platforms. Data sets associated with histone modifications have particularly strong correlations. Finally, we show how the correlations between factors change when only regulatory elements far from the transcription start sites are considered.

Zhang, Zhengdong D.; Paccanaro, Alberto; Fu, Yutao; Weissman, Sherman; Weng, Zhiping; Chang, Joseph; Snyder, Michael; Gerstein, Mark B.

2007-01-01

460

Joint distribution of successive wave steepness parameters. [Water wave modeling and effects on offshore oil platforms  

Microsoft Academic Search

In this paper, a joint distribution of wave steepness parameters for two successive waves is presented. The wave steepness parameters considered herein are the crest front steepness and the total wave steepness. The joint distribution of wave steepness parameters for two successive waves is represented by a two-dimensional Weibull distribution with the parameters [alpha]=0.84 and [beta]=1.40. The application of the

D. Myrhaug; H. Rue

1993-01-01

461

Particle size distributions and the sequential fragmentation\\/transport theory applied to volcanic ash  

Microsoft Academic Search

The assumption that distributions of mass versus size interval for fragmented materials fit the log normal distribution is empirically based and has historical roots in the late 19th century. Other often used distributions (e.g., Rosin-Rammler, Weibull) are also empirical and have the general form for mass per size interval: n(l)=klalpha exp(-lbeta), where n(l) represents the number of particles of diameter

K. H. Wohletz; M. F. Sheridan; W. K. Brown

1989-01-01

462

Three-dimensional modeling and quantitative analysis of gap junction distributions in cardiac tissue.  

PubMed

Gap junctions play a fundamental role in intercellular communication in cardiac tissue. Various types of heart disease including hypertrophy and ischemia are associated with alterations of the spatial arrangement of gap junctions. Previous studies applied two-dimensional optical and electron-microscopy to visualize gap junction arrangements. In normal cardiomyocytes, gap junctions were primarily found at cell ends, but can be found also in more central regions. In this study, we extended these approaches toward three-dimensional reconstruction of gap junction distributions based on high-resolution scanning confocal microscopy and image processing. We developed methods for quantitative characterization of gap junction distributions based on analysis of intensity profiles along the principal axes of myocytes. The analyses characterized gap junction polarization at cell ends and higher-order statistical image moments of intensity profiles. The methodology was tested in rat ventricular myocardium. Our analysis yielded novel quantitative data on gap junction distributions. In particular, the analysis demonstrated that the distributions exhibit significant variability with respect to polarization, skewness, and kurtosis. We suggest that this methodology provides a quantitative alternative to current approaches based on visual inspection, with applications in particular in characterization of engineered and diseased myocardium. Furthermore, we propose that these data provide improved input for computational modeling of cardiac conduction. PMID:21822740

Lackey, Daniel P; Carruth, Eric D; Lasher, Richard A; Boenisch, Jan; Sachse, Frank B; Hitchcock, Robert W

2011-08-06

463

Phosphorescence lifetime analysis with a quadratic programming algorithm for determining quencher distributions in heterogeneous systems.  

PubMed Central

A new method for analysis of phosphorescence lifetime distributions in heterogeneous systems has been developed. This method is based on decomposition of the data vector to a linearly independent set of exponentials and uses quadratic programming principles for x2 minimization. Solution of the resulting algorithm requires a finite number of calculations (it is not iterative) and is computationally fast and robust. The algorithm has been tested on various simulated decays and for analysis of phosphorescence measurements of experimental systems with descrete distributions of lifetimes. Critical analysis of the effect of signal-to-noise on the resolving capability of the algorithm is presented. This technique is recommended for resolution of the distributions of quencher concentration in heterogeneous samples, of which oxygen distributions in tissue is an important example. Phosphors of practical importance for biological oxygen measurements: Pd-meso-tetra (4-carboxyphenyl) porphyrin (PdTCPP) and Pd-meso-porphyrin (PdMP) have been used to provide experimental test of the algorithm.

Vinogradov, S A; Wilson, D F

1994-01-01

464

Comparison of Photon Correlation Spectroscopy With Photosedimentation Analysis for the Determination of Aqueous Colloid Size Distributions  

NASA Astrophysics Data System (ADS)

Colloidal materials, dispersed phases with dimensions between 0.001 and 1 ?m, are potential transport media for a variety of contaminants in surface and ground water. Characterization of these colloids, and identification of the parameters that control their movement, are necessary before transport simulations can be attempted. Two techniques that can be used to determine the particle-size distribution of colloidal materials suspended in natural waters are compared. Photon correlation Spectroscopy (PCS) utilizes the Doppler frequency shift of photons scattered off particles undergoing Brownian motion to determine the size of colloids suspended in water. Photosedimentation analysis (PSA) measures the time-dependent change in optical density of a suspension of colloidal particles undergoing centrifugation. A description of both techniques, important underlying assumptions, and limitations are given. Results for a series of river water samples show that the colloid-size distribution means are statistically identical as determined by both techniques. This also is true of the mass median diameter (MMD), even though MMD values determined by PSA are consistently smaller than those determined by PCS. Because of this small negative bias, the skew parameters for the distributions are generally smaller for the PCS-determined distributions than for the PSA-determined distributions. Smaller polydispersity indices for the distributions are also determined by PCS.

Rees, Terry F.

1990-11-01

465

Distributed hot-wire anemometry based on Brillouin optical time-domain analysis.  

PubMed

A distributed hot-wire anemometer based on Brillouin optical time-domain analysis is presented. The anemometer is created by passing a current through a stainless steel tube fibre bundle and monitoring Brillouin frequency changes in the presence of airflow. A wind tunnel is used to provide laminar airflow while the device response is calibrated against theoretical models. The sensitivity equation for this anemometer is derived and discussed. Airspeeds from 0 m/s to 10 m/s are examined, and the results show that a Brillouin scattering based distributed hot-wire anemometer is feasible. PMID:22772259

Wylie, Michael T V; Brown, Anthony W; Colpitts, Bruce G

2012-07-01

466

Comparison of susceptibility to pitting corrosion of AA2024-T4, AA7075-T651 and AA7475-T761 aluminium alloys in neutral chloride solutions using electrochemical noise analysis  

Microsoft Academic Search

The susceptibility to pitting corrosion of AA2024-T4, AA7075-T651 and AA7475-T761 aluminium alloys was investigated in aqueous neutral chloride solution for the purpose of comparison using electrochemical noise measurement. The experimentally measured electrochemical noises were analysed based upon the combined stochastic theory and shot-noise theory using the Weibull distribution function. From the occurrence of two linear regions on one Weibull probability

Kyung-Hwan Na; Su-Il Pyun

2008-01-01

467

Three-parameter discontinuous distributions for hydrological samples with zero values  

NASA Astrophysics Data System (ADS)

A consistent approach to the frequency analysis of hydrologic data in arid and semiarid regions, i.e. the data series containing several zero values (e.g. monthly precipitation in dry seasons, annual peak flow discharges, etc.), requires using discontinuous probability distribution functions. Such an approach has received relatively limited attention. Along the lines of physically based models, the extensions of the Muskingum-based models to three parameter forms are considered. Using 44 peak flow series from the USGS data bank, the fitting ability of four three-parameter models was investigated: (1) the Dirac delta combined with Gamma distribution; (2) the Dirac delta combined with two-parameter generalized Pareto distribution; (3) the Dirac delta combined with two-parameter Weibull (DWe) distribution; (4) the kinematic diffusion with one additional parameter that controls the probability of the zero event (KD3). The goodness of fit of the models was assessed and compared both by evaluation of discrepancies between the results of both estimation methods (i.e. the method of moments (MOM) and the maximum likelihood method (MLM)) and using the log of likelihood function as a criterion. In most cases, the DWe distribution with MLM-estimated parameters showed the best fit of all the three-parameter models.

Weglarczyk, Stanislaw; Strupczewski, Witold G.; Singh, Vijay P.

2005-10-01

468

A Real-Time Line Reclosing Analysis Technique Analysis Using Distribution Factors  

Microsoft Academic Search

This paper describes a recently developed real-time computer program at the control center of the Pennsylvania-New Jersey-Maryland Inter- connection (PJM) designed to determine the impact of returning a transmission facility to service. The method is unique in that it incorporates the use of only megawatt flows and distribution factors. The paper discusses the solution algorithm and the applicability of its

H. H. Yan; J. D. Willson

1980-01-01

469

Estimating plant responses to climate by direct gradient analysis and geographic distribution analysis  

Microsoft Academic Search

We characterised the climatic behaviour of 53 woody species in terms of the climatic factors that play the main role in controlling\\u000a species distribution in the study area. Floristic and climatic data were obtained from 150 stands in sites under climatic\\u000a control (i.e. eu-climatopes). The sampling strategy used allowed a reliable match between floristic and climatic observations.\\u000a Different methods of

Rubén Retuerto; Alejo Carballeira

2004-01-01

470

Analysis and evaluation of planned and delivered dose distributions: practical concerns with ?- and ?- Evaluations  

NASA Astrophysics Data System (ADS)

One component of clinical treatment validation, for example in the commissioning of new radiotherapy techniques or in patient specific quality assurance, is the evaluation and verification of planned and delivered dose distributions. Gamma and related tests (such as the chi evaluation) have become standard clinical tools for such work. Both functions provide quantitative comparisons between dose distributions, combining dose difference and distance to agreement criteria. However, there are some practical considerations in their utilization that can compromise the integrity of the tests, and these are occasionally overlooked especially when the tests are too readily adopted from commercial software. In this paper we review the evaluation tools and describe some practical concerns. The intent is to provide users with some guidance so that their use of these evaluations will provide valid rapid analysis and visualization of the agreement between planned and delivered dose distributions.

Schreiner, L. J.; Holmes, O.; Salomons, G.

2013-06-01

471

Phenomenological analysis of fluctuations in the lateral distribution of shower particles  

SciTech Connect

The fluctuations in the lateral distribution of EAS electrons measured by a detector of finite size are analyzed phenomenologically. With the simplest assumptions about the statistical characteristics of the random distribution of particles in the observation plane, it is possible to solve the problem using the mean cascade curves, the relative fluctuations of the total number of particles, and the mean lateral distributions. It is shown that the square of the relative fluctuations of the number of particles hitting a fixed area {sigma}{sub {ital k}} can be written as the sum of two terms, the first tending to a finite limit and the second behaving as {sigma}{sup {minus}1}{sub {ital k}} for {sigma}{sub {ital k}}{r arrow}0. The results of the analysis are confirmed by numerical calculations.

Uchaikin, V.V.; Chernyaev, G.V. (Altai State University (SU))

1989-09-01

472

[Analysis of streamer properties and emission spectroscopy of 2-D OH distribution of pulsed corona discharge].  

PubMed

Streamer plays a key role in the process of OH radical generation. The propagation of primary and secondary streamers of positive wire-plate pulsed corona discharge was observed using a short gate ICCD in air environment. The influence of the applied voltage on the properties was investigated. It was shown that the primary streamer propagation velocity, electric coverage and length of secondary streamer increased significantly with increasing the applied voltage. Then 2-D OH distribution was investigated by the emission spectrum. With the analysis of the OH emission spectra, the distribution of OH radicals showed a trend of decreasing from the wire electrode to its circumambience. Compared with the streamer propagation trace, the authors found that OH radical distribution and streamer are in the same area. Both OH radical concentration and the intensity of streamer decreased when far away from the wire electrode. PMID:22242481

Zhao, Lei; Gao, Xiang; Luo, Zhong-Yang; Xuan, Jian-Yong; Jiang, Jian-Ping; Cen, Ke-Fa

2011-11-01

473

Image analysis and bending properties of model OSB panels as a function of strand distribution, shape and size  

Microsoft Academic Search

The technique of image analysis has been used to assess the quality of model oriented strand board panels by investigating the relationships between shape and size of strands, the distribution of strands and bending properties. A batch of commercial strands was analysed by image analysis and the distribution of the shape and size of strands was quantified. The strands were

Takuya Nishimura; Jaymeen Amin; Martin P. Ansell

2004-01-01

474

Adhesively bonded joints composed of pultruded adherends: Considerations at the upper tail of the material strength statistical distribution  

Microsoft Academic Search

The Weibull distribution, used to describe the scaling of strength of materials, has been verified on a wide range of materials and geometries; however, the quality of the fitting tended to be less good towards the upper tail. Based on a previously developed probabilistic strength prediction method for adhesively bonded joints composed of pultruded glass fiber-reinforced polymer (GFRP) adherends, where

Till Vallée; Thomas Keller; Gilles Fourestey; Benjamin Fournier; João R. Correia

2009-01-01

475

Analysis of spatial distribution of mining tremors occurring in Rudna copper mine (Poland)  

NASA Astrophysics Data System (ADS)

The distribution of mining tremors is strictly related to the exploitation progress of mining works and, consequently, to the local stress field. In case the distribution is known, it is possible to determine future area of intensive seismicity in exploited mining panel. In the paper, an analysis of working face-to-tremor distance for Rudna copper mine in Poland is presented. In order to develop a spatial model of tremors' occurrence in the exploited mine, the seismicity of four mining sections in the five-month period was investigated and the tremors' distribution was obtained. It was compared with the spatial distribution of tremors in coal mines found in the literature. The results show that the places where tremors mostly occur — the vicinity of the face, in front of it — coincide with the high-stress area predicted by literature models. The obtained results help to predict the future seismic zone connected with planned mining section, which can be used in seismic hazard analysis.

Koz?owska, Maria

2013-10-01

476

Stress distribution around osseointegrated implants with different internal-cone connections: photoelastic and finite element analysis.  

PubMed

Abstract The goal of this study was to evaluate the distribution of stresses generated around implants with different internal-cone abutments by photoelastic (PA) and finite element analysis (FEA). For FEA, implant and abutments with different internal-cone connections (H- hexagonal and S- solid) were scanned, 3D meshes were modeled and objects were loaded with computer software. Trabecular and cortical bones and photoelastic resin blocks were simulated. The PA was performed with photoelastic resin blocks where implants were included and different abutments were bolted. Specimens were observed in the circular polariscope with the application device attached, where loads were applied on same conditions as FEA. FEA images showed very similar stress distribution between two models with different abutments. Differences were observed between stress distribution in bone and resin blocks; PA images resembled those obtained on resin block FEA. PA images were also quantitatively analyzed by comparing the values assigned to fringes. It was observed that S abutment distributes loads more evenly to bone adjacent to an implant when compared to H abutment, for both analysis methods used. It was observed that the PA has generated very similar results to those obtained in FEA with the resin block. PMID:23750560

Anami, Lilian; Costa Lima, Júlia; Takahashi, Fernando; Neisser, Maximiliano; Noritomi, Pedro; Bottino, Marco Antonio

2013-06-10

477

First results and analysis of collective Thomson scattering (CTS) fast ion distribution measurements on ASDEX Upgrade  

NASA Astrophysics Data System (ADS)

Experimental knowledge of the fast ion physics in magnetically confined plasmas is essential. The collective Thomson scattering (CTS) diagnostic is capable of measuring localized 1D ion velocity distributions and anisotropies dependent on the angle to the magnetic field. The CTS installed at ASDEX-Upgrade (AUG) uses mm-waves generated by the 1 MW dual frequency gyrotron. The successful commissioning the CTS at AUG enabled first scattering experiments and the consequent milestone of first fast ion distribution measurements on AUG presented in this paper. The first fast ion distribution results have already uncovered some physics of confined fast ions at the plasma centre with off-axis neutral beam heating. However, CTS experiments on AUG H-mode plasmas have also uncovered some unexpected signals not related to scattering that required additional analysis and treatment of the data. These secondary emission signals are generated from the plasma-gyrotron interaction therefore contain additional physics. Despite their existence that complicate the fast ion analysis, they do not prevent the diagnostic's capability to infer the fast ion distribution function on AUG.

Meo, F.; Stejner, M.; Salewski, M.; Bindslev, H.; Eich, T.; Furtula, V.; Korsholm, S. B.; Leuterer, F.; Leipold, F.; Michelsen, P. K.; Moseev, D.; Nielsen, S. K.; Reiter, B.; Stober, J.; Wagner, D.; Woskov, P.; ASDEX Upgrade Team

2010-05-01

478

Passive-scheme analysis for solving the untrusted source problem in quantum key distribution  

SciTech Connect

As a practical method, the passive scheme is useful to monitor the photon statistics of an untrusted source in a 'Plug and Play' quantum key distribution (QKD) system. In a passive scheme, three kinds of monitor mode can be adopted: average photon number (APN) monitor, photon number analyzer (PNA), and photon number distribution (PND) monitor. In this paper, the security analysis is rigorously given for the APN monitor, while for the PNA, the analysis, including statistical fluctuation and random noise, is addressed with a confidence level. The results show that the PNA can achieve better performance than the APN monitor and can asymptotically approach the theoretical limit of the PND monitor. Also, the passive scheme with the PNA works efficiently when the signal-to-noise ratio (R{sup SN}) is not too low and so is highly applicable to solve the untrusted source problem in the QKD system.

Peng Xiang; Xu Bingjie; Guo Hong [CREAM Group, State Key Laboratory of Advanced Optical Communication Systems and Networks (Peking University) and Institute of Quantum Electronics, School of Electronics Engineering and Computer Science, Peking University, Beijing 100871 (China)

2010-04-15

479

Passive-scheme analysis for solving the untrusted source problem in quantum key distribution  

NASA Astrophysics Data System (ADS)

As a practical method, the passive scheme is useful to monitor the photon statistics of an untrusted source in a “Plug & Play” quantum key distribution (QKD) system. In a passive scheme, three kinds of monitor mode can be adopted: average photon number (APN) monitor, photon number analyzer (PNA), and photon number distribution (PND) monitor. In this paper, the security analysis is rigorously given for the APN monitor, while for the PNA, the analysis, including statistical fluctuation and random noise, is addressed with a confidence level. The results show that the PNA can achieve better performance than the APN monitor and can asymptotically approach the theoretical limit of the PND monitor. Also, the passive scheme with the PNA works efficiently when the signal-to-noise ratio (RSN) is not too low and so is highly applicable to solve the untrusted source problem in the QKD system.

Peng, Xiang; Xu, Bingjie; Guo, Hong

2010-04-01

480

Nuclear micro-beam analysis of deuterium distribution in carbon fibre composites for controlled fusion devices  

NASA Astrophysics Data System (ADS)

Probes made of carbon fibre composite NB41 were exposed to deuterium plasmas in the TEXTOR tokamak and in a simulator of plasma-wall interactions, PISCES. The aim was to assess the deuterium retention and its lateral and depth distribution. The analysis was performed by means of D(3He, p)4He and 12C(3He, p)14N nuclear reactions analysis using a standard (1 mm spot) and micro-beam (20 ?m resolution). The measurements have revealed non uniform distribution of deuterium atoms in micro-regions: differences by a factor of 3 between the maximum and minimum deuterium concentrations. The differences were associated with the orientation and type of fibres for samples exposed in PICSES. For surface structure in the erosion zone of samples exposed to a tokamak plasma the micro-regions were more complex. Depth profiling has indicated migration of fuel into the bulk of materials.

Petersson, P.; Kreter, A.; Possnert, G.; Rubel, M.

2010-06-01

481

Risk analysis of highly combustible gas storage, supply, and distribution systems in PWR plants  

SciTech Connect

This report presents the evaluation of the potential safety concerns for pressurized water reactors (PWRs) identified in Generic Safety Issue 106, Piping and the Use of Highly Combustible Gases in Vital Areas. A Westinghouse four-loop PWR plant was analyzed for the risk due to the use of combustible gases (predominantly hydrogen) within the plant. The analysis evaluated an actual hydrogen distribution configuration and conducted several sensitivity studies to determine the potential variability among PWRs. The sensitivity studies were based on hydrogen and safety-related equipment configurations observed at other PWRs within the United States. Several options for improving the hydrogen distribution system design were identified and evaluated for their effect on risk and core damage frequency. A cost/benefit analysis was performed to determine whether alternatives considered were justifiable based on the safety improvement and economics of each possible improvement.

Simion, G.P. [Science Applications International Corp., Albuquerque, NM (United States); VanHorn, R.L.; Smith, C.L.; Bickel, J.H.; Sattison, M.B. [EG and G Idaho, Inc., Idaho Falls, ID (United States); Bulmahn, K.D. [SCIENTECH, Inc., Idaho Falls, ID (United States)

1993-06-01

482

Generalized extreme value distribution fitted by LH moments for low-flow frequency analysis  

NASA Astrophysics Data System (ADS)

This study introduces a method based on LH moments to use the generalized extreme value (GEV) distribution for low-flow frequency analysis and investigates the capability of the GEV distribution fitted by LH moments to effectively model the lower tail of the low-flow frequency curve, without explicitly censoring the data sample. The performance of the GEV/L moment (the GEV distribution fitted by L moments) and GEV/LH moment (the GEV distribution fitted by LH moments) methods are assessed by evaluating the bias, mean square error, and relative accuracy of quantile estimates through Monte Carlo simulations. It is shown that when both frequent low flows and extreme low flows can be adequately described by an assumed parent distribution, both GEV/L2 moment and GEV/L moment methods make equally accurate quantile estimates. However, when frequent low flows and extreme low flows do not follow a single trend, the bias of the GEV/L2 moment estimator is negligible, while the bias of the GEV/L moment estimator is significant at large annual recurrence intervals. On average, the GEV/L2 moment quantile estimator displays less bias than the GEV/L moment quantile estimator. Furthermore, as the annual recurrence interval increases, the relative accuracy of the GEV/L2 moment method consistently improves over the GEV/L moment method. The GEV/LH moment method is thus considered to be the more suitable method to model low flows.

Hewa, G. A.; Wang, Q. J.; McMahon, T. A.; Nathan, R. J.; Peel, M. C.

2007-06-01

483

Parallel On-Chip Power Distribution Network Analysis on Multi-Core-Multi-GPU Platforms  

Microsoft Academic Search

The challenging task of analyzing on-chip power (ground) distribution networks with multimillion node complexity and beyond is key to today's large chip designs. For the first time, we show how to exploit recent massively parallel single-in- struction multiple-thread (SIMT)-based graphics processing unit (GPU) platforms to tackle large-scale power grid analysis with promising performance. Several key enablers including GPU-specific algorithm design,

Zhuo Feng; Zhiyu Zeng; Peng Li

2011-01-01

484

Reduction-based schedulability analysis of distributed systems with cycles in the task graph  

Microsoft Academic Search

A significant problem with no simple solutions in current real-time literature is analyzing the end-to-end schedulability\\u000a of tasks in distributed systems with cycles in the task graph. Prior approaches including network calculus and holistic schedulability\\u000a analysis work best for acyclic task flows. They involve iterative solutions or offer no solutions at all when flows are non-acyclic.\\u000a This paper demonstrates the

Praveen Jayachandran; Tarek F. Abdelzaher

2010-01-01