Analysis of interval-censored data with Weibull lifetime distribution
Kundu, Debasis
Analysis of interval-censored data with Weibull lifetime distribution Biswabrata Pradhan & Debasis Kundu Abstract In this work the analysis of interval-censored data, with Weibull distribution to investigate the finite sam- ple performance of the proposed estimators, and the analysis of two data sets; one
Weibull Failure Distribution Analysis and Plotting System. Computer code manual
Fatula, J.F.
1984-10-01
This report describes the Weibull Failure Distribution Analysis and Plotting System, an interactive computer program for the estimation and plotting of Weibull time-to-failure models for sample data. The report discusses use of the system, estimation methodology, and implementation details. Described are the principal elements of the source code. The program is available under license from the ERPRI Electric Power Software Center.
Weibull Failure Distribution Analysis and Plotting System. Computer code manual
Fatula
1984-01-01
This report describes the Weibull Failure Distribution Analysis and Plotting System, an interactive computer program for the estimation and plotting of Weibull time-to-failure models for sample data. The report discusses use of the system, estimation methodology, and implementation details. Described are the principal elements of the source code. The program is available under license from the ERPRI Electric Power Software
/q-exponential, Weibull, and /q-Weibull distributions: an empirical analysis
NASA Astrophysics Data System (ADS)
Picoli, S.; Mendes, R. S.; Malacarne, L. C.
2003-06-01
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.
A general linear-regression analysis applied to the 3-parameter Weibull distribution
Yong-Ming Li; Reader Aids
1994-01-01
The conventional techniques of linear regression analysis (linear least squares) applied to the 3-parameter Weibull distribution are extended (not modified), and new techniques are developed for the 3-parameter Weibull distribution. The three pragmatic estimation methods in this paper are simple, accurate, flexible, and powerful in dealing with difficult problems such as estimates of the 3 parameters becoming nonpositive. In addition,
On Hybrid Censored Weibull Distribution Debasis Kundu
Kundu, Debasis
concern is, the analysis becomes too difficult and may not be tractable. Weibull distribution is oneOn Hybrid Censored Weibull Distribution Debasis Kundu Abstract A hybrid censoring is a mixture of Type-I and Type-II censoring schemes. This arti- cle presents the statistical inferences on Weibull
Using Weibull Distribution Analysis to Evaluate ALARA Performance
E. L. Frome, J. P. Watkins, and D. A. Hagemeyer
2009-10-01
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.
Reliability analysis of structural ceramic components using a three-parameter Weibull distribution
Duffy, S.F.; Powers, L.M.; Starlinger, A. (Cleveland State Univ., OH (United States) NASA, Lewis Research Center, Cleveland, OH (United States))
1992-01-01
Described here are nonlinear regression estimators for the three-parameter Weibull distribution. Issues relating to the bias and invariance associated with these estimators are examined numerically using Monte Carlo simulation methods. The estimators were used to extract parameters from sintered silicon nitride failure data. A reliability analysis was performed on a turbopump blade utilizing the three-parameter Weibull distribution and the estimates from the sintered silicon nitride data. 16 refs.
Reliability analysis of structural ceramic components using a three-parameter Weibull distribution
NASA Technical Reports Server (NTRS)
Duffy, Stephen F.; Powers, Lynn M.; Starlinger, Alois
1992-01-01
Described here are nonlinear regression estimators for the three-Weibull distribution. Issues relating to the bias and invariance associated with these estimators are examined numerically using Monte Carlo simulation methods. The estimators were used to extract parameters from sintered silicon nitride failure data. A reliability analysis was performed on a turbopump blade utilizing the three-parameter Weibull distribution and the estimates from the sintered silicon nitride data.
Reliability analysis of structural ceramic components using a three-parameter Weibull distribution
NASA Technical Reports Server (NTRS)
Duffy, Stephen F.; Powers, Lynn M.; Starlinger, Alois
1992-01-01
Described here are nonlinear regression estimators for the three-parameter Weibull distribution. Issues relating to the bias and invariance associated with these estimators are examined numerically using Monte Carlo simulation methods. The estimators were used to extract parameters from sintered silicon nitride failure data. A reliability analysis was performed on a turbopump blade utilizing the three-parameter Weibull distribution and the estimates from the sintered silicon nitride data.
Applicability of Weibull analysis for brittle materials
K. Trustrum; A. De S. Jayatilaka
1983-01-01
Weibull analysis for the interpretation of strengths of brittle materials was previously justified for a particular flaw size distribution. The present results show that the Weibull distribution provides a close approximation to the distribution of failure stress for all the flaw size distributions considered. However certain reservations are noted in the interpretation of the Weibull modulus.
Estimation of P[Y Weibull Distribution
Kundu, Debasis
Estimation of P[Y Weibull Distribution Debasis Kundu1 Rameshwar D. Gupta2 Abstract This paper deals with the estimation of R = P[Y Weibull distributions the different proposed methods. Analysis of a real data set has also been presented for illustrative purposes
The Weibull distribution applied to regional low flow frequency analysis
P. J. PILON
1990-01-01
The inability to estimate accurately low flows of specific duration and probability for ungauged basins has long plagued the practitioner. The index-flood method is one tool which may assist in this regard, through its adaptation to low flows. This paper outlines the extension of the index-flood method to low flow analysis when the regional distribution is assumed to be the
Bayes Estimation for the Marshall-Olkin Bivariate Weibull Distribution
Kundu, Debasis
. Gupta2 Abstract In this paper, we consider the Bayesian analysis of the Marshall-Olkin bivariate WeibullBayes Estimation for the Marshall-Olkin Bivariate Weibull Distribution Debasis Kundu1 & Arjun K distribution. It is a singular distribution whose marginals are Weibull dis- tributions
A new algorithm for mixed Weibull analysis of partial discharge amplitude distributions
R. Schifani; R. Candela
1999-01-01
In this paper, an heuristic algorithm is presented for the evaluation of the parameters of additive-Weibull distributions having more than two elementary functions, which is a necessary condition when testing complex insulating structures with different partial discharge (PD) sources. The algorithm has, in principle, no limit in the number of component Weibull functions. Furthermore, it should be emphasized that it
Y. Wang; Y. C. Chan; Z. L. Gui; D. P. Webb; L. T. Li
1997-01-01
The Weibull distribution has been previously applied to the mechanical and dielectric failures of ceramics. In this paper, it is confirmed by experiment that this data treatment method is also valid for application in the dielectric failure of multilayer ceramic capacitors (MLCs) which have undergone screening. The Weibull modulus is found to be a useful parameter indicating the sharpness of
NASA Technical Reports Server (NTRS)
Park, Won J.; Crampton, George H.
1988-01-01
The suitability of the two-parameter Weibull distribution for describing highly censored cat motion sickness latency data was evaluated by estimating the parameters with the maximum likelihood method and testing for goodness of fit with the Kolmogorov-Smirnov statistic. A procedure for determining confidence levels and testing for significance of the difference between Weibull parameters is described. Computer programs for these procedures may be obtained from an archival source.
The Weibull - Log Weibull Distribution for Inter-occurrence Times of Earthquakes
Hasumi, Tomohiro; Aizawa, Yoji
2008-01-01
Analyzing the JMA seismic catalog for different tectonic setting regions, we have revealed that the probability distributions of time intervals between successive earthquakes, inter-occurrence times, can be described by the superposition of the Weibull distribution and log Weibull one. For large earthquakes the distribution obeys the Weibull distribution with the exponent less than 1. It is concluded that large earthquake is not a Poisson process but a phenomenon exhibiting a long-tail distribution. Based on the renewal theoretical analysis, we demonstrate that the sequence of earthquakes without correlated earthquakes are completely stationary.
Leemis, Larry
(x) = x-1 e-(1/)x x > 0. The Weibull distribution is used in reliability and survival analysis to modelWeibull distribution (from http://www.math.wm.edu/~leemis/chart/UDR/UDR.html) The shorthand X Weibull(, ) is used to indicate that the random variable X has the Weibull distribution with scale
Fuzzy Weibull for risk analysis
David P. Weber
1994-01-01
Reliability and the life of components are frequently prime safety considerations. Extensive qualitative analysis employing probabilistic risk assessment has been widely performed to minimize hazards or accidents. Weibull probability data and information is a vital tool of quantitative risk assessments, but so are qualitative methods such as fault tree analysis. Qualitative aspects of product risk are subjective and contain many
Mechanical Properties of Feed Pellets: Weibull Analysis
K. A. Aarseth; E. Prestløkken
2003-01-01
Physical properties of feed pellets were investigated in the context of fracture mechanics of brittle materials. Such materials exhibit high scatter in strength due to variation in flaw sizes in the material, known as Griffith cracks. Weibull analysis assumes a relation between the size distribution of Griffith cracks and the scatter in fracture strength. This relation is outlined, and used
Understanding Web Browsing Behaviors through Weibull Analysis of Dwell Time
Dumais, Susan
Understanding Web Browsing Behaviors through Weibull Analysis of Dwell Time Chao Liu Microsoft- ity analysis, and propose to model the dwell time using the Weibull distribution. Using of user browsing behaviors not previ- ously reported. For example, our analysis reveals that Web browsing
Bayesian Inference and Life Testing Plan for the Weibull Distribution in Presence of
Kundu, Debasis
Bayesian Inference and Life Testing Plan for the Weibull Distribution in Presence of Progressive of the progressively censored Weibull distribution. It is well known that for a Weibull distribution, while computing to observe the behavior of the proposed methods, and a data analysis is conducted for illustrative purposes
Weibull analysis of the mechanical strength of silica gels
L. Duffours; F. Pernot; T. Woignier; A. Alaoui; J. Phalippou
1994-01-01
Since gels are typically brittle materials, reliable analyses are essential to determine the strength distribution. The mechanical strength of silica gels has been measured by the three point bending technique. Based on the Weibull function, the statistical analysis allows determination of the Weibull modulus (m), which characterizes the strength distribution and the flaw size effect.
FAST ABSTRACT: Vulnerability Discovery Modeling using Weibull Distribution
Malaiya, Yashwant K.
. The AML Logistic model has been found to provide the best fit in several cases. Weibull distribution in Figure 1. Figure 1. Weibull and Logistic distributions Weibull distribution is often used for reliability evaluation for hardware systems. Both logistic and Weibull distributions will result in a cumulative
NASA Technical Reports Server (NTRS)
Kranz, Timothy L.
2002-01-01
The Weibull distribution has been widely adopted for the statistical description and inference of fatigue data. This document provides user instructions, examples, and verification for software to analyze gear fatigue test data. The software was developed presuming the data are adequately modeled using a two-parameter Weibull distribution. The calculations are based on likelihood methods, and the approach taken is valid for data that include type I censoring. The software was verified by reproducing results published by others.
NASA Technical Reports Server (NTRS)
Krantz, Timothy L.
2002-01-01
The Weibull distribution has been widely adopted for the statistical description and inference of fatigue data. This document provides user instructions, examples, and verification for software to analyze gear fatigue test data. The software was developed presuming the data are adequately modeled using a two-parameter Weibull distribution. The calculations are based on likelihood methods, and the approach taken is valid for data that include type 1 censoring. The software was verified by reproducing results published by others.
Weibull Distribution From Interval Inspection Data
NASA Technical Reports Server (NTRS)
Rheinfurth, Mario H.
1987-01-01
Most likely failure sequence assumed. Memorandum discusses application of Weibull distribution to statistics of failures of turbopump blades. Is generalization of well known exponential random probability distribution and useful in describing component-failure modes including aging effects. Parameters found from experimental data by method of maximum likelihood.
Sequential tests for Weibull distributed observations
Sequential tests for Weibull distributed observations Nadja R¨uckert, Karl-Heinz Eger Chemnitz.rueckert@mathematik.tu-chemnitz.de eger@mathematik.tu-chemnitz.de Abstract This paper deals with two kinds of sequential tests for grouped sequential ratio test for testing the form parameter and determine the appropriate OC- and ASN
Weibull statistical analysis of granite bending strength
P. M. Amaral; J. Cruz Fernandes; L. Guerra Rosa
2008-01-01
This paper describes and discusses the adequacy of Weibull statistical analysis to analyse the bending strength of granite. The experimental results show that strength variability is related with a specific origin of failure. This conclusion is based on analysing the influence of the surface condition (extrinsic defects) on the bending strength results treated by the Weibull statistics. The conclusions drawn
BAYESIAN ANALYSIS FOR MASKED SYSTEM FAILURE DATA USING NONIDENTICAL WEIBULL MODELS
Basu, Sanjib
BAYESIAN ANALYSIS FOR MASKED SYSTEM FAILURE DATA USING NONIDENTICAL WEIBULL MODELS by Sanjib Basu to a subsystem or a smaller set of components. A Bayesian analysis is developed in this article for such masked to have independent Weibull distributions. These K Weibulls can have different scale and shape parameters
JOURNAL OF MATERIALS SCIENCE 37 (2002) 1401 1406 Weibull analysis of the tensile behavior of fibers
Pan, Ning
2002-01-01
JOURNAL OF MATERIALS SCIENCE 37 (2002) 1401 1406 Weibull analysis of the tensile behavior the conventional Weibull/weakest-link model by incorporating the within-fiber diameter variation. This is necessary. The strength of wool fibers has been verified to follow this modified Weibull/weakest-link distribution
Bayesian Analysis of Simple Step-stress Model under Weibull Lifetimes
Kundu, Debasis
Bayesian Analysis of Simple Step-stress Model under Weibull Lifetimes A. Ganguly1 , D. Kundu2, 3-stress model under different censoring schemes based on Weibull lifetimes is considered in this paper also increases. We provide Bayesian inference of the unknown param- eters of the Weibull distribution
Estimation problems associated with the Weibull distribution
Bowman, K O; Shenton, L R
1981-09-01
Series in descending powers of the sample size are developed for the moments of the coefficient of variation v* for the Weibull distribution F(t) = 1 -exp(-(t/b)/sup c/). A similar series for the moments of the estimator c* of the shape parameter c are derived from these. Comparisons are made with basic asymptotic assessments for the means and variances. From the first four moments, approximations are given to the distribution of v* and c*. In addition, an almost unbiased estimator of c is given when a sample is provided with the value of v*. Comments are given on the validity of the asymptotically normal assessments of the distributions.
Weibull statistical analysis of granite bending strength
P. M. Amaral; J. Cruz Fernandes; L. Guerra Rosa
2008-01-01
Summary This paper describes and discusses the adequacy of Weibull statistical analysis to analyse the bending strength of granite.\\u000a The experimental results show that strength variability is related with a specific origin of failure. This conclusion is based\\u000a on analysing the influence of the surface condition (extrinsic defects) on the bending strength results treated by the Weibull\\u000a statistics. The conclusions drawn
Independent Orbiter Assessment (IOA): Weibull analysis report
NASA Technical Reports Server (NTRS)
Raffaelli, Gary G.
1987-01-01
The Auxiliary Power Unit (APU) and Hydraulic Power Unit (HPU) Space Shuttle Subsystems were reviewed as candidates for demonstrating the Weibull analysis methodology. Three hardware components were identified as analysis candidates: the turbine wheel, the gearbox, and the gas generator. Detailed review of subsystem level wearout and failure history revealed the lack of actual component failure data. In addition, component wearout data were not readily available or would require a separate data accumulation effort by the vendor. Without adequate component history data being available, the Weibull analysis methodology application to the APU and HPU subsystem group was terminated.
Is the Weibull distribution really suited for wind statistics modeling?
NASA Astrophysics Data System (ADS)
Drobinski, Philippe; Coulais, Corentin; Jourdier, Bénédicte
2014-05-01
Wind speed statistics is generally modeled using the Weibull distribution. This distribution is convenient since it fully characterizes analytically with only two parameters (the shape and scale parameters) the shape of distribution and the different moments of the wind speed. However, the Weibull distribution is based on empirical rather than physical justification and might display strong limitations for its applications. In this article, we analyze wind speed distributions of meteorological stations and report that they deviate from the Weibull distribution. We further investigate wind components rather than the wind speed statistic. This approach provides more physical insights on the validity domain of the Weibull distribution as a possible relevant model for wind statistics and the quantification of the error made by using such a distribution. We thereby propose alternative expressions of more suited wind speed distribution by using super-statistical distributions.
Program for Weibull Analysis of Fatigue Data
NASA Technical Reports Server (NTRS)
Krantz, Timothy L.
2005-01-01
A Fortran computer program has been written for performing statistical analyses of fatigue-test data that are assumed to be adequately represented by a two-parameter Weibull distribution. This program calculates the following: (1) Maximum-likelihood estimates of the Weibull distribution; (2) Data for contour plots of relative likelihood for two parameters; (3) Data for contour plots of joint confidence regions; (4) Data for the profile likelihood of the Weibull-distribution parameters; (5) Data for the profile likelihood of any percentile of the distribution; and (6) Likelihood-based confidence intervals for parameters and/or percentiles of the distribution. The program can account for tests that are suspended without failure (the statistical term for such suspension of tests is "censoring"). The analytical approach followed in this program for the software is valid for type-I censoring, which is the removal of unfailed units at pre-specified times. Confidence regions and intervals are calculated by use of the likelihood-ratio method.
Blind signal separation using an adaptive weibull distribution
M. El-Sayed Waheed
2009-01-01
We propose an independent component analysis (ICA) algorithm which can separate mixtures of sub- and super- Gaussian source signals with self-adaptive nonlinearities. The ICA algorithem in the framework of natural Riemannian gradient is derived using the parameterized Weibull density model. The nonlinear function in ICA algorithem is self-adaptive and is controlled by the shape parameter of Weibull density model. Computer
Performance analysis of predetection EGC receiver in Weibull fading channel
Chaturvedi, A K
Performance analysis of predetection EGC receiver in Weibull fading channel P.R. Sahu and A been analysed for an independent Weibull fading channel. Numerical results have been compared with the available results for selection combining (SC) and MRC diversity receivers. Introduction: The Weibull fading
Weibull model of Multiplicity Distribution in hadron-hadron collisions
Sadhana Dash; Basanta K. Nandi
2014-09-19
We introduce the Weibull distribution as a simple parametrization of charged particle multiplicities in hadron-hadron collisions at all available energies, ranging from ISR energies to the most recent LHC energies. In statistics, the Weibull distribution has wide applicability in natural processes involving fragmentation processes. This gives a natural connection to the available state-of-the-art models for multi-particle production in hadron hadron collisions involving QCD parton fragmentation and hadronization.
Weibull distribution based on maximum likelihood with interval inspection data
NASA Technical Reports Server (NTRS)
Rheinfurth, M. H.
1985-01-01
The two Weibull parameters based upon the method of maximum likelihood are determined. The test data used were failures observed at inspection intervals. The application was the reliability analysis of the SSME oxidizer turbine blades.
Bayesian estimation of life parameters in the Weibull distribution.
NASA Technical Reports Server (NTRS)
Canavos, G. C.; Tsokos, C. P.
1973-01-01
Development of a Bayesian analysis of the scale and shape parameters in the Weibull distribution and the corresponding reliability function with respect to the usual life-testing procedures. For the scale parameter theta, Bayesian estimates of theta and reliability are obtained for the uniform, exponential, and inverted gamma prior probability densities. Bhattacharya's results (1967) for the one-parameter exponential life-testing distribution are reduced to a special case of these results. A fully Bayesian analysis of both the scale and shape parameters is developed by assuming independent prior distributions; since in the latter case, analytical tractability is not possible, Bayesian estimates are obtained through a conjunction of Monte Carlo simulation and numerical-integration techniques. In both cases, a computer simulation is carried out, and a comparison is made between the Bayesian and the corresponding minimum-variance unbiased, or maximum likelihood, estimates. As expected, the Bayesian estimates are superior.
Modeling surfactant-induced hemolysis by Weibull survival analysis
Sagit Shalel; Sara Streichman; Abraham Marmur
2003-01-01
It is demonstrated that surfactant-induced, slow hemolysis (usually attributed to an osmotic mechanism) is very well described by the two-parameter Weibull distribution. The Weibull shape parameter depends on blood properties. The Weibull scale parameter is found to be determined by the amount of membrane-bound surfactant per cell, which is controlled by the suspending solution composition. For hemolysis that involves also
Weibull analysis of soldered MLC under bending load stress
Klaus Franken; Horst R. Maier
1999-01-01
A two-dimensional numerical model of MLCs is used to calculate the overall stress distribution of soldered and bent MLCs. Together with bending measurements the stress distribution leads to the Weibull parameters of three different MLC sizes. The material dependent Weibull parameters have been found to be different for each size. One possible reason under investigation are size related residual stresses
A cautionary tale about Weibull analysis [reliability estimation
M. S. Mackisack; R. H. Stillman
1996-01-01
This paper makes three points about possible perils of unguarded fitting of Weibull distributions to data: (1) bias is introduced by incomplete data, which may have counter-intuitive effects; (2) bias is introduced into percentile estimates by using regression on log-transformed variables to fit the Weibull parameters, particularly if the percentile to be predicted lies outside the range of the data;
Weibull analysis of ceramics under high stress gradients
T. Fett; E. Ernst; D. Munz; D. Badenheim; R. Oberacker
2003-01-01
The Weibull parameter m of the strength distribution of ceramics under high stress gradients differs from that for moderate stress gradients. This is shown for contact loading. Bars were loaded by oppositely concentrated forcers via rollers. For most investigated materials, measured contact strengths showed strongly reduced Weibull exponents compared with those from 4-point bending tests. This was the reason for
Evaluation of Methods to Predict Weibull Parameters for Characterizing Diameter Distributions
Cao, Quang V.
Evaluation of Methods to Predict Weibull Parameters for Characterizing Diameter Distributions and relative simplicity. Parameters of the Weibull distribution are generally predicted either by the parameter prediction method or by the parameter recovery method. The coefficients of the regression equations
Monte Carlo Evaluation and Development of Weibull Analysis Techniques
Lloyd Schlitzer
1966-01-01
Monte Carlo simulation studies have been conducted to provide improved techniques for fatigue data analysis with the Weibull equation. Three methods of estimating the Weibull parameters were evaluated by empirically measuring the bias associated with each method when used on data from small samples. Various methods of treating suspended data were similarly compared. Confidence bands were then developed on the
Fitting Weibull distribution to ultraviolet solar radiation data
NASA Astrophysics Data System (ADS)
Ghitany, M. E.; El-Nashar, N. F.
2005-12-01
The aim of this paper is to fit the Weibull probability distribution to recently published data on monthly average daily ultraviolet (UV) radiation over Kuwait. The goodness-of-fit of the Weibull model is demonstrated both graphically and via several statistical tests such as modified Anderson Darling, Cramer von Mises, and Kolmogorov Smirnov tests. As a result, we can estimate statistical measures associated with monthly average daily UV radiation data such as the mean, median, mode, and standard deviation of the monthly average daily UV radiation over Kuwait.
Investigation of Weibull statistics in fracture analysis of cast aluminum
NASA Technical Reports Server (NTRS)
Holland, F. A., Jr.; Zaretsky, E. V.
1989-01-01
The fracture strengths of two large batches of A357-T6 cast aluminum coupon specimens were compared by using two-parameter Weibull analysis. The minimum number of these specimens necessary to find the fracture strength of the material was determined. The applicability of three-parameter Weibull analysis was also investigated. A design methodolgy based on the combination of elementary stress analysis and Weibull statistical analysis is advanced and applied to the design of a spherical pressure vessel shell. The results from this design methodology are compared with results from the applicable ASME pressure vessel code.
Investigation of Weibull statistics in fracture analysis of cast aluminum
NASA Technical Reports Server (NTRS)
Holland, Frederic A., Jr.; Zaretsky, Erwin V.
1989-01-01
The fracture strengths of two large batches of A357-T6 cast aluminum coupon specimens were compared by using two-parameter Weibull analysis. The minimum number of these specimens necessary to find the fracture strength of the material was determined. The applicability of three-parameter Weibull analysis was also investigated. A design methodology based on the combination of elementary stress analysis and Weibull statistical analysis is advanced and applied to the design of a spherical pressure vessel shell. The results from this design methodology are compared with results from the applicable ASME pressure vessel code.
NASA Technical Reports Server (NTRS)
Giuntini, Michael E.; Giuntini, Ronald E.
1991-01-01
A Bayesian inference process for system logistical planning is presented which provides a method for incorporating actual failures with prediction data for an ongoing and improving reliability estimates. The process uses the Weibull distribution, and provides a means for examining and updating logistical and maintenance support needs.
Fracture toughness of pea: Weibull analysis
Grzegorz ?ysiak
2007-01-01
The study focuses on evaluation of the fracture behavior of peas by examining the effect of moisture content upon seed fracture toughness and Weibull modulus. Individual pea seeds with varying water content between 4% and 20% (wet basis) were compressed using a universal testing machine, Zwick Z020. On the basis of recorded load–deformation curves, three different toughness indices were determined.
Table for estimating parameters of Weibull distribution
NASA Technical Reports Server (NTRS)
Mann, N. R.
1971-01-01
Table yields best linear invariant /BLI/ estimates for log of reliable life under censored life tests, permitting reliability estimations in failure analysis of items with multiple flaws. These BLI estimates have uniformly smaller expected loss than Gauss-Markov best linear unbiased estimates.
Weibull analysis techniques on a desktop computer
J. L. Byers
1988-01-01
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
Estimation of the parameters of the Weibull distribution from multi-censored samples
Sprinkle, Edgar Eugene
1969-01-01
when a & 1. For the Weibull distribution given by equations (2. 1) and (2. 2), a is a shape parameter and 8 is a scale parameter. Although the Weibull distribution seems to closely fit many reliability situations, when the parameters.... , 1956. "A new life-quality measure foz electron tubes, " IRE Transactions on unlit Control, 7, 1-11. KAO, J. H. K. , 1958. "Computer methods for estimating Weibull parameters in reliability studies, " IRE Transactions on Reliabil- it and alit Control...
Transformer insulation reliability for moving oil with weibull analysis
Toshihiro Tsuboi; Jun Takami; Shigemitsu Okabe; Kiyoshi Inami; Kazuaki Aono
2010-01-01
To develop test conditions for a short-duration power-frequency withstand voltage test, which is one of the insulation specifications of substation equipment, the reliability can be precisely evaluated using a Weibull distribution function. This can be done by either the independence model or accumulation model, which have been proposed in order to handle the coexistence of multiple voltage levels, although the
Weibull statistical analysis of area and volume effects on the breakdown strength in liquid nitrogen
H. Goshima; N. Hayakawa; M. Hikita; H. Okubo; K. Uchida
1995-01-01
In order to examine the area and the volume effects on breakdown strength in liquid nitrogen (LN2), we measured dc and ac breakdown voltages in LN2 with sphere to plane and coaxial cylindrical electrode configurations. We also carried out statistical analysis of the experimental results using the Weibull distribution and discussed with the statistical stressed electrode area (SSEA) and\\/or liquid
Lower bound on reliability for Weibull distribution when shape parameter is not estimated accurately
NASA Technical Reports Server (NTRS)
Huang, Zhaofeng; Porter, Albert A.
1991-01-01
The mathematical relationships between the shape parameter Beta and estimates of reliability and a life limit lower bound for the two parameter Weibull distribution are investigated. It is shown that under rather general conditions, both the reliability lower bound and the allowable life limit lower bound (often called a tolerance limit) have unique global minimums over a range of Beta. Hence lower bound solutions can be obtained without assuming or estimating Beta. The existence and uniqueness of these lower bounds are proven. Some real data examples are given to show how these lower bounds can be easily established and to demonstrate their practicality. The method developed here has proven to be extremely useful when using the Weibull distribution in analysis of no-failure or few-failures data. The results are applicable not only in the aerospace industry but anywhere that system reliabilities are high.
Lower bound on reliability for Weibull distribution when shape parameter is not estimated accurately
NASA Technical Reports Server (NTRS)
Huang, Zhaofeng; Porter, Albert A.
1990-01-01
The mathematical relationships between the shape parameter Beta and estimates of reliability and a life limit lower bound for the two parameter Weibull distribution are investigated. It is shown that under rather general conditions, both the reliability lower bound and the allowable life limit lower bound (often called a tolerance limit) have unique global minimums over a range of Beta. Hence lower bound solutions can be obtained without assuming or estimating Beta. The existence and uniqueness of these lower bounds are proven. Some real data examples are given to show how these lower bounds can be easily established and to demonstrate their practicality. The method developed here has proven to be extremely useful when using the Weibull distribution in analysis of no-failure or few-failures data. The results are applicable not only in the aerospace industry but anywhere that system reliabilities are high.
NASA Astrophysics Data System (ADS)
Goh, Segun; Kwon, H. W.; Choi, M. Y.
2014-06-01
We consider the Yule-type multiplicative growth and division process, and describe the ubiquitous emergence of Weibull and log-normal distributions in a single framework. With the help of the integral transform and series expansion, we show that both distributions serve as asymptotic solutions of the time evolution equation for the branching process. In particular, the maximum likelihood method is employed to discriminate between the emergence of the Weibull distribution and that of the log-normal distribution. Further, the detailed conditions for the distinguished emergence of the Weibull distribution are probed. It is observed that the emergence depends on the manner of the division process for the two different types of distribution. Numerical simulations are also carried out, confirming the results obtained analytically.
Weibull analysis applied to the pull adhesion test and fracture of a metal-ceramic interface
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
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.
A spatial scan statistic for survival data based on Weibull distribution.
Bhatt, Vijaya; Tiwari, Neeraj
2014-05-20
The spatial scan statistic has been developed as a geographical cluster detection analysis tool for different types of data sets such as Bernoulli, Poisson, ordinal, normal and exponential. We propose a scan statistic for survival data based on Weibull distribution. It may also be used for other survival distributions, such as exponential, gamma, and log normal. The proposed method is applied on the survival data of tuberculosis patients for the years 2004-2005 in Nainital district of Uttarakhand, India. Simulation studies reveal that the proposed method performs well for different survival distribution functions. PMID:24353112
Large-Scale Weibull Analysis of H-451 Nuclear- Grade Graphite Specimen Rupture Data
NASA Technical Reports Server (NTRS)
Nemeth, Noel N.; Walker, Andrew; Baker, Eric H.; Murthy, Pappu L.; Bratton, Robert L.
2012-01-01
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 excised from a single extruded graphite log. Strength variation was compared with specimen location, size, and orientation relative to the parent body. In our study, data were progressively and extensively pooled into larger data sets to discriminate overall trends from local variations and to investigate the strength distribution. The CARES/Life and WeibPar codes were used to investigate issues regarding the size effect, Weibull parameter consistency, and nonlinear stress-strain response. Overall, the Weibull distribution described the behavior of the pooled data very well. However, the issue regarding the smaller-than-expected size effect remained. This exercise illustrated that a conservative approach using a two-parameter Weibull distribution is best for designing graphite components with low probability of failure for the in-core structures in the proposed Generation IV (Gen IV) high-temperature gas-cooled nuclear reactors. This exercise also demonstrated the continuing need to better understand the mechanisms driving stochastic strength response. Extensive appendixes are provided with this report to show all aspects of the rupture data and analytical results.
Parameter estimation for a modified Weibull distribution, for progressively type-II censored samples
H. K. T. Ng
2005-01-01
In this paper, the estimation of parameters based on a progressively Type-II censored sample from a modified Weibull distribution is studied. The likelihood equations, and the maximum likelihood estimators are derived. The estimators based on a least-squares fit of a multiple linear regression on a Weibull probability paper plot are compared with the MLE via Monte Carlo simulations. The observed
Weibull statistical analysis of impulse-driven surface breakdown data
M. P. Wilson; M. J. Given; I. V. Timoshkin; S. J. MacGregor; T. Wang; M. A. Sinclair; K. J. Thomas; J. M. Lehr
2011-01-01
Surface breakdown of oil-immersed solids chosen to insulate high-voltage, pulsed-power systems is a problem that can lead to catastrophic failure. Statistical analysis of the breakdown voltages associated with such liquid-solid interfaces can reveal useful information to aid system designers in the selection of solid materials. Described in this paper are the results of a Weibull statistical analysis, applied to breakdown
A comparison of the generalized gamma and exponentiated Weibull distributions.
Cox, Christopher; Matheson, Matthew
2014-09-20
This paper provides a comparison of the three-parameter exponentiated Weibull (EW) and generalized gamma (GG) distributions. The connection between these two different families is that the hazard functions of both have the four standard shapes (increasing, decreasing, bathtub, and arc shaped), and in fact, the shape of the hazard is the same for identical values of the three parameters. For a given EW distribution, we define a matching GG using simulation and also by matching the 5 (th) , 50 (th) , and 95 (th) percentiles. We compare EW and matching GG distributions graphically and using the Kullback-Leibler distance. We find that the survival functions for the EW and matching GG are graphically indistinguishable, and only the hazard functions can sometimes be seen to be slightly different. The Kullback-Leibler distances are very small and decrease with increasing sample size. We conclude that the similarity between the two distributions is striking, and therefore, the EW represents a convenient alternative to the GG with the identical richness of hazard behavior. More importantly, these results suggest that having the four basic hazard shapes may to some extent be an important structural characteristic of any family of distributions. PMID:24700647
Estimation of the parameters of the Weibull distribution from multi-censored samples
Sprinkle, Edgar Eugene
1969-01-01
ESTIMATION OF THE PARAMETERS OF THE WEIBULL DISTRIBUTION FROM MULTI-CENSORED SAMPLES A Thesis by EDGAR EUGENE SPRINKLE, III Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement for the degree... of MASTER OF SCIENCE May 1969 Major Subject: Statistics ESTIMATION OF THE PARAMETERS OF THE WEIBULL DISTRIBUTION FROM MULTI-CENSORED SAMPLES A Thesis EDGAR EUGENE SPRINKLE, III Approved as to style and content by: (Head of Department) (Member...
David M. Nanang
1998-01-01
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
NASA Technical Reports Server (NTRS)
Gross, Bernard
1996-01-01
Material characterization parameters obtained from naturally flawed specimens are necessary for reliability evaluation of non-deterministic advanced ceramic structural components. The least squares best fit method is applied to the three parameter uniaxial Weibull model to obtain the material parameters from experimental tests on volume or surface flawed specimens subjected to pure tension, pure bending, four point or three point loading. Several illustrative example problems are provided.
Weibull analysis of the tensile behavior of fibers with geometrical irregularities
Yuping Zhang; Xungai Wang; Ning Pan; R. Postle
2002-01-01
This paper further develops the conventional Weibull\\/weakest-link model by incorporating the within-fiber diameter variation. This is necessary for fibers with considerable geometrical irregularities, such as the wool and other animal fibers. The strength of wool fibers has been verified to follow this modified Weibull\\/weakest-link distribution. In addition, the modified Weibull model can predict the gauge length effect more accurately than
A failure-forecast method based on Weibull and statistical-pattern analysis
Kevin Fitzgibbon; Ron Barker; T. Clayton; N. Wilson
2002-01-01
This paper presents a method that combines Weibull analysis and statistical algorithms to forecast failures, and the experimental results applied to electronic systems. The Weibull analysis is a classical method to forecast failures using risk analysis and the mean-time-to-failure (MTTF) parameter. Statistical pattern analysis can forecast failures based on performance information from the component. Performance can be monitored by analyzing
Is the Weibull distribution really suited for wind statistics modeling and wind power evaluation?
Drobinski, Philippe
2012-01-01
Wind speed statistics is generally modeled using the Weibull distribution. This distribution is convenient since it fully characterizes analytically with only two parameters (the shape and scale parameters) the shape of distribution and the different moments of the wind speed (mean, standard deviation, skewness and kurtosis). This distribution is broadly used in the wind energy sector to produce maps of wind energy potential. However, the Weibull distribution is based on empirical rather than physical justification and might display strong limitations for its applications. The philosophy of this article is based on the modeling of the wind components instead of the wind speed itself. This provides more physical insights on the validity domain of the Weibull distribution as a possible relevant model for wind statistics and the quantification of the error made by using such a distribution. We thereby propose alternative expressions of more suited wind speed distribution.
Weibull statistical analysis of quench current of a.c. superconducting wires and coils
Naoki Hayakawa; Mikio Wakita; Masayuki Hikita; Hitoshi Okubo
1997-01-01
Quench of superconducting wires can be regarded as probabilistic phenomena due to local instability in the wire. This paper describes statistical scattering in quench current of a.c. superconducting wires and coils using Weibull statistics. Experimental results revealed that, in some cases, the scattering was expressed by mixed Weibull distribution with different shape parameters. These results suggested that there could exist
NASA Astrophysics Data System (ADS)
Bertalan, Zsolt; Shekhawat, Ashivni; Sethna, James P.; Zapperi, Stefano
2014-09-01
The statistical properties of fracture strength of brittle and quasibrittle materials are often described in terms of the Weibull distribution. However, the weakest-link hypothesis, commonly used to justify it, is expected to fail when fracture occurs after significant damage accumulation. Here we show that this implies that the Weibull distribution is unstable in a renormalization-group sense for a large class of quasibrittle materials. Our theoretical arguments are supported by numerical simulations of disordered fuse networks. We also find that for brittle materials such as ceramics, the common assumption that the strength distribution can be derived from the distribution of preexisting microcracks by using Griffith's criteria is invalid. We attribute this discrepancy to crack bridging. Our findings raise questions about the applicability of Weibull statistics to most practical cases.
Characterizing size dependence of ceramic-fiber strength using modified Weibull distribution
Zhu, Yuntian; Blumenthal, W.R.
1995-05-01
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.
Fuzzy Reliability Design of Robot Parts Based on Weibull and Normal Distribution
Tie Wang; Gaonan Wang; Yizhou Liu; Shuwen Zhou
2008-01-01
With considering lightening and safety of strength, integrations of both distributionpsilas density and functionpsilas density, the normal fuzzy reliability formulas about robot parts that forces are normal distribution, strengths are Weibull distribution and subordinate is gamma function was gotten; first integral change was achieved according to initial data and function imported and extent of integrated, second the number result with
Le, Cui; Wanxi, Peng; Zhengjun, Sun; Lili, Shang; Guoning, Chen
2014-07-01
Bamboo is a radial gradient variation composite material against parasitology and vector biology, but the vascular bundles in inner layer are evenly distributed. The objective is to determine the regular size pattern and Weibull statistical analysis of the vascular bundle tensile strength in inner layer of Moso bamboo. The size and shape of vascular bundles in inner layer are similar, with an average area about 0.1550 mm2. A statistical evaluation of the tensile strength of vascular bundle was conducted by means of Weibull statistics, the results show that the Weibull modulus m is 6.1121 and the accurate reliability assessment of vascular bundle is determined. PMID:25016270
J. Huang; C. R. Miller; O. G. Okogbaa
1995-01-01
Using a well-known single-unit replacement model with Weibull failure distribution assumption, normalization is used to reduce the model input parameters such that standard optimal preventive replacement solutions can be generated. Characteristics of the model solutions are discussed. The standard solutions are organized in charts and tables for ease of use. Procedures are developed and examples are given for applying the
P. Mafart; O. Couvert; S. Gaillard; I. Leguerinel
2002-01-01
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
Shigeta Moril; Akio Hagihara
1991-01-01
Thirten sample trees of various sizes in a 29-year-old hinoki [Chamaecyparis obtusa (Sieb, et Zucc.) Endl.] plantation were felled and subjected to the stratified clip technique. Crown profile of foliage area fitted well with the Weibull distribution. The crown profile tended to be more skewed toward the top of crowns in smaller trees than in larger trees. This tendency was
An EOQ Model with Two-Parameter Weibull Distribution Deterioration and Price-Dependent Demand
ERIC Educational Resources Information Center
Mukhopadhyay, Sushanta; Mukherjee, R. N.; Chaudhuri, K. S.
2005-01-01
An inventory replenishment policy is developed for a deteriorating item and price-dependent demand. The rate of deterioration is taken to be time-proportional and the time to deterioration is assumed to follow a two-parameter Weibull distribution. A power law form of the price dependence of demand is considered. The model is solved analytically…
Weibull-distributed dyke thickness reflects probabilistic character of host-rock strength
NASA Astrophysics Data System (ADS)
Krumbholz, Michael; Hieronymus, Christoph F.; Burchardt, Steffi; Troll, Valentin R.; Tanner, David C.; Friese, Nadine
2014-02-01
Magmatic sheet intrusions (dykes) constitute the main form of magma transport in the Earth’s crust. The size distribution of dykes is a crucial parameter that controls volcanic surface deformation and eruption rates and is required to realistically model volcano deformation for eruption forecasting. Here we present statistical analyses of 3,676 dyke thickness measurements from different tectonic settings and show that dyke thickness consistently follows the Weibull distribution. Known from materials science, power law-distributed flaws in brittle materials lead to Weibull-distributed failure stress. We therefore propose a dynamic model in which dyke thickness is determined by variable magma pressure that exploits differently sized host-rock weaknesses. The observed dyke thickness distributions are thus site-specific because rock strength, rather than magma viscosity and composition, exerts the dominant control on dyke emplacement. Fundamentally, the strength of geomaterials is scale-dependent and should be approximated by a probability distribution.
Weibull-distributed dyke thickness reflects probabilistic character of host-rock strength.
Krumbholz, Michael; Hieronymus, Christoph F; Burchardt, Steffi; Troll, Valentin R; Tanner, David C; Friese, Nadine
2014-01-01
Magmatic sheet intrusions (dykes) constitute the main form of magma transport in the Earth's crust. The size distribution of dykes is a crucial parameter that controls volcanic surface deformation and eruption rates and is required to realistically model volcano deformation for eruption forecasting. Here we present statistical analyses of 3,676 dyke thickness measurements from different tectonic settings and show that dyke thickness consistently follows the Weibull distribution. Known from materials science, power law-distributed flaws in brittle materials lead to Weibull-distributed failure stress. We therefore propose a dynamic model in which dyke thickness is determined by variable magma pressure that exploits differently sized host-rock weaknesses. The observed dyke thickness distributions are thus site-specific because rock strength, rather than magma viscosity and composition, exerts the dominant control on dyke emplacement. Fundamentally, the strength of geomaterials is scale-dependent and should be approximated by a probability distribution. PMID:24513695
NASA Astrophysics Data System (ADS)
Drobinski, Philippe; Coulais, Corentin; Jourdier, Bénédicte
2015-05-01
Wind-speed statistics are generally modelled using the Weibull distribution. However, the Weibull distribution is based on empirical rather than physical justification and might display strong limitations for its applications. Here, we derive wind-speed distributions analytically with different assumptions on the wind components to model wind anisotropy, wind extremes and multiple wind regimes. We quantitatively confront these distributions with an extensive set of meteorological data (89 stations covering various sub-climatic regions in France) to identify distributions that perform best and the reasons for this, and we analyze the sensitivity of the proposed distributions to the diurnal to seasonal variability. We find that local topography, unsteady wind fluctuations as well as persistent wind regimes are determinants for the performances of these distributions, as they induce anisotropy or non-Gaussian fluctuations of the wind components. A Rayleigh-Rice distribution is proposed to model the combination of weak isotropic wind and persistent wind regimes. It outperforms all other tested distributions (Weibull, elliptical and non-Gaussian) and is the only proposed distribution able to catch accurately the diurnal and seasonal variability.
Flexural strength of infrared-transmitting window materials: bimodal Weibull statistical analysis
Claude A. Klein
2011-01-01
The results of flexural strength testing performed on brittle materials are usually interpreted in light of a ``Weibull plot,'' i.e., by fitting the estimated cumulative failure probability (CFP) to a linearized semiempirical Weibull distribution. This procedure ignores the impact of the testing method on the measured stresses at fracture--specifically, the stressed area and the stress profile--thus resulting in inadequate characterization
Erck, R. A.; Nichols, F. A.; Lauer, B. A.; Energy Technology; Eastern Illinois Univ.
1994-01-01
Silver films were deposited by evaporation onto polished silicon carbide substrates that had been sputtered for various lengths of time with 500 eV ions. The adhesion strength of the films was measured as a function of the ion bombardment time and species with a pull-type adhesion tester. Adhesion of Ag to argon-ion-sputtered surfaces was low except at the highest dose, in which case very good adhesion was measured. In contrast, oxygen/argon-ion sputtering produced a rapid rise in adhesion strength, but adhesion was limited to less than 60 MPa, even for lengthy bombardment. The applicability of Weibull statistical analysis to the distribution of pull-test failure strengths was investigated. A good fit of the data to the Weibull expression was observed. A significant Weibull threshold stress was found and the Weibull modulus was low.
Robust 2 factorial design with Weibull error distributions
Birdal ?eno?lu
2005-01-01
It is well known that the least squares method is optimal only if the error distributions are normally distributed. However, in practice, non-normal distributions are more prevalent. If the error terms have a non-normal distribution, then the efficiency of least squares estimates and tests is very low. In this paper, we consider the 2 factorial design when the distribution of
Single versus mixture Weibull distributions for nonparametric satellite reliability
Jean-Francois Castet; Joseph H. Saleh
2010-01-01
Long recognized as a critical design attribute for space systems, satellite reliability has not yet received the proper attention as limited on-orbit failure data and statistical analyses can be found in the technical literature. To fill this gap, we recently conducted a nonparametric analysis of satellite reliability for 1584 Earth-orbiting satellites launched between January 1990 and October 2008. In this
B. Jankovic
2007-01-01
The powder sample of nickel oxide was synthesized by sol–gel procedure. The isothermal reduction of nickel oxide using hydrogen was investigated by thermogravimetric analysis at five operating temperatures: 245, 255, 265, 275 and 300°C. The kinetic triplet (Ea, A and f(?)) was determined using conventional and Weibull kinetic analysis. Both the kinetically procedures show that the reduction process considered can
Weibull statistical analysis of the mechanical strength of a glass eroded by sand blasting
M. A. Madjoubi; C. Bousbaa; M. Hamidouche; N. Bouaouadja
1999-01-01
In Saharian regions, the erosion of glass by sand particles during sandstorms is a regular phenomenon. The progressive loss of matter on surface affects both the optical transmission and mechanical strength. In this work, the influence of sand impacts on glass strength was simulated in laboratory. We used Weibull distribution function to characterize statistically the variation of the mechanical strength
R. V. Curtis; A. S. Juszczyk
2001-01-01
Objective: Phosphate-bonded investments are being investigated for use as die materials for dental superplastic forming. The effects of handling technique on the strengths of these investments needs to be determined. The purpose was to use methods of Weibull analysis to fit measured 4 point bend strength data and determine strength and Weibull modulus, where modulus represents the scatter of the
Discriminating Among the Log-Normal, Weibull and Generalized Exponential
Kundu, Debasis
Discriminating Among the Log-Normal, Weibull and Generalized Exponential Distributions Arabin Kumar to analyze lifetime data in the reliability analysis. We study the probability of correct selection using. 91-512- 2597500, e-mail: kundu@iitk.ac.in. 1 #12;1 Introduction Log-normal, Weibull and generalized
Flexural strength of infrared-transmitting window materials: bimodal Weibull statistical analysis
NASA Astrophysics Data System (ADS)
Klein, Claude A.
2011-02-01
The results of flexural strength testing performed on brittle materials are usually interpreted in light of a ``Weibull plot,'' i.e., by fitting the estimated cumulative failure probability (CFP) to a linearized semiempirical Weibull distribution. This procedure ignores the impact of the testing method on the measured stresses at fracture--specifically, the stressed area and the stress profile--thus resulting in inadequate characterization of the material under investigation. In a previous publication, the author reformulated Weibull's statistical theory of fracture in a manner that emphasizes how the stressed area and the stress profile control the failure probability distribution, which led to the concept of a characteristic strength, that is, the effective strength of a 1-cm2 uniformly stressed area. Fitting the CFP of IR-transmitting materials (AlON, fusion-cast CaF2, oxyfluoride glass, fused SiO2, CVD-ZnSe, and CVD-ZnS) was performed by means of nonlinear regressions but produced evidence of slight, systematic deviations. The purpose of this contribution is to demonstrate that upon extending the previously elaborated model to distributions involving two distinct types of defects--bimodal distributions--the fit agrees with estimated CFPs. Furthermore, the availability of two sets of statistical parameters (characteristic strength and shape parameter) can be taken advantage of to evaluate the failure-probability density, thus providing means of assessing the nature, the critical size, and the size distribution of surface/subsurface flaws.
Estimating Weibull parameters for materials
NASA Technical Reports Server (NTRS)
Robinson, E. Y.
1971-01-01
The statistical analysis of strength and fracture of materials in general, with application to fiber composites are discussed. The weakest link model is considered in a fairly general form, and the resulting equations are demonstrated by using a Weibull distribution for flaws. This distribution appears naturally in a variety of problems, and therefore additional attention is devoted to analysis and statistical estimation connected with this distribution. Special working charts are included to facilitate interpretation of observed data and estimation of parameters. Implications of the size effect are considered for various kinds of flaw distributions. Failure and damage in a fiber-reinforced system are described. Some useful graphs are included for predicting the strength of such a system. Recent data on organic-fiber (PRD 49) composite material is analyzed by the Weibull distribution with the methods presented.
Time Series Analysis of Particle Tracking Data for Molecular Motion on the Cell Membrane
Ying, Wenxia; Huerta, Gabriel; Steinberg, Stanly; Zúñiga, Martha
2009-01-01
Analysis of Particle Tracking Data for Molecular Motion The chi, Weibull, andgeneralized Weibull distribution. This analysis implies thatWeibull, and for ? the plots look linear. However, careful statistical analysis
Probabilistic Analysis for Comparing Fatigue Data Based on Johnson-Weibull Parameters
NASA Technical Reports Server (NTRS)
Hendricks, Robert C.; Zaretsky, Erwin V.; Vicek, Brian L.
2007-01-01
Probabilistic failure analysis is essential when analysis of stress-life (S-N) curves is inconclusive in determining the relative ranking of two or more materials. In 1964, L. Johnson published a methodology for establishing the confidence that two populations of data are different. Simplified algebraic equations for confidence numbers were derived based on the original work of L. Johnson. Using the ratios of mean life, the resultant values of confidence numbers deviated less than one percent from those of Johnson. It is possible to rank the fatigue lives of different materials with a reasonable degree of statistical certainty based on combined confidence numbers. These equations were applied to rotating beam fatigue tests that were conducted on three aluminum alloys at three stress levels each. These alloys were AL 2024, AL 6061, and AL 7075. The results were analyzed and compared using ASTM Standard E739-91 and the Johnson-Weibull analysis. The ASTM method did not statistically distinguish between AL 6010 and AL 7075. Based on the Johnson-Weibull analysis confidence numbers greater than 99 percent, AL 2024 was found to have the longest fatigue life, followed by AL 7075, and then AL 6061. The ASTM Standard and the Johnson-Weibull analysis result in the same stress-life exponent p for each of the three aluminum alloys at the median or L(sub 50) lives.
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...
Weibull mixture model for isoconversional kinetic analysis of biomass oxidative pyrolysis
NASA Astrophysics Data System (ADS)
Cai, J. M.; Chen, S. Y.
2010-03-01
In this work, the possibility of applying the weighted sum of three cumulative Weibull distribution functions for the fitting of the kinetic conversion data of biomass oxidative pyrolysis has been investigated. The kinetic conversion data of the thermal decomposition of olive oil solid waste in oxygen atmosphere for different heating rates have been analyzed. The results have shown that the experimental data can be perfectly reproduced by the general fitting function. Therefore, it is possible to obtain the corresponding conversion rate values of biomass oxidative pyrolysis by differentiating directly the fitted kinetic conversion data. Additionally, the logistic mixture model has been applied to the same experimental data. It can be found that the newly proposed function can provide a better fit of the data than the logistic mixture model. Based on the fitting of Weibull mixture model, the kinetic triples (E, A and f(?)) of oxidative pyrolysis of olive solid waste were obtained by means of Friedman's differential isoconversional method.
Probabilistic Analysis for Comparing Fatigue Data Based on Johnson-Weibull Parameters
NASA Technical Reports Server (NTRS)
Vlcek, Brian L.; Hendricks, Robert C.; Zaretsky, Erwin V.
2013-01-01
Leonard Johnson published a methodology for establishing the confidence that two populations of data are different. Johnson's methodology is dependent on limited combinations of test parameters (Weibull slope, mean life ratio, and degrees of freedom) and a set of complex mathematical equations. In this report, a simplified algebraic equation for confidence numbers is derived based on the original work of Johnson. The confidence numbers calculated with this equation are compared to those obtained graphically by Johnson. Using the ratios of mean life, the resultant values of confidence numbers at the 99 percent level deviate less than 1 percent from those of Johnson. At a 90 percent confidence level, the calculated values differ between +2 and 4 percent. The simplified equation is used to rank the experimental lives of three aluminum alloys (AL 2024, AL 6061, and AL 7075), each tested at three stress levels in rotating beam fatigue, analyzed using the Johnson- Weibull method, and compared to the ASTM Standard (E739 91) method of comparison. The ASTM Standard did not statistically distinguish between AL 6061 and AL 7075. However, it is possible to rank the fatigue lives of different materials with a reasonable degree of statistical certainty based on combined confidence numbers using the Johnson- Weibull analysis. AL 2024 was found to have the longest fatigue life, followed by AL 7075, and then AL 6061. The ASTM Standard and the Johnson-Weibull analysis result in the same stress-life exponent p for each of the three aluminum alloys at the median, or L(sub 50), lives
Understanding web browsing behaviors through Weibull analysis of dwell time
Chao Liu; Ryen W. White; Susan T. Dumais
2010-01-01
Dwell time on Web pages has been extensively used for vari- ous information retrieval tasks. However, some basic yet im- portant questions have not been sufficiently addressed, e.g., what distribution is appropriate to model the distribution of dwell times on a Web page, and furthermore, what the dis- tribution tells us about the underlying browsing behaviors. In this paper, we
Performance analysis with truncated heavy{tailed distributions
Asmussen, Søren
Performance analysis with truncated heavy{tailed distributions S#28;ren Asmussen #3;y Mats Pihlsg is heavy{tailed, say Pareto or Weibull, and a typically large K, say much larger than EU . We study, say Pareto or Weibull, and a typically large K, say much larger than EU . An earlier study
Fracture size effect in ultrananocrystalline diamond: Applicability of Weibull theory
Espinosa, Horacio D.
fractographic and transmission electron microscopy microstructural analysis. The Weibull parameters were in the strength of the polysilicon specimens. Weibull analysis predicted a general tendency for strengthFracture size effect in ultrananocrystalline diamond: Applicability of Weibull theory B. Peng, C
Performance Analysis of Wireless Single Input Multiple Output Systems (SIMO) in
Kouroupetroglou, Georgios
Performance Analysis of Wireless Single Input Multiple Output Systems (SIMO) in Correlated Weibull the statistical characteristics of the trivariate and quadrivariate Weibull fading distribution with arbitrary expressions for important joint statistics are derived using the Weibull power transformation
P. L Hall; J. E Strutt
2003-01-01
In reliability engineering, component failures are generally classified in one of three ways: (1) early life failures; (2) failures having random onset times; and (3) late life or ‘wear out’ failures. When the time-distribution of failures of a population of components is analysed in terms of a Weibull distribution, these failure types may be associated with shape parameters ? having
Bayesian Weibull tree models for survival analysis of clinico-genomic data
Clarke, Jennifer; West, Mike
2008-01-01
An important goal of research involving gene expression data for outcome prediction is to establish the ability of genomic data to define clinically relevant risk factors. Recent studies have demonstrated that microarray data can successfully cluster patients into low- and high-risk categories. However, the need exists for models which examine how genomic predictors interact with existing clinical factors and provide personalized outcome predictions. We have developed clinico-genomic tree models for survival outcomes which use recursive partitioning to subdivide the current data set into homogeneous subgroups of patients, each with a specific Weibull survival distribution. These trees can provide personalized predictive distributions of the probability of survival for individuals of interest. Our strategy is to fit multiple models; within each model we adopt a prior on the Weibull scale parameter and update this prior via Empirical Bayes whenever the sample is split at a given node. The decision to split is based on a Bayes factor criterion. The resulting trees are weighted according to their relative likelihood values and predictions are made by averaging over models. In a pilot study of survival in advanced stage ovarian cancer we demonstrate that clinical and genomic data are complementary sources of information relevant to survival, and we use the exploratory nature of the trees to identify potential genomic biomarkers worthy of further study. PMID:18618012
K. A. Aarseth; M. Sørensen; T. Storebakken
2006-01-01
Enhancement of fish feed extrusion-technology and improvements of technical pellet quality requires knowledge about causal connections amongst variables of processing condition and raw materials, and how these connections can be elucidated by measurements. Weibull analysis of feed pellet tensile strengths may represent one possible measurement tool for this purpose; this analysis is evaluated here and compared with the Holmen durability
Paris-Sud XI, Université de
1 2 On calculating sterility in thermal preservation methods :3 application of the Weibull method was then proposed to assess this decade14 reduction or to optimize the heat treatment for a target of calculating the efficiency of heat treatments in food protection is18 based on the assumption that survival
Bayesian and Maximum Likelihood Estimations of the Inverse Weibull Parameters Under Progressive
Kundu, Debasis
Bayesian and Maximum Likelihood Estimations of the Inverse Weibull Parameters Under ProgressiveDepartment of Quantitative Analysis, College of Business Administration, King Saud University, P.O. Box 2459 inverse Weibull (IW) distribution based on the progressive Type-II censored sample has been considered
Roy, Aparna; Chakraborty, Sumit; Kundu, Sarada Prasad; Basak, Ratan Kumar; Majumder, Subhasish Basu; Adhikari, Basudam
2012-03-01
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
RELATIONSHIP BETWEEN THE COX, LEHMANN, WEIBULL,
Loya, Paul
Cox and Oakes (1984) claim: a model satisfies AL and PH iff it is Weibull. (see "Analysis of survivalRELATIONSHIP BETWEEN THE COX, LEHMANN, WEIBULL, ACCELERATED LIFETIME MODELS By Qiqing Yu Department variable (vector); , , , are parameters Important parametric model: Weibull model S(t|x) = exp
Bimodal Weibull statistical analysis of CVD-ZnSe and CVD-ZnS flexural strength data
NASA Astrophysics Data System (ADS)
Klein, Claude A.
2011-06-01
The results of flexural strength The results of flexural strength testing performed on brittle materials are usually interpreted in the light of a "Weibull plot," i.e., by fitting the estimated cumulative failure probability (CFP) to a linearized semiempirical Weibull distribution. This procedure ignores the impact of the testing method on the measures stressed at failure-specifically the stressed area and the stress profile-thus resulting in an inadequate characterization of the material under consideration. In a previous publication [Opt. Eng. 41, 3151 (2002)] the author reformulated Weibull's statistical theory of fracture in a manner that emphasizes how the stressed area and the stress profile control the CFP, a 1-sq.cm uniformly stressed area. Fitting the CFP of IR-transmitting materials was performed by means of nonlinear regressions but produced evidence of systematic deviations. In this paper we demonstrate that, upon extending the previously elaborated model to distributions involving two distinct types of defects (bimodal distributions), fitting the estimated CFP of CVD-ZnS or CVD-ZnSe leads to a much improved description of the fracture process. In particular, the availability of two sets of statistical parameters (characteristic strength and shape parameter) can be taken advantage of for evaluating the failure-probability density, thus providing means of assessing the nature, the critical size, and the size distribution of the surface/subsurface flaws.
Generalized Weibull Linear Models
Andrea A. Prudente; Gauss M. Cordeiro
2010-01-01
For the first time, a new class of generalized Weibull linear models is introduced to be competitive to the well-known generalized (gamma and inverse Gaussian) linear models which are adequate for the analysis of positive continuous data. The proposed models have a constant coefficient of variation for all observations similar to the gamma models and may be suitable for a
Toshikazu Tasaki; Tso-Fu Mark Chang; Chiemi Ishiyama; Masato Sone
2011-01-01
Interfacial delamination mechanism between SU-8 micropillars with the widely change of aspect ratio and Si substrates was studied using Weibull distribution. Micropillars were fabricated by lithography on the substrate and delaminated from the substrate under bend loading. Delamination for aspect ratio of 1.4 and 2.2 with almost the same ?max indicates mode I fracture at interface and then shear stress
A practical and systematic review of Weibull statistics for reporting strengths of dental materials
Quinn, George D.; Quinn, Janet B.
2011-01-01
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. PMID:19945745
Estimating Weibull parameters for composite materials.
NASA Technical Reports Server (NTRS)
Robinson, E. Y.
1972-01-01
This paper deals with the statistical analysis of strength and fracture of materials in general, with application to fiber composites. The 'weakest link' model is considered in a fairly general form, and the resulting equations are demonstrated by using a Weibull distribution for flaws. This distribution appears naturally in a variety of problems, and therefore additional attention is devoted to analysis and statistical estimation connected with this distribution. Special working charts are included to facilitate interpretation of observed data and estimation of parameters. Implications of the size effect are considered for various kinds of flaw distributions. The paper describes failure and damage in a fiber-reinforced systems.
A delay metric for RC circuits based on the Weibull distribution
Frank Liu; Chandramouli V. Kashyap; Charles J. Alpert
2002-01-01
Physical design optimizations such as placement, interconnect synthesis, oorplanning, and routing require fast and accurate analysis of RC networks. Because of its simple close form and fast evaluation, the Elmore delay metric has been widely adopted. The recently proposed delay metrics PRIMO and H-gamma match the rst three circuit moments to the probability density function of a Gamma statistical distribution.
Jorge Cruz Fernandes; Pedro Miguel Amaral; Lu??s Guerra Rosa; Nobumitsu Shohoji
2000-01-01
Densified alumina ceramic disk specimens were prepared through sintering compacted alumina powders by concentrated solar beam in inert Ar gas atmosphere and their flexure breaking behaviour was evaluated by the ring-on-ring jig test under application of equibiaxial stress. Slope m of Weibull plot for MOR (modulus of rupture) values of these specimens was comparable to that of the reference alumina
Bojan Jankovic
2008-01-01
Abstact The procedure for the determination of density distribution functions of the apparent activation energies (ddfE\\u000a \\u000a a\\u000a s), for the nonisothermal decomposition process of sodium bicarbonate under a nitrogen atmosphere was established. It was\\u000a found that the experimental integral and differential conversion curves at different heating rates can be successfully described\\u000a by the nonisothermal Weibull distribution function (Wdf), in wide range
Weibull analysis of the biaxial fracture strength of a cast p-type LAST-T thermoelectric material
F. Ren; E. D. Case; E. J. Timm; M. D. Jacobs; H. J. Schock
2006-01-01
This is the first study applying Weibull statistics to the strength distribution of a thermoelectric (TE) material and to determine the fracture strength of a member of the LAST-T (lead–antimony–silver–tellurium–tin) family of high-temperature TE compounds. The p-type TE material Ag0.9Pb9Sn9Sb0.6Te20 was cast from the melt and specimens cut from the resulting ingot were fractured in a ball-on-ring biaxial fracture test.
Weibull analysis of the biaxial fracture strength of a cast p-type LAST-T thermoelectric material
F. Ren; E. D. Case; E. J. Timm; M. D. Jacobs; H. J. Schock
2006-01-01
This is the first study applying Weibull statistics to the strength distribution of a thermoelectric (TE) material and to determine the fracture strength of a member of the LAST-T (lead-antimony-silver-tellurium-tin) family of high-temperature TE compounds. The p-type TE material Ag0.9Pb9Sn9Sb0.6Te20 was cast from the melt and specimens cut from the resulting ingot were fractured in a ball-on-ring biaxial fracture test.
Bojan Jankovi?
2009-01-01
The degradation process of commercial grade Lexan® was investigated by thermogravimetric technique under isothermal experimental\\u000a conditions at four different operating temperatures: 375 °C, 387.5 °C, 400 °C and 425 °C. The kinetic triplet (E\\u000a \\u000a a\\u000a , A, f(?)) was determined using conventional and Weibull kinetic analysis. The applied kinetic procedure shows that the investigated\\u000a degradation process can be described by two-parameter autocatalytic Šesták–Berggren (SB)
NASA Technical Reports Server (NTRS)
Wheeler, J. T.
1990-01-01
The Weibull process, identified as the inhomogeneous Poisson process with the Weibull intensity function, is used to model the reliability growth assessment of the space shuttle main engine test and flight failure data. Additional tables of percentage-point probabilities for several different values of the confidence coefficient have been generated for setting (1-alpha)100-percent two sided confidence interval estimates on the mean time between failures. The tabled data pertain to two cases: (1) time-terminated testing, and (2) failure-terminated testing. The critical values of the three test statistics, namely Cramer-von Mises, Kolmogorov-Smirnov, and chi-square, were calculated and tabled for use in the goodness of fit tests for the engine reliability data. Numerical results are presented for five different groupings of the engine data that reflect the actual response to the failures.
Weibull analysis and flexural strength of hot-pressed core and veneered ceramic structures
Alvaro Della Bona; Kenneth J. Anusavice; Paul H. DeHoff
2003-01-01
Objective. To test the hypothesis that the Weibull moduli of single- and multilayer ceramics are controlled primarily by the structural reliability of the core ceramic.Methods. Seven groups of 20 bar specimens (25×4×1.2 mm) were made from the following materials: (1) IPS Empress®—a hot-pressed (HP) leucite-based core ceramic; (2) IPS Empress2®—a HP lithia-based core ceramic; (3 and 7) Evision®—a HP lithia-based
Reliability of the Weibull analysis of the strength of construction materials
Milan Ambrozic; Krunoslav Vidovic
2007-01-01
The breaking force during transversal loading of fibre-cement corrugated roofing sheets was measured on several test samples\\u000a from a serial production. The results were statistically analyzed assuming the 2-parameter Weibull statistics. In addition,\\u000a Monte Carlo statistical simulations were made by using a computerised built-in random-number generator. While smaller sample\\u000a data groups, mostly containing up to 50 samples, were studied in
NASA Astrophysics Data System (ADS)
Abas, Norzaida; Daud, Zalina M.; Yusof, Fadhilah
2014-11-01
A stochastic rainfall model is presented for the generation of hourly rainfall data in an urban area in Malaysia. In view of the high temporal and spatial variability of rainfall within the tropical rain belt, the Spatial-Temporal Neyman-Scott Rectangular Pulse model was used. The model, which is governed by the Neyman-Scott process, employs a reasonable number of parameters to represent the physical attributes of rainfall. A common approach is to attach each attribute to a mathematical distribution. With respect to rain cell intensity, this study proposes the use of a mixed exponential distribution. The performance of the proposed model was compared to a model that employs the Weibull distribution. Hourly and daily rainfall data from four stations in the Damansara River basin in Malaysia were used as input to the models, and simulations of hourly series were performed for an independent site within the basin. The performance of the models was assessed based on how closely the statistical characteristics of the simulated series resembled the statistics of the observed series. The findings obtained based on graphical representation revealed that the statistical characteristics of the simulated series for both models compared reasonably well with the observed series. However, a further assessment using the AIC, BIC and RMSE showed that the proposed model yields better results. The results of this study indicate that for tropical climates, the proposed model, using a mixed exponential distribution, is the best choice for generation of synthetic data for ungauged sites or for sites with insufficient data within the limit of the fitted region.
Methods and Example Case Study for Analysis of Variability and Uncertainty in
Frey, H. Christopher
Methods and Example Case Study for Analysis of Variability and Uncertainty in Emissions Estimation...................................................................... 11 2.2.4 Weibull Distribution.3.2 Lognormal Distribution ................................................................ 17 2.3.3 Weibull
FITTING WEIBULL AND LOGNORMAL DISTRIBUTIONS TO MEDIUM-DENSITY FIBERBOARD FIBER AND WOOD
70803-6202 (Received July 2005) ABSTRACT Fiber lengths were analyzed for random samples of medium, suitable statistical functions that can be used to accurately describe wood fiber length distribution over various fiber length regimes are still missing. For fiber dimension determination, the gen- eral
Li, Haijun
3-5.4: Weibull Distributions Math/Stat 370: Engineering Statistics Haijun Li lih@math.wsu.edu Department of Mathematics Washington State University Week 3 Haijun Li Math/Stat 370: Engineering Statistics N(µ, 2). µ = location parameter, = scale parameter. Haijun Li Math/Stat 370: Engineering Statistics
Modeling the reliability and maintenance costs of wind turbines using Weibull analysis
Vachon, W.A. [W.A. Vachon & Associates, Inc., Manchester, MA (United States)
1996-12-31
A general description is provided of the basic mathematics and use of Weibull statistical models for modeling component failures and maintenance costs as a function of time. The applicability of the model to wind turbine components and subsystems is discussed with illustrative examples of typical component reliabilities drawn from actual field experiences. Example results indicate the dominant role of key subsystems based on a combination of their failure frequency and repair/replacement costs. The value of the model is discussed as a means of defining (1) maintenance practices, (2) areas in which to focus product improvements, (3) spare parts inventory, and (4) long-term trends in maintenance costs as an important element in project cash flow projections used by developers, investors, and lenders. 6 refs., 8 figs., 3 tabs.
NASA Technical Reports Server (NTRS)
Shantaram, S. Pai; Gyekenyesi, John P.
1989-01-01
The calculation of shape and scale parametes of the two-parameter Weibull distribution is described using the least-squares analysis and maximum likelihood methods for volume- and surface-flaw-induced fracture in ceramics with complete and censored samples. Detailed procedures are given for evaluating 90 percent confidence intervals for maximum likelihood estimates of shape and scale parameters, the unbiased estimates of the shape parameters, and the Weibull mean values and corresponding standard deviations. Furthermore, the necessary steps are described for detecting outliers and for calculating the Kolmogorov-Smirnov and the Anderson-Darling goodness-of-fit statistics and 90 percent confidence bands about the Weibull distribution. It also shows how to calculate the Batdorf flaw-density constants by using the Weibull distribution statistical parameters. The techniques described were verified with several example problems, from the open literature, and were coded in the Structural Ceramics Analysis and Reliability Evaluation (SCARE) design program.
W. J. Padgett; S. D. Durham; A. M. Mason
1995-01-01
The single-filament test measurements for strength of carbon fibers obtained by Bader and Priest [5] are analyzed using a broader class of Weibull models with the scale parameter assumed to be a function of fiber gauge length. Two specific models are proposed for the fiber gauge length effect on tensile strength: The power law model and a linear model. The
The spokane heart study: weibull regression and coronary artery disease
Nairanjana Dasgupta; Peijin Xie; Monte O. Cheney; Lyle Broemeling; C. Harold Mielke Jr
2000-01-01
Coronary artery calcium is a marker of coronary artery disease and measures the progression of atherosclerosis. It is measured by electron beam computed tomography, and the measured amount of coronary artery calcium is highly skewed to the right and left censored. The distribution of coronary artery calcium appears to be Weibull. We propose a Weibull regression model and we analyze
Finite-size effects on return interval distributions for weakest-link-scaling systems
NASA Astrophysics Data System (ADS)
Hristopulos, Dionissios T.; Petrakis, Manolis P.; Kaniadakis, Giorgio
2014-05-01
The Weibull distribution is a commonly used model for the strength of brittle materials and earthquake return intervals. Deviations from Weibull scaling, however, have been observed in earthquake return intervals and the fracture strength of quasibrittle materials. We investigate weakest-link scaling in finite-size systems and deviations of empirical return interval distributions from the Weibull distribution function. Our analysis employs the ansatz that the survival probability function of a system with complex interactions among its units can be expressed as the product of the survival probability functions for an ensemble of representative volume elements (RVEs). We show that if the system comprises a finite number of RVEs, it obeys the ?-Weibull distribution. The upper tail of the ?-Weibull distribution declines as a power law in contrast with Weibull scaling. The hazard rate function of the ?-Weibull distribution decreases linearly after a waiting time ?c?n1/m, where m is the Weibull modulus and n is the system size in terms of representative volume elements. We conduct statistical analysis of experimental data and simulations which show that the ? Weibull provides competitive fits to the return interval distributions of seismic data and of avalanches in a fiber bundle model. In conclusion, using theoretical and statistical analysis of real and simulated data, we demonstrate that the ?-Weibull distribution is a useful model for extreme-event return intervals in finite-size systems.
Finite-size effects on return interval distributions for weakest-link-scaling systems.
Hristopulos, Dionissios T; Petrakis, Manolis P; Kaniadakis, Giorgio
2014-05-01
The Weibull distribution is a commonly used model for the strength of brittle materials and earthquake return intervals. Deviations from Weibull scaling, however, have been observed in earthquake return intervals and the fracture strength of quasibrittle materials. We investigate weakest-link scaling in finite-size systems and deviations of empirical return interval distributions from the Weibull distribution function. Our analysis employs the ansatz that the survival probability function of a system with complex interactions among its units can be expressed as the product of the survival probability functions for an ensemble of representative volume elements (RVEs). We show that if the system comprises a finite number of RVEs, it obeys the ?-Weibull distribution. The upper tail of the ?-Weibull distribution declines as a power law in contrast with Weibull scaling. The hazard rate function of the ?-Weibull distribution decreases linearly after a waiting time ?(c) ? n(1/m), where m is the Weibull modulus and n is the system size in terms of representative volume elements. We conduct statistical analysis of experimental data and simulations which show that the ? Weibull provides competitive fits to the return interval distributions of seismic data and of avalanches in a fiber bundle model. In conclusion, using theoretical and statistical analysis of real and simulated data, we demonstrate that the ?-Weibull distribution is a useful model for extreme-event return intervals in finite-size systems. PMID:25353774
Weibull analysis of strength-length relationships in single Nicalon SiC fibres
H. F. Wu; A. N. Netrwavali
1992-01-01
Nicalon SiC fibre is naturally brittle and offers high-temperature application in fibrous composites. Due to the randomly distributed flaws along the fibre, the statistical variability in single-fibre strength is obvious. In this paper, the effect of heat-cleaning procedures on Nicalon fibres has been investigated, and the statistical strength and variability of single Nicalon fibres have been characterized in tension and
Transformation of the bathtub failure rate data in reliability for using Weibull-model analysis
Govind S. Mudholkar; Kobby O. Asubonteng; Alan D. Hutson
2009-01-01
All statistical methods involve basic model assumptions, which if violated render results of the analysis dubious. A solution to such a contingency is to seek an appropriate model or to modify the customary model by introducing additional parameters. Both of these approaches are in general cumbersome and demand uncommon expertise. An alternative is to transform the data to achieve compatibility
A. Nevarez-Rascon; A. Aguilar-Elguezabal; E. Orrantia; M. H. Bocanegra-Bernal
2011-01-01
The aim of this investigation was to study the variability in compressive strength, fracture toughness and microhardness applying the well-known Weibull statistics and to be able to provide a wide spectrum of mechanical properties in Al2O3 whisker reinforced alumina toughened zirconia (ATZ) and zirconia toughened alumina (ZTA) nanocomposites for possible dental applications. Uniaxial compression tests at room temperature of samples
Channel Capacity and Second-Order Statistics in Weibull Fading
Nikos C. Sagias; Dimitris A. Zogas; George K. Karagiannidis; George S. Tombras
2004-01-01
The second-order statistics and the channel capacity of the Weibull fading channel are studied. Exact closed-form expressions are derived for the average level crossing rate, the average fade duration, as well as the average Shannon's channel capacity of the Weibull fading process. Numerical results are presented to illustrate the proposed mathematical analysis and to examine the effects of the fading
Harris, S.; Gross, R.; Mitchell, E.
2011-01-18
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.
Boyer, Edmond
, and a Weibull modulus of 5. AFM image analysis and mechanical analysis are complementary means of measurement défauts sur fibre de verre par AFM et traction sur fil Comparative fiber defect size distribution analysis une contrainte à la rupture de 1400 MPa et un module de Weibull de 10. La fibre HD a par contre une
Weibull crack density coefficient for polydimensional stress states
NASA Technical Reports Server (NTRS)
Gross, Bernard; Gyekenyesi, John P.
1989-01-01
A structural ceramic analysis and reliability evaluation code has recently been developed encompassing volume and surface flaw induced fracture, modeled by the two-parameter Weibull probability density function. A segment of the software involves computing the Weibull polydimensional stress state crack density coefficient from uniaxial stress experimental fracture data. The relationship of the polydimensional stress coefficient to the uniaxial stress coefficient is derived for a shear-insensitive material with a random surface flaw population.
Gas turbine safety improvement through risk analysis
Crosby, T.M.; Reinman, G.L.
1987-01-01
This paper provides certain statistical methods that are used to improve system safety. It provides an understanding of Weibull analysis, in that it describes when the Weibull distribution is appropriate, how to construct a Weibull plot, and how to use the parameters of the Weibull distribution to calculate risk. This paper also provides the engineer with a comprehension of Monte Carlo simulation as it relates to quantifying safety risk. The basic components of Monte Carlo simulation are discussed as well as the formulation of a system model and its application in the gas turbine industry.
Gas turbine safety improvement through risk analysis
Crosby, T.M.; Reinman, G.L.
1988-04-01
This paper is intended to provide the engineer with the information necessary to understand certain statistical methods that are used to improve system safety. It will provide an understanding of Weibull analysis, in that it describes when the Weibull distribution is appropriate, how to construct a Weibull plot, and how to use the parameters of the Weibull distribution to calculate risk. The paper will also provide the engineer with a comprehension of Monte Carlo simulation as it relates to quantifying safety risk. The basic components of Monte Carlo simulation are discussed as well as the formulation of a system model and its application in the gas turbine industry.
Performance Sampling and Weibull Distributions.
ERIC Educational Resources Information Center
March, James C.; March, James G.
1981-01-01
Concerning their study of Wisconsin school superintendents, the authors comment briefly on small differences between their own tactics for modeling mobility and the tactics used by some others, including Schmittlein and Morrison. (Author/MLF)
NASA Astrophysics Data System (ADS)
Sheng, Dong; Fengli, Li; Guiying, Jiao
2003-04-01
Hydrologic frequency analysis plays an important role in coastal and ocean engineering for structural design and disaster prevention in coastal areas. This paper proposes a Nonlinear Least Squares Method (NLSM), which estimates the three unknown parameters of the Weibull distribution simultaneously by an iteration method. Statistical test shows that the NLSM fits each data sample well. The effects of different parameter-fitting methods, distribution models, and threshold values are also discussed in the statistical analysis of storm set-down elevation. The best-fitting probability distribution is given and the corresponding return values are estimated for engineering design.
A Weibull characterization for tensile fracture of multicomponent brittle fibers
NASA Technical Reports Server (NTRS)
Barrows, R. G.
1977-01-01
Necessary to the development and understanding of brittle fiber reinforced composites is a means to statistically describe fiber strength and strain-to-failure behavior. A statistical characterization for multicomponent brittle fibers is presented. The method, which is an extension of usual Weibull distribution procedures, statistically considers the components making up a fiber (e.g., substrate, sheath, and surface) as separate entities and taken together as in a fiber. Tensile data for silicon carbide fiber and for an experimental carbon-boron alloy fiber are evaluated in terms of the proposed multicomponent Weibull characterization.
Weibull modeling of particle cracking in metal matrix composites
Lewis, C.A.; Withers, P.J. [Univ. of Cambridge (United Kingdom). Dept. of Materials Science and Metallurgy] [Univ. of Cambridge (United Kingdom). Dept. of Materials Science and Metallurgy
1995-10-01
An investigation into the occurrence of reinforcement cracking within a particulate ZrO{sub 2}/2618 Al alloy metal matrix composite under tensile plastic straining has been carried out, special attention being paid to the dependence of fracture on particle size and shape. The probability of particle cracking has been modeled using a Weibull approach, giving good agreement with the experimental data. Values for the Weibull modulus and the stress required to crack the particles were found to be within the range expected for the cracking of ceramic particles. Additional information regarding the fracture behavior of the particles was provided by in-situ neutron diffraction monitoring of the internal strains, measurement of the variation in the composite Young`s modulus with straining and by direct observation of the cracked particles. The values of the particle stress required for the initiation of particle cracking deduced from these supplementary experiments were found to be in good agreement with each other and with the results from the Weibull analysis. Further, it is shown that while both the current experiments, as well as the previous work of others, can be well described by the Weibull approach, the exact values of the Weibull parameters do deduced are very sensitive to the approximations and the assumptions made in constructing the model.
NASA Astrophysics Data System (ADS)
Williams, Mike; Egede, Ulrik; Paterson, Stuart; LHCb Collaboration
2011-12-01
The distributed analysis experience to date at LHCb has been positive: job success rates are high and wait times for high-priority jobs are low. LHCb users access the grid using the GANGA job-management package, while the LHCb virtual organization manages its resources using the DIRAC package. This clear division of labor has benefitted LHCb and its users greatly; it is a major reason why distributed analysis at LHCb has been so successful. The newly formed LHCb distributed analysis support team has also proved to be a success.
Distributed Analysis using ASAP
C Munro; J Andreev; J Herrala; O Kodolova; A Khan
ASAP is a system for enabling distributed analysis for CMS physicists. It was created with the aim of simplifying the transition from a locally running application to one that is distributed across the Grid. The experience gained in operating the system for the past two years has been used to redevelop a more robust, performant and scalable version. ASAP consists
Quantitative Analysis of Variability and Uncertainty in Environmental Data and Models
Frey, H. Christopher
Quantitative Analysis of Variability and Uncertainty in Environmental Data and Models Volume 1 ........................................6 1.3 Is A Probabilistic Analysis Necessary ...................................................................................13 2.1.4 Weibull Distribution
Time Series Analysis of Particle Tracking Data for Molecular Motion on the Cell Membrane
Huerta, Gabriel
Time Series Analysis of Particle Tracking Data for Molecular Motion on the Cell Membrane Wenxia.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.2 Preliminary Analysis of the Jumps 16 3.1 The General Weibull Distribution . . . . . . . . . . . . . . . . . . . . . . . . 19 3
Impact of Three-Parameter Weibull Models in Probabilistic Assessment of Earthquake Hazards
NASA Astrophysics Data System (ADS)
Pasari, Sumanta; Dikshit, Onkar
2014-07-01
This paper investigates the suitability of a three-parameter (scale, shape, and location) Weibull distribution in probabilistic assessment of earthquake hazards. The performance is also compared with two other popular models from same Weibull family, namely the two-parameter Weibull model and the inverse Weibull model. A complete and homogeneous earthquake catalog ( Yadav et al. in Pure Appl Geophys 167:1331-1342, 2010) of 20 events ( M ? 7.0), spanning the period 1846 to 1995 from north-east India and its surrounding region (20°-32°N and 87°-100°E), is used to perform this study. The model parameters are initially estimated from graphical plots and later confirmed from statistical estimations such as maximum likelihood estimation (MLE) and method of moments (MoM). The asymptotic variance-covariance matrix for the MLE estimated parameters is further calculated on the basis of the Fisher information matrix (FIM). The model suitability is appraised using different statistical goodness-of-fit tests. For the study area, the estimated conditional probability for an earthquake within a decade comes out to be very high (?0.90) for an elapsed time of 18 years (i.e., 2013). The study also reveals that the use of location parameter provides more flexibility to the three-parameter Weibull model in comparison to the two-parameter Weibull model. Therefore, it is suggested that three-parameter Weibull model has high importance in empirical modeling of earthquake recurrence and seismic hazard assessment.
Bass, B.R.; McAfee, W.J.; Williams, P.T.
1999-08-01
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.
Electromagnetic analysis of nanostructure dispersion in polymer matrices
Pfeifer, Steven Charles; Pfeifer, Steven Charles
2012-01-01
Analysis of electrical percolation thresholds in carbon nanotube networks using the WeibullAnalysis of electrical percolation thresholds in carbon nanotube networks, using the WeibullAnalysis of electrical percolation thresholds in carbon nanotube networks using the Weibull
Non-parametric texture defect detection using Weibull features
NASA Astrophysics Data System (ADS)
Timm, Fabian; Barth, Erhardt
2011-03-01
The detection of abnormalities is a very challenging problem in computer vision, especially if these abnormalities must be detected in images of textured surfaces such as textile, stone, or wood. We propose a novel, non-parametric approach for defect detection in textures that only employs two features. We compute the two parameters of a Weibull fit for the distribution of image gradients in local regions. Then, we perform a simple novelty detection algorithm in order to detect arbitrary deviations of the reference texture. Therefore, we evaluate the Euclidean distances of all local patches to a reference point in the Weibull space, where the reference point is determined for each texture image individually. Thus, our approach becomes independent of the particular texture type and also independent of a certain defect type. For performance evaluation we use the highly challenging database provided by Bosch for a contest on industrial optical inspection with different classes of textures and different defect types. By using the Weibull parameters we can detect local deviations of texture images in an unsupervised manner with high accuracy. Compared to existing approaches such as Gabor filters or grey level statistics, our approach is not only powerful, but also very efficient such that it can also be applied for real-time applications.
NASA Astrophysics Data System (ADS)
Barrios, Ricardo; Dios, Federico
2012-10-01
Recently a new proposal to model the fading channel in free-space optical links, namely, the exponentiated Weibull (EW) distribution, has been made. It has been suggested that the EW distribution can model the probability density function (PDF) of the irradiance under weak-to-strong conditions in the presence of aperture averaging. Here, we carry out an analysis of probability of fade and bit error-rate (BER) performance using simulation results and experimental data. The BER analysis assumes intensity modulation/direct detection with on-off keying, and new expressions are derived. Data is modeled following the statistics of the EW fading channel model, and compared with the Gamma-Gamma and Lognormal distributions, as the most widely accepted models nowadays. It is shown how the proposed EW model is valid in all the tested conditions, and even outperforms the GG and LN distributions, that are only valid under certain scenarios.
Munro, Craig; Khan, Akram
2007-01-01
ASAP is a job creation and management framework used by CMS physicists to perform data analysis using the Grid. ASAP hides many of the low-level details of the Grid so that physicists can distribute their work across the Grid to take advantage of the available CPU power and access the stored data. There is also a server side component to, which users can delegate responsibility for their jobs. The server monitors the status of jobs and resubmits in the case of Grid or application failure The Grid provides the computing and storage resources necessary for the analysis and storage of large volumes of High Energy Physics data. ASAP provides a layer over the standard grid job management tools, which means that users do not have to be concerned with the details of job creation, submission and monitoring. The presence of the server side component increases the chances of the users’ jobs being successfully completed. The main concerns are the performance and reliability of jobs. In addition documentation is often ...
Reachability Analysis on Distributed Executions
Claire Diehl; Claude Jard; Jean-xavier Rampon
1993-01-01
The paper presents basic algorithms for trace checking of distributed programs. In distributed systems, detecting global properties requires a careful analysis of the causal structure of the execution. Based on the on-the-fly observation of the partial order of message causality, we show how to build the lattice of all the reachable states of the distributed system under test. The regular
Weibull- k Revisited: "Tall" Profiles and Height Variation of Wind Statistics
NASA Astrophysics Data System (ADS)
Kelly, Mark; Troen, Ib; Jørgensen, Hans E.
2014-07-01
The Weibull distribution is commonly used to describe climatological wind-speed distributions in the atmospheric boundary layer. While vertical profiles of mean wind speed in the atmospheric boundary layer have received significant attention, the variation of the shape of the wind distribution with height is less understood. Previously we derived a probabilistic model based on similarity theory for calculating the effects of stability and planetary boundary-layer depth upon long-term mean wind profiles. However, some applications (e.g. wind energy estimation) require the Weibull shape parameter ( k), as well as mean wind speed. Towards the aim of improving predictions of the Weibull- profile, we develop expressions for the profile of long-term variance of wind speed, including a method extending our probabilistic wind-profile theory; together these two profiles lead to a profile of Weibull-shape parameter. Further, an alternate model for the vertical profile of Weibull shape parameter is made, improving upon a basis set forth by Wieringa (Boundary-Layer Meteorol, 1989, Vol. 47, 85-110), and connecting with a newly-corrected corollary of the perturbed geostrophic-drag theory of Troen and Petersen (European Wind Atlas, 1989, Risø National Laboratory, Roskilde). Comparing the models for Weibull- k profiles, a new interpretation and explanation is given for the vertical variation of the shape of wind-speed distributions. Results of the modelling are shown for a number of sites, with a discussion of the models' efficacy and applicability. The latter includes a comparative evaluation of Wieringa-type empirical models and perturbed-geostrophic forms with regard to surface-layer behaviour, as well as for heights where climatological wind-speed variability is not dominated by surface effects.
Transmission overhaul and replacement predictions using Weibull and renewal theory
NASA Technical Reports Server (NTRS)
Savage, M.; Lewicki, D. G.
1989-01-01
A method to estimate the frequency of transmission overhauls is presented. This method is based on the two-parameter Weibull statistical distribution for component life. A second method is presented to estimate the number of replacement components needed to support the transmission overhaul pattern. The second method is based on renewal theory. Confidence statistics are applied with both methods to improve the statistical estimate of sample behavior. A transmission example is also presented to illustrate the use of the methods. Transmission overhaul frequency and component replacement calculations are included in the example.
Transmission overhaul and replacement predictions using Weibull and renewel theory
NASA Technical Reports Server (NTRS)
Savage, M.; Lewicki, D. G.
1989-01-01
A method to estimate the frequency of transmission overhauls is presented. This method is based on the two-parameter Weibull statistical distribution for component life. A second method is presented to estimate the number of replacement components needed to support the transmission overhaul pattern. The second method is based on renewal theory. Confidence statistics are applied with both methods to improve the statistical estimate of sample behavior. A transmission example is also presented to illustrate the use of the methods. Transmission overhaul frequency and component replacement calculations are included in the example.
The distribution of first-passage times and durations in FOREX and future markets
NASA Astrophysics Data System (ADS)
Sazuka, Naoya; Inoue, Jun-ichi; Scalas, Enrico
2009-07-01
Possible distributions are discussed for intertrade durations and first-passage processes in financial markets. The view-point of renewal theory is assumed. In order to represent market data with relatively long durations, two types of distributions are used, namely a distribution derived from the Mittag-Leffler survival function and the Weibull distribution. For the Mittag-Leffler type distribution, the average waiting time (residual life time) is strongly dependent on the choice of a cut-off parameter tmax, whereas the results based on the Weibull distribution do not depend on such a cut-off. Therefore, a Weibull distribution is more convenient than a Mittag-Leffler type if one wishes to evaluate relevant statistics such as average waiting time in financial markets with long durations. On the other hand, we find that the Gini index is rather independent of the cut-off parameter. Based on the above considerations, we propose a good candidate for describing the distribution of first-passage time in a market: The Weibull distribution with a power-law tail. This distribution compensates the gap between theoretical and empirical results more efficiently than a simple Weibull distribution. It should be stressed that a Weibull distribution with a power-law tail is more flexible than the Mittag-Leffler distribution, which itself can be approximated by a Weibull distribution and a power-law. Indeed, the key point is that in the former case there is freedom of choice for the exponent of the power-law attached to the Weibull distribution, which can exceed 1 in order to reproduce decays faster than possible with a Mittag-Leffler distribution. We also give a useful formula to determine an optimal crossover point minimizing the difference between the empirical average waiting time and the one predicted from renewal theory. Moreover, we discuss the limitation of our distributions by applying our distribution to the analysis of the BTP future and calculating the average waiting time. We find that our distribution is applicable as long as durations follow a Weibull law for short times and do not have too heavy a tail.
Measuring the Weibull modulus of microscope slides
NASA Technical Reports Server (NTRS)
Sorensen, Carl D.
1992-01-01
The objectives are that students will understand why a three-point bending test is used for ceramic specimens, learn how Weibull statistics are used to measure the strength of brittle materials, and appreciate the amount of variation in the strength of brittle materials with low Weibull modulus. They will understand how the modulus of rupture is used to represent the strength of specimens in a three-point bend test. In addition, students will learn that a logarithmic transformation can be used to convert an exponent into the slope of a straight line. The experimental procedures are explained.
Performance Analysis with Truncated Heavy-Tailed Distributions
Søren Asmussen; Mats Pihlsgård
2005-01-01
This paper deals with queues and insurance risk processes where a generic service time, resp. generic claim, has the form\\u000a U ? K for some r.v. U with distribution B which is heavy-tailed, say Pareto or Weibull, and a typically large K, say much larger than \\u000a $$\\\\mathbb{E}U$$\\u000a . We study the compound Poisson ruin probability ?(u) or, equivalently, the tail
Strength analysis of yttria-stabilized tetragonal zirconia polycrystals
Noguchi, K.; Matsuda, Y.; Oishi, M. (Toray Research Center, Inc., Otsu, Shiga 520 (JP)); Masaki, T.; Nakayama, S.; Mizushina, M. (Toray Industries, Inc., Otsu, Shiga 520 (JP))
1990-09-01
This paper reports the tensile strength of Y{sub 2}O{sub 3}-stabilized ZrO{sub 2} polycrystals (Y-TZP) measured by a newly developed tensile testing method with a rectangular bar. The tensile strength of Y-TZP was lower than that of the three-point bend strength, and the shape of the tensile strength distribution was quite different from that of the three-point bend strength distribution. It was difficult to predict the distribution curve of the tensile strength using the data of the three-point bend strength by one-modal Weibull distribution. The distribution of the tensile strength was analyzed by two- or three-modal Weibull distribution coupled with an analysis of fracture origins. The distribution curve of the three-point bend strength which was estimated by multimodal Weibull distribution agreed favorably with that of the measured three-point bend strength values. A two-modal Weibull distribution function was formulated approximately from the distributions of the tensile and three-point bend strengths, and the estimated two-modal Weibull distribution function for the four-point bend strength agreed well with the measured four-point bend strength.
Incorporating finite element analysis into component life and reliability
NASA Technical Reports Server (NTRS)
August, Richard; Zaretsky, Erwin V.
1991-01-01
A method for calculating a component's design survivability by incorporating finite element analysis and probabilistic material properties was developed. The method evaluates design parameters through direct comparisons of component survivability expressed in terms of Weibull parameters. The analysis was applied to a rotating disk with mounting bolt holes. The highest probability of failure occurred at, or near, the maximum shear stress region of the bolt holes. Distribution of failure as a function of Weibull slope affects the probability of survival. Where Weibull parameters are unknown for a rotating disk, it may be permissible to assume Weibull parameters, as well as the stress-life exponent, in order to determine the disk speed where the probability of survival is highest.
Analysis of Voltage Rise Effect on Distribution Network with Distributed
Pota, Himanshu Roy
Analysis of Voltage Rise Effect on Distribution Network with Distributed Generation M. A. Mahmud.hossain@adfa.edu.au, and H.Pota@adfa.edu.au). Abstract: Connections of distributed generation (DG) in distribution networks are increasing. These connections of distributed generation cause voltage rise in the distribution network
Effect of Individual Component Life Distribution on Engine Life Prediction
NASA Technical Reports Server (NTRS)
Zaretsky, Erwin V.; Hendricks, Robert C.; Soditus, Sherry M.
2003-01-01
The effect of individual engine component life distributions on engine life prediction was determined. A Weibull-based life and reliability analysis of the NASA Energy Efficient Engine was conducted. The engine s life at a 95 and 99.9 percent probability of survival was determined based upon the engine manufacturer s original life calculations and assumed values of each of the component s cumulative life distributions as represented by a Weibull slope. The lives of the high-pressure turbine (HPT) disks and blades were also evaluated individually and as a system in a similar manner. Knowing the statistical cumulative distribution of each engine component with reasonable engineering certainty is a condition precedent to predicting the life and reliability of an entire engine. The life of a system at a given reliability will be less than the lowest-lived component in the system at the same reliability (probability of survival). Where Weibull slopes of all the engine components are equal, the Weibull slope had a minimal effect on engine L(sub 0.1) life prediction. However, at a probability of survival of 95 percent (L(sub 5) life), life decreased with increasing Weibull slope.
Statistical Analysis of EXTREMES in GEOPHYSICS
Gilleland, Eric
-point at µ - ). · Weibull (upper end-point at µ - ). #12;Statistical AnalysisStatistical Analysis of EXTREMES in GEOPHYSICS Zwiers FW and Kharin VV. 1998. Changes;Statistical Analysis of Averages Central Limit Theorem: X1, . . . , Xn random sample from any distribution. X1
Original article A Bayesian analysis
Boyer, Edmond
Original article A Bayesian analysis of mixed survival modelst V Ducrocq1 G Casella2 1 Department the parameters T of the distribution of frailty terms, a Bayesian analysis is proposed. Inferences are drawn from, Weibull), where the frailty terms are correlated through a known relationship matrix, or in more general
Statistical Analysis of Environment Canada's Wind Speed Data
Taylor, James H.
Statistical Analysis of Environment Canada's Wind Speed Data Someshwar Singh Department markets. Time-series models which are indirectly based on a Weibull Distribution (WD) are used extensively. It is shown through statistical analysis that the hourly prediction error distributions are nearly Gaussian
NASA Astrophysics Data System (ADS)
Chen, Chien-Chih; Tseng, Chih-Yuan; Telesca, Luciano; Chi, Sung-Ching; Sun, Li-Chung
2012-02-01
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.
Survival extrapolation using the poly-Weibull model
Lunn, David; Sharples, Linda D
2015-01-01
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
Survival extrapolation using the poly-Weibull model.
Demiris, Nikolaos; Lunn, David; Sharples, Linda D
2015-04-01
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
Analysis of the KW Distribution Using a Generalization of the MEIJER’S G-Function
NASA Astrophysics Data System (ADS)
Krasznovszky, S.
With the aid of the H-function of Fox we calculate the characteristic function of the Krasznovszky-Wagner(KW) distribution and the distributions of products, quotients and powers of independent KW-function variates. The KW distribution includes as special cases many of classical distributions, e.g., the exponential, the gamma, the chi-square the Weibull, as well as some others which appear in physics. Several examples in connection with statistics and KNO scaling are given.
Aerospace Applications of Weibull and Monte Carlo Simulation with Importance Sampling
NASA Technical Reports Server (NTRS)
Bavuso, Salvatore J.
1998-01-01
Recent developments in reliability modeling and computer technology have made it practical to use the Weibull time to failure distribution to model the system reliability of complex fault-tolerant computer-based systems. These system models are becoming increasingly popular in space systems applications as a result of mounting data that support the decreasing Weibull failure distribution and the expectation of increased system reliability. This presentation introduces the new reliability modeling developments and demonstrates their application to a novel space system application. The application is a proposed guidance, navigation, and control (GN&C) system for use in a long duration manned spacecraft for a possible Mars mission. Comparisons to the constant failure rate model are presented and the ramifications of doing so are discussed.
B. G. Kumaraswamy; B. K. Keshavan; Y. T. Ravikiran
2011-01-01
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.
A Weibull brittle material failure model for the ABAQUS computer program
Bennett, J.
1991-08-01
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 by a user subroutine for ABAQUS. Example problems illustrating the capability and accuracy of the model are given. 24 refs., 12 figs.
Hirose, H
1997-01-01
This paper proposes a new treatment for electrical insulation degradation. Some types of insulation which have been used under various circumstances are considered to degrade at various rates in accordance with their stress circumstances. The cross-linked polyethylene (XLPE) insulated cables inspected by major Japanese electric companies clearly indicate such phenomena. By assuming that the inspected specimen is sampled from one of the clustered groups, a mixed degradation model can be constructed. Since the degradation of the insulation under common circumstances is considered to follow a Weibull distribution, a mixture model and a Weibull power law can be combined. This is called The mixture Weibull power law model. By using the maximum likelihood estimation for the newly proposed model to Japanese 22 and 33 kV insulation class cables, they are clustered into a certain number of groups by using the AIC and the generalized likelihood ratio test method. The reliability of the cables at specified years are assessed. PMID:9384621
A Weibull multi-state model for the dependence of progression-free survival and overall survival.
Li, Yimei; Zhang, Qiang
2015-07-30
In oncology clinical trials, overall survival, time to progression, and progression-free survival are three commonly used endpoints. Empirical correlations among them have been published for different cancers, but statistical models describing the dependence structures are limited. Recently, Fleischer et al. proposed a statistical model that is mathematically tractable and shows some flexibility to describe the dependencies in a realistic way, based on the assumption of exponential distributions. This paper aims to extend their model to the more flexible Weibull distribution. We derived theoretical correlations among different survival outcomes, as well as the distribution of overall survival induced by the model. Model parameters were estimated by the maximum likelihood method and the goodness of fit was assessed by plotting estimated versus observed survival curves for overall survival. We applied the method to three cancer clinical trials. In the non-small-cell lung cancer trial, both the exponential and the Weibull models provided an adequate fit to the data, and the estimated correlations were very similar under both models. In the prostate cancer trial and the laryngeal cancer trial, the Weibull model exhibited advantages over the exponential model and yielded larger estimated correlations. Simulations suggested that the proposed Weibull model is robust for data generated from a range of distributions. Copyright © 2015 John Wiley & Sons, Ltd. PMID:25865438
Distributed Data Analysis in ATLAS
Nilsson, P; The ATLAS collaboration
2012-01-01
Data analysis using grid resources is one of the fundamental challenges to be addressed before the start of LHC data taking. The ATLAS detector will produce petabytes of data per year, and roughly one thousand users will need to run physics analyses on this data. Appropriate user interfaces and helper applications have been made available to ensure that the grid resources can be used without requiring expertise in grid technology. These tools enlarge the number of grid users from a few production administrators to potentially all participating physicists. ATLAS makes use of three grid infrastructures for the distributed analysis: the EGEE sites, the Open Science Grid, and NorduGrid. These grids are managed by the gLite workload management system, the PanDA workload management system, and ARC middleware; many sites can be accessed via both the gLite WMS and PanDA. Users can choose between two front-end tools to access the distributed resources. Ganga is a tool co-developed with LHCb to provide a common interfa...
Spatial and Temporal Patterns of Global Onshore Wind Speed Distribution
Zhou, Yuyu; Smith, Steven J.
2013-09-09
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/CFSR reanalysis data. The estimated Weibull distribution performs well in fitting the time series wind speed data at the global level according to R2, root mean square error, and power density error. The spatial, decadal, and seasonal patterns of wind speed distribution were then evaluated. 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 substantial errors. While large-scale wind speed data is often presented in the form of average wind speeds, these results highlight the need to also provide information on the wind speed distribution.
Comparison of Weibull strength parameters from flexure and spin tests of brittle materials
NASA Technical Reports Server (NTRS)
Holland, Frederic A., Jr.; Zaretsky, Erwin V.
1991-01-01
Fracture data from five series of four point bend tests of beam and spin tests of flat annular disks were reanalyzed. Silicon nitride and graphite were the test materials. The experimental fracture strengths of the disks were compared with the predicted strengths based on both volume flaw and surface flaw analyses of four point bend data. Volume flaw analysis resulted in a better correlation between disks and beams in three of the five test series than did surface flaw analysis. The Weibull (moduli) and characteristic gage strengths for the disks and beams were also compared. Differences in the experimental Weibull slopes were not statistically significant. It was shown that results from the beam tests can predict the fracture strength of rotating disks.
University of Delaware Technical Analysis for On-Site Wind Generation
Firestone, Jeremy
Rose and Weibull Distribution 12 #12;Final Report Technical Analysis for On-site Wind GenerationUniversity of Delaware Technical Analysis for On-Site Wind Generation Prepared by: Sustainable Energy Developments, Inc. Tuesday, May 19, 2009 #12;Final Report Technical Analysis for On-site Wind
Analysis of Failures Characteristics in the UNINETT IP Backbone Network
Nørvåg, Kjetil
Analysis of Failures Characteristics in the UNINETT IP Backbone Network Andr´es J. Gonz-known distributions. We observe that the Weibull assumption that is traditionally used to model link failures that interval availability analysis has on SLAs under unprotected and shared protected connections, assuming
Sampling for tree-ring analysis Oscar Garcia
García, Oscar
Sampling for tree-ring analysis Oscar Garc´ia Forest Research Institute Rotorua, New Zealand Abstract Tree-ring analysis can be used to estimate growth in forest inven- tory, and to supplement as a method based on order statistics from the Weibull distribution. Best results were obtained
Analysis of Hybrid Censored Competing Shrijita Bhattacharya 1
Kundu, Debasis
Analysis of Hybrid Censored Competing Risks Data Shrijita Bhattacharya 1 , Biswabrata Pradhan1 & Debasis Kundu2 Abstract In this paper we consider analysis of hybrid censored competing risks data, based causes of failure follow Weibull distribution with the same shape parameter, but different scale
GRB brightness ratio distribution analysis
NASA Astrophysics Data System (ADS)
Laros, J. G.
1996-08-01
The objective of this analysis is to obtain insight into whether positionally close pairs of GRBs are due to repetitions, clustering, or random chance. We consider the Brightness Ratio Distribution (BRD) of pairs of events. Here, brightness is used as a generic term for any quantity related to the observed intensity of an event. The BRD has the interesting property that if one can select pairs whose components are at the same distance-such as, by considering only close-together pairs-then the distance dependence ``drops out'' of each brightness ratio and the BRD becomes narrower because its width no longer has a component caused by the sources' differing distances. We have begun to apply this analysis to the BATSE events for which location and brightness data are available, comparing the BRD for close-together event pairs to the BRDs for the other (presumedly unrelated) pairs. Preliminary results do not show any clear indication that close-together pairs are related. However, this work is at a very early stage with regard to optimizing the method and understanding its properties.
Bayesian Analysis for Partially Complete Time and Type of Failure Data
Kundu, Debasis
Bayesian Analysis for Partially Complete Time and Type of Failure Data Debasis Kundu Abstract In this paper we consider the Bayesian analysis of competing risks data, when the data are partially complete Weibull distributions with the common shape parameter but different scale parameters. When the shape
Fault analysis on distribution feeders with distributed generators
Mesut E. Baran; I. El-Markaby
2005-01-01
This paper shows that the current an inverter interfaced distributed generator (IIDG) contributes to a fault varies considerably, due mainly to fast response of its controller. This paper proposes a method to extend the conventional fault analysis methods so that IIDG contribution can be estimated in the fault analysis. The proposed method gives rms profiles of the fault currents of
Peampring, Chaimongkon; Sanohkan, Sasiwimol
2014-12-01
To evaluate the durability of machinable dental restorative materials, this study performed an experiment to evaluate the flexural strength and Weibull statistics of a machinable lithium disilicate glass-ceramic and a machinable composite resin after being thermocycled for certain cycles. A total of 40 bar-shape specimens of were prepared with the dimension of 20 mm × 4 mm × 2 mm, which were divided into four groups of 10 specimens. Ten specimens of machinable lithium disilicate glass-ceramic (IPS e.max CAD, Ivoclar Vivadent, Liechtenstein) and 10 specimens of machinable composite resin (Paradigm MZ 100, 3M ESPE, USA) were subjected to 3-point flexural strength test. Other 10 specimens of each material were thermocycled between water temperature of 5 and 55 °C for 10,000 cycles. After that, they were tested using 3-point flexural strength test. Statistical analysis was performed using two-way analysis of variance and Tukey multiple comparisons. Weibull analysis was performed to evaluate the reliability of the strength. Means of strength and their standard deviation were: thermocycled IPS e.max CAD 389.10 (50.75), non-thermocycled IPS e.max CAD 349.96 (38.34), thermocycled Paradigm MZ 100 157.51 (12.85), non-thermocycled Paradigm MZ 100 153.33 (19.97). Within each material group, there was no significant difference in flexural strength between thermocycled and non-thermocycled specimens. Considering the Weibull analysis, there was no statistical difference of Weibull modulus in all experimental groups. Within the limitation of this study, the results showed that there was no significant effect of themocycling on flexural strength and Weibull modulus of a machinable glass-ceramic and a machinable composite resin. PMID:25489161
Statistical analysis of bubble and crystal size distributions: Formulations and procedures
NASA Astrophysics Data System (ADS)
Proussevitch, Alexander A.; Sahagian, Dork L.; Tsentalovich, Evgeni P.
2007-07-01
Bubble and crystal size distributions have previously been described only by either exponential or power law functions. Within this limited framework, it has not been possible to characterize size distributions in a fully quantitative manner. We have developed an analytical and computational formulation with which to characterize and study crystal and bubble size distributions (BSD). This formulation demonstrates that all distributions known to date belong to the logarithmic family of statistical distributions. Four functions within the logarithmic family are best suited to natural bubbles and crystals (log normal, logistic, Weibull, and exponential). This characterization is supported by the fact that the power law function widely used for crystal and bubble size analysis is not a statistical distribution function, but rather represents an approximation of the upper regions (larger bubbles/crystals) of the logistic distribution, whose sizes are much larger than the mode. The coefficients for each of the four logarithmic functions can be derived by 1) best fit exceedance function of the logarithmic distribution, and 2) best fit of the linear transformation of the distribution probability density. A close match of the coefficients derived by the above two methods can be used as an indicator of correct function fitting (choice of initial values). Function fitting by exceedance curves leads to the most accurate statistical results, but has certain strict limitations, including 1) a requirement to rescale the base distribution function; 2) a higher failure rate for function fitting than that for distribution density; 3) uncertainty in observational data error estimates; and 4) unsuitability for visual interpretation. The most productive approach to visualization and interpretation of size distributions is through linear transformation of logarithmic distributions on the basis of probability densities. This also makes it possible to 1) clearly discern bimodal distributions; 2) assess the range of observed objects relative to the full range of the indicated distribution; 3) determine number densities for each mode directly; and 4) integrate to obtain total volume fraction for comparison with available observations. The latter could, in some cases, provide more accurate results than many measurement methods. Unambiguous definition of Bubble Number Density (BND) must be based on the number of bubbles per melt volume (not number of bubbles per bulk volume), so that like is done with crystals, it can be directly used as an indicator of basic vesiculation processes such that: a) nucleation leads to increase of BND, b) diffusive or decompressive bubble growth keeps BND constant, and c) coalescence decreases BND.
COMPLEX SYSTEMS ANALYSIS OF THE RISKS OF BLACKOUTS IN POWER TRANSMISSION SYSTEMS I. Dobson D. E. Newman B to fall off exponentially (as, for example, in a Weibull distribution). However, analyses of the NERC data has a profound effect on risk analysis for larger blackouts and the main purpose of this paper
Statistical modeling of tornado intensity distributions
NASA Astrophysics Data System (ADS)
Dotzek, Nikolai; Grieser, Jürgen; Brooks, Harold E.
We address the issue to determine an appropriate general functional shape of observed tornado intensity distributions. Recently, it was suggested that in the limit of long and large tornado records, exponential distributions over all positive Fujita or TORRO scale classes would result. Yet, our analysis shows that even for large databases observations contradict the validity of exponential distributions for weak (F0) and violent (F5) tornadoes. We show that observed tornado intensities can be much better described by Weibull distributions, for which an exponential remains a special case. Weibull fits in either v or F scale reproduce the observations significantly better than exponentials. In addition, we suggest to apply the original definition of negative intensity scales down to F-2 and T-4 (corresponding to v=0 m s -1) at least for climatological analyses. Weibull distributions allow for an improved risk assessment of violent tornadoes up to F6, and better estimates of total tornado occurrence, degree of underreporting and existence of subcritical tornadic circulations below damaging intensity. Therefore, our results are relevant for climatologists and risk assessment managers alike.
Distributed X-Ray Data and Distributed Analysis Tools
NASA Astrophysics Data System (ADS)
Plummer, D.; Schachter, J.; Elvis, M.; Garcia, M.; Conroy, M.
X-ray data and analysis packages can now be distributed directly to the desks of the user community using CDROMs and portable, familiar analysis packages (like IRAF/PROS). The Einstein IPC Slew Survey is an example of a complete X-ray data set distributed via CDROMs and is the first to use the new FITS standard for photon event lists (BINTABLE). Users can analyze the Slew data directly off the CDROM using PROS. As an example, we present a recipe for producing a radial profile of the Cygnus Loop using PROS and the Slew Survey CDROM data. CDROMs of the complete Einstein IPC and HRI archive data sets will soon be distributed in BINTABLE format allowing similar analysis with those data.
A novel approach for distribution fault analysis
Chow, Moyuen (North Carolina State Univ., Raleigh, NC (United States). Dept. of Electrical and Computer Engineering); Taylor, L.S. (Duke Power Co., Charlotte, NC (United States). Power Delivery Engineering Service)
1993-10-01
This paper proposes to use four different measures: actual values, normalized values, relative values, and likelihood values for power systems' distribution faults analysis. This paper also discusses the general and local properties of distribution faults. The likelihood measure, based on the local region properties, provides important information for distribution fault cause identification when the fault cause is not known. Tree faults on the Duke Power System are used in this paper for illustration purposes. The proposed measures, analysis and discussion in this paper can be easily generalized for different types of distribution faults in other utility companies.
Radial distribution function analysis of coir fibre
D. N. Mahato; B. K. Mathur; S. Bhattacherjee
1993-01-01
Radial distribution analysis of X-ray intensities diffracted by natural coir fibre subjected to various thermal and mercerization treatments has been carried out. Interatomic distances, mean square displacements and interatomic coupling constants have been obtained from the radial distribution curves. As coir fibre finds its various applications in its natural form, its study has been carried out without disturbing the configuration
SHIGEO SHIMIZU
2005-01-01
In almost all cases of the estimation of fatigue limit for structural materials and bearing steels, the practice of using S-N curves obtained by plotting the applied stress against the number of stress cycles has been continuing to date. It usually takes into account the probabilistic approach of dealing with the stress or force life for only median life. Therefore,
Weibull Statistics for Upper Ocean Currents with the Fokker-Planck Equation
NASA Astrophysics Data System (ADS)
Chu, P. C.
2012-12-01
Upper oceans typically exhibit of a surface mixed layer with a thickness of a few to several hundred meters. This mixed layer is a key component in studies of climate, biological productivity and marine pollution. It is the link between the atmosphere and the deep ocean and directly affects the air-sea exchange of heat, momentum and gases. Vertically averaged horizontal currents across the mixed layer are driven by the residual between the Ekman transport and surface wind stress, and damped by the Rayleigh friction. A set of stochastic differential equations are derived for the two components of the current vector (u, v). The joint probability distribution function of (u, v) satisfies the Fokker-Planck equation (Chu, 2008, 2009), with the Weibull distribution as the solution for the current speed. To prove it, the PDF of the upper (0-50 m) tropical Pacific current speeds (w) was calculated from hourly ADCP data (1990-2007) at six stations for the Tropical Atmosphere Ocean project. In fact, it satisfies the two-parameter Weibull distribution reasonably well with different characteristics between El Nino and La Nina events: In the western Pacific, the PDF of w has a larger peakedness during the La Nina events than during the El Nino events; and vice versa in the eastern Pacific. However, the PDF of w for the lower layer (100-200 m) does not fit the Weibull distribution so well as the upper layer. This is due to the different stochastic differential equations between upper and lower layers in the tropical Pacific. For the upper layer, the stochastic differential equations, established on the base of the Ekman dynamics, have analytical solution, i.e., the Rayleigh distribution (simplest form of the Weibull distribution), for constant eddy viscosity K. Knowledge on PDF of w during the El Nino and La Nina events will improve the ensemble horizontal flux calculation, which contributes to the climate studies. Besides, the Weibull distribution is also identified from the near-real time ocean surface currents derived from satellite altimeter (JASON-1, GFO, ENVISAT) and scatterometer (QSCAT) data on 1o 1o resolution for world oceans (60o S to 60o N) as "Ocean Surface Current Analyses - Real Time (OSCAR)". Such a PDF has little seasonal and interannual variations. Knowledge on PDF of w will improve the ensemble horizontal flux calculation, which contributes to the climate studies. References Chu, P. C., 2008: Probability distribution function of the upper equatorial Pacific current speeds. Geophysical Research Letters, 35,doi:10.1029/2008GL033669 Chu, P. C., 2009: Statistical Characteristics of the Global Surface Current Speeds Obtained from Satellite Altimeter and Scatterometer Data. IEEE Journal of Selected Topics in Earth Observations and Remote Sensing,2(1),27-32.
Application of Weibull Criterion to failure prediction in compsites
Cain, W. D.; Knight, Jr., C. E.
1981-04-20
Fiber-reinforced composite materials are being widely used in engineered structures. This report examines how the general form of the Weibull Criterion, including the evaluation of the parameters and the scaling of the parameter values, can be used for the prediction of component failure.
NSDL National Science Digital Library
Siegrist, Kyle
This online, interactive lesson on special distributions provides examples, exercises, and applets covering normal, gamma, chi-square, student t, F, bivariate, normal, multivariate normal, beta, weibull, zeta, pareto, logistic, lognormal, and extreme value distributions. Overall, this lesson covers a plethora of topics, and for this reason, is a valuable resource.
Extreme Value Distributions Isabel Fraga Alves
Alves, Maria Isabel Fraga
engineer and scientist well-known for his work on strength of materials and fatigue analysis (Weibull, 1939(-x)}, x R; (ii) Fr´echet (type II): (x) = 0, x 0; exp{-x-}, x > 0, > 0; (iii) Weibull (type III): (x project. 1 #12;(iii) Weibull : E[X] = -(1 + 1/); V ar[X] = (1 + 2/) - 2(1 + 1/); Mode = -(1 - 1
Telomere Length Distribution and Southern Blot Analysis
Konrad Oexle
1998-01-01
Southern blot analysis of terminal restriction fragments (TRFs) is the standard method for quantitative examination of telomere length distributions. Since TRFs contain a subtelomeric component, central parameters of the TRF distributionn(L) such as the arithmetic mean (M) or the median (Me) cannot be derived directly from Southern blot data, i.e. from the optical density distributionOD(L). Several estimates have been applied
Shuttle Electrical Power Analysis Program (SEPAP) distribution circuit analysis report
NASA Technical Reports Server (NTRS)
Torina, E. M.
1975-01-01
An analysis and evaluation was made of the operating parameters of the shuttle electrical power distribution circuit under load conditions encountered during a normal Sortie 2 Mission with emphasis on main periods of liftoff and landing.
Fitting LogF Models Robustly, with an Application to the Analysis of Extreme Values
Dupuis, Debbie
Fitting LogF Models Robustly, with an Application to the Analysis of Extreme Values by D.J. Dupuis the lognormal, extremevalue, Weibull, loglogistic, reciprocal Weibull, and generalized gamma distri
Towards Distributed Memory Parallel Program Analysis
Quinlan, D; Barany, G; Panas, T
2008-06-17
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.
Testing traffic congestion by distributed protocol analysis
Vlatko Lipovac; Vedran Batos; Boris Nemsic
2010-01-01
In this paper, we propose the concept and the means for practical testing of TCP congestion window. With this respect, we present the architecture of the hardware and expert-system-based distributed protocol analysis that we used for practical data acquisition and testing, which we conducted on a major network with live traffic (Electronic Financial Transactions data transfer), as well as the
Distributed leadership as a unit of analysis
Peter Gronn
2002-01-01
This article proposes a new unit of analysis in the study of leadership. As an alternative to the current focus, which is primarily on the deeds of individual leaders, the article proposes distributed leadership. The article shows how conventional constructs of leadership have difficulty accommodating changes in the division of labor in the workplace, especially, new patterns of interdependence and
Parton distributions: a new global analysis
A. D. Martin; R. G. Roberts; W. J. Stirling; R. S. Thorne
1998-01-01
We present a new analysis of parton distributions of the proton. This incorporates a wide range of new data, an improved treatment of heavy flavours and a re-examination of prompt photon production. The new set (MRST) shows systematic differences from previous sets of partons which can be identified with particular features of the new data and with improvements in the
Effects of cyclic stress distribution models on fatigue life predictions
NASA Astrophysics Data System (ADS)
Sutherland, H. J.; Veers, P. S.
1994-10-01
The fatigue analysis of a wind turbine component typically uses representative samples of cyclic loads to determine lifetime loads. In this paper, several techniques currently in use are compared to one another based on fatigue life analyses. The generalized Weibull fitting technique is used to remove the artificial truncation of large-amplitude cycles that is inherent in relatively short data sets. Using data from the Sandia/DOE 34-m Test Bed, the generalized Weibull file technique is shown to be excellent for matching the body of the distribution of cyclic loads and for extrapolating the tail of the distribution. However, the data also illustrate that the fitting technique is not a substitute for an adequate data base.
Modeling particle distributions for stray light analysis
NASA Astrophysics Data System (ADS)
Fleming, John; Matheson, Bruce; Dittman, Michael G.; Grochocki, Frank; Firth, Brenda
2006-08-01
There has been a general awareness for several years that the IEST-STD-CC1246 standard particle distribution with a slope of -0.926 does not reasonably represent the contamination on optics that have not been recently cleaned. As a result, the CL (Cleanliness Level) nomenclature actually counters effective communication and modeling of particulate contamination scatter. An analysis method and communication standard centered on Percent Areal Coverage (PAC) and particle distribution slope is presented that improves the ability of Contamination Engineering and Stray Light Engineering to tackle ever more difficult instrument stray light requirements in the most cost-effective manner. Modeling the expected particle distributions for multiple contamination species improves accuracy and reduces costly overdesign.
Petry, M.D.; Mah, T.I. [UES Inc., Dayton, OH (United States); Kerans, R.J. [Materials Directorate, Wright-Patterson AFB, OH (United States). Wright Lab.
1997-10-01
Strengths and Weibull moduli for alumina/yttrium aluminum garnet eutectic (AYE) filaments and for Si-C-O (Nicalon) filaments were calculated using measured and average filament diameters. The strengths agreed closely. Thus an average filament diameter could be used instead of the measured filament diameter in calculating strengths. The Weibull modulus obtained from an average filament diameter approximates the Weibull modulus obtained using the measured filament diameter.
Wigner distribution analysis of acoustic well logs
G. F. Boudreaux-Bartels; P. Wiseman
1987-01-01
We use the Wigner distribution(WD) mixed time-frequency representation(TFR) to design two heuristic algorithms that can be used to analyze and separate the compressional(P), shear(S), Pseudo-Rayleigh (PR), and Stoneley(ST) wave components of the multi-component time-varying borehole seismic signals recorded in well logging velocity surveys. The first algorithm uses auto WD analysis, modification, and synthesis techniques to successively isolate each of the
Modeling particle distributions for stray light analysis
John Fleming; Bruce Matheson; Michael G. Dittman; Frank Grochocki; Brenda Firth
2006-01-01
There has been a general awareness for several years that the IEST-STD-CC1246 standard particle distribution with a slope of -0.926 does not reasonably represent the contamination on optics that have not been recently cleaned. As a result, the CL (Cleanliness Level) nomenclature actually counters effective communication and modeling of particulate contamination scatter. An analysis method and communication standard centered on
Parton distributions: a new global analysis
A. D. Martin; R. G. Roberts; W. J. Stirling; R. S. Thorne
1998-01-01
We present a new analysis of parton distributions of the proton. This\\u000aincorporates a wide range of new data, an improved treatment of heavy flavours\\u000aand a re-examination of prompt photon production. The new set (MRST) shows\\u000asystematic differences from previous sets of partons which can be identified\\u000awith particular features of the new data and with improvements in the
Parton distributions: a new global analysis
A. D. Martin; R. G. Roberts; W. J. Stirling; R. S. Thorne
1998-01-01
. We present a new analysis of parton distributions of the proton. This incorporates a wide range of new data, an improved\\u000a treatment of heavy flavours and a re-examination of prompt photon production. The new set (MRST) shows systematic differences\\u000a from previous sets of partons which can be identified with particular features of the new data and with improvements in
Analysis of fire size distribution in Portugal
NASA Astrophysics Data System (ADS)
Pereira, Mário; Calado, Teresa; Camara, Carlos; Trigo, Ricardo
2010-05-01
In this work we have applied statistical methods to characterize the variability of forest fires in Portugal, and additionally assess the role of meteorological conditions on fire size. Appropriate distribution functions were tested to fit the high positively skewed fire size samples. Maximum Likelihood Estimates (MLE) of distribution parameters were derived from a 28 year database of fire occurrences and the goodness of fit was assessed by standard Kolmogorov-Smirnov, Crámer von-Mises and Anderson-Darling statistical tests as well as by qq-plots. Weather conditions, namely air temperature, precipitation and wind have significant influence on vegetation physiological state and the impact on fire size was studied by using these variables as meteorological covariates of the above derived statistical distributions. The following datasets covering the 1980-2007 period were used: 1) the Portuguese Rural fire database, provided by the Forest National Authority and 2) daily values of meteorological variables, as well as atmospheric circulation indices as obtained from weather typing analysis and fire risk indices. The methodology was applied considering all fire records in the database and fires registered in particular periods and/or locations. Results reveal the usefulness of parametric models to characterize the observed fire size distribution and to assess the role of meteorological conditions on fire size distribution.
Probability distributions for offshore wind speeds Eugene C. Morgan a,*, Matthew Lackner b
Vogel, Richard M.
Wind turbine energy output Weibull distribution Extreme wind a b s t r a c t In planning offshore windProbability distributions for offshore wind speeds Eugene C. Morgan a,*, Matthew Lackner b parameters. It is common practice to model short-term wind speeds with the Weibull distribution. Using 10-min
Distributed processing for multiresolution dynamic scene analysis
Tan, C.L.
1986-01-01
High computational cost has long been a problem in computer vision. A model to alleviate this problem in motion analysis is presented. The model is a hybrid of three techniques, namely, hierarchical structures, parallelism, and selective analysis control. A pipelined pyramid image structure is constructed in the model by continually converging incoming images into successively coarser resolutions. The model also contains a set of processes that work concurrently and asynchronously on subimages at different levels of this pyramid structure. These processes initially watch for interesting features in the coarsest resolution rendition of the scene. Processes working on promising areas individually but cooperatively proceed to progressively finer-resolution levels according to a selective-analysis control strategy. The control mechanism is afforded through a blackboard structure, which also permits a unified-scene interpretation. The model was implemented in a simulated distributed system. Implementation results with different image sequences including ambiguous and conclusion scenes are presented.
Offshore wind resource assessment with Standard Wind Analysis Tool (SWAT): A Rhode Island case study
NASA Astrophysics Data System (ADS)
Crosby, Alexander Robert
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.
Distribution System Analysis Tools for Studying High Penetration of PV
Distribution System Analysis Tools for Studying High Penetration of PV with Grid Support Features Electric Energy System #12;#12;Distribution System Analysis Tools for Studying High Penetration of PV project titled "Distribution System Analysis Tools for Studying High Penetration of PV with Grid Support
Modeling and Analysis of Power Distribution Networks for Gigabit Applications
Swaminathan, Madhavan
Modeling and Analysis of Power Distribution Networks for Gigabit Applications Jinwoo Choi, Student and coupling. To minimize such noise behavior, prelayout analysis and postlayout verification of the power and analysis of the power distribution network. The power distribution network supplies power to core logic
Distribution System Analysis to support the Smart Grid
R. C. Dugan; R. F. Arritt; T. E. McDermott; S. M. Brahma; K. Schneider
2010-01-01
The “Smart Grid” refers to various efforts to modernize the power grid through the application of intelligent devices. This paper describes current thinking by members of the Distribution System Analysis Subcommittee (DSA SC) on how distribution system analysis might evolve to support the Smart Grid. Various issues related to Smart Grid and distribution system analysis are identified. The essential characteristics
Analysis and control of distributed cooperative systems.
Feddema, John Todd; Parker, Eric Paul; Wagner, John S.; Schoenwald, David Alan
2004-09-01
As part of DARPA Information Processing Technology Office (IPTO) Software for Distributed Robotics (SDR) Program, Sandia National Laboratories has developed analysis and control software for coordinating tens to thousands of autonomous cooperative robotic agents (primarily unmanned ground vehicles) performing military operations such as reconnaissance, surveillance and target acquisition; countermine and explosive ordnance disposal; force protection and physical security; and logistics support. Due to the nature of these applications, the control techniques must be distributed, and they must not rely on high bandwidth communication between agents. At the same time, a single soldier must easily direct these large-scale systems. Finally, the control techniques must be provably convergent so as not to cause undo harm to civilians. In this project, provably convergent, moderate communication bandwidth, distributed control algorithms have been developed that can be regulated by a single soldier. We have simulated in great detail the control of low numbers of vehicles (up to 20) navigating throughout a building, and we have simulated in lesser detail the control of larger numbers of vehicles (up to 1000) trying to locate several targets in a large outdoor facility. Finally, we have experimentally validated the resulting control algorithms on smaller numbers of autonomous vehicles.
Test Population Selection from Weibull-Based, Monte Carlo Simulations of Fatigue Life
NASA Technical Reports Server (NTRS)
Vlcek, Brian L.; Zaretsky, Erwin V.; Hendricks, Robert C.
2012-01-01
Fatigue life is probabilistic and not deterministic. Experimentally establishing the fatigue life of materials, components, and systems is both time consuming and costly. As a result, conclusions regarding fatigue life are often inferred from a statistically insufficient number of physical tests. A proposed methodology for comparing life results as a function of variability due to Weibull parameters, variability between successive trials, and variability due to size of the experimental population is presented. Using Monte Carlo simulation of randomly selected lives from a large Weibull distribution, the variation in the L10 fatigue life of aluminum alloy AL6061 rotating rod fatigue tests was determined as a function of population size. These results were compared to the L10 fatigue lives of small (10 each) populations from AL2024, AL7075 and AL6061. For aluminum alloy AL6061, a simple algebraic relationship was established for the upper and lower L10 fatigue life limits as a function of the number of specimens failed. For most engineering applications where less than 30 percent variability can be tolerated in the maximum and minimum values, at least 30 to 35 test samples are necessary. The variability of test results based on small sample sizes can be greater than actual differences, if any, that exists between materials and can result in erroneous conclusions. The fatigue life of AL2024 is statistically longer than AL6061 and AL7075. However, there is no statistical difference between the fatigue lives of AL6061 and AL7075 even though AL7075 had a fatigue life 30 percent greater than AL6061.
Test Population Selection from Weibull-Based, Monte Carlo Simulations of Fatigue Life
NASA Technical Reports Server (NTRS)
Vlcek, Brian L.; Zaretsky, Erwin V.; Hendricks, Robert C.
2008-01-01
Fatigue life is probabilistic and not deterministic. Experimentally establishing the fatigue life of materials, components, and systems is both time consuming and costly. As a result, conclusions regarding fatigue life are often inferred from a statistically insufficient number of physical tests. A proposed methodology for comparing life results as a function of variability due to Weibull parameters, variability between successive trials, and variability due to size of the experimental population is presented. Using Monte Carlo simulation of randomly selected lives from a large Weibull distribution, the variation in the L10 fatigue life of aluminum alloy AL6061 rotating rod fatigue tests was determined as a function of population size. These results were compared to the L10 fatigue lives of small (10 each) populations from AL2024, AL7075 and AL6061. For aluminum alloy AL6061, a simple algebraic relationship was established for the upper and lower L10 fatigue life limits as a function of the number of specimens failed. For most engineering applications where less than 30 percent variability can be tolerated in the maximum and minimum values, at least 30 to 35 test samples are necessary. The variability of test results based on small sample sizes can be greater than actual differences, if any, that exists between materials and can result in erroneous conclusions. The fatigue life of AL2024 is statistically longer than AL6061 and AL7075. However, there is no statistical difference between the fatigue lives of AL6061 and AL7075 even though AL7075 had a fatigue life 30 percent greater than AL6061.
Assessing a Tornado Climatology from Global Tornado Intensity Distributions
Bernold Feuerstein; Nikolai Dotzek; Jürgen Grieser
2005-01-01
Recent work demonstrated that the shape of tornado intensity distributions from various regions worldwide is well described by Weibull functions. This statistical modeling revealed a strong correlation between the fit parameters c for shape and b for scale regardless of the data source. In the present work it is shown that the quality of the Weibull fits is optimized if
Rectangular shape distributed piezoelectric actuator: analytical analysis
NASA Astrophysics Data System (ADS)
Sun, Bohua; Qiu, Yan
2004-04-01
This paper is focused on the development of distributed piezoelectric actuators (DPAs) with rectangular shapes by using PZT materials. Analytical models of rectangular shape DPAs have been constructed in order to analyse and test the performance of DPA products. Firstly, based on the theory of electromagnetics, DPAs have been considered as a type of capacitor. The charge distributed density on the interdigitated electrodes (IDEs), which has been applied in the actuators, and the capacitance of the DPAs have been calculated. The accurate distribution and intensity of electrical field in DPA element have also been calculated completely. Secondly, based on the piezoelectric constitutive relations and the compound plates theory, models for mechanical strain and stress fields of DPAs have been developed, and the performances of rectangular shape DPAs have been discussed. Finally, on the basis of the models that have been developed in this paper, an improved design of a rectangular shape DPA has been discussed and summed up. Due to the minimum hypotheses that have been used during the processes of calculation, the characteristics of this paper are that the accurate distribution and intensity of electrical fields in DPAs have been concluded. The proposed accurate calculations have not been seen in the literature, and can be used in DPA design and manufacture processes in order to improve mechanical performance and reduce the cost of DPA products in further applications. In this paper, all the processes of analysis and calculation have been done by MATLAB and MathCAD. The FEM results used for comparison were obtained using the ABAQUS program.
Ceramics Analysis and Reliability Evaluation of Structures (CARES). Users and programmers manual
NASA Technical Reports Server (NTRS)
Nemeth, Noel N.; Manderscheid, Jane M.; Gyekenyesi, John P.
1990-01-01
This manual describes how to use the Ceramics Analysis and Reliability Evaluation of Structures (CARES) computer program. The primary function of the code is to calculate the fast fracture reliability or failure probability of macroscopically isotropic ceramic components. These components may be subjected to complex thermomechanical loadings, such as those found in heat engine applications. The program uses results from MSC/NASTRAN or ANSYS finite element analysis programs to evaluate component reliability due to inherent surface and/or volume type flaws. CARES utilizes the Batdorf model and the two-parameter Weibull cumulative distribution function to describe the effect of multiaxial stress states on material strength. The principle of independent action (PIA) and the Weibull normal stress averaging models are also included. Weibull material strength parameters, the Batdorf crack density coefficient, and other related statistical quantities are estimated from four-point bend bar or unifrom uniaxial tensile specimen fracture strength data. Parameter estimation can be performed for single or multiple failure modes by using the least-square analysis or the maximum likelihood method. Kolmogorov-Smirnov and Anderson-Darling goodness-of-fit tests, ninety percent confidence intervals on the Weibull parameters, and Kanofsky-Srinivasan ninety percent confidence band values are also provided. The probabilistic fast-fracture theories used in CARES, along with the input and output for CARES, are described. Example problems to demonstrate various feature of the program are also included. This manual describes the MSC/NASTRAN version of the CARES program.
Design and Analysis of a Distributed Regenerative Frequency Divider Using a Distributed Mixer
Heydari, Payam
Design and Analysis of a Distributed Regenerative Frequency Divider Using a Distributed Mixer Amin-2625 ABSTRACT In this paper we present the design and analysis of a distributed regenerative frequency divider in 1939, a regenerative frequency divider is essentially a non-linear feedback circuit consisting
Shadow Imaging for Charge Distribution Analysis
NASA Astrophysics Data System (ADS)
Zhu, Yimei; Wu, Lijun
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.
Electron density distribution analysis for nitroguanidine
Ritchie, J.P.; Cromer, D.T.; Stewart, R.F.; Wasserman, H.J.; Ryan, R.R.
1985-01-01
The electron density distribution of nitroguanidine was analyzed with both experimental and theoretical techniques to determine how well these methods would work for an explosive molecule. Explosives present special problems with these methods because many atoms are usually involved, which can cause the calculations to become intractable, and because the molecules have many polar bonds. We found that, although the polar character of the space group made the experimental analysis difficult, the two techniques yielded results very much in harmony. Specifically, electrostatic potentials, which play a large role in determining crystal geometry, were in very good agreement. A discrepancy, however, was observed between the theoretically optimized geometry and the observed geometry. This discrepancy appears to be the result of crystal packing forces which are not present in the theoretical calculations. We also observed some similarities between the hydrogen-bond network in NQ and that in TATB. 14 refs., 9 figs., 2 tabs.
Holistic schedulability analysis for distributed hard real-time systems
Ken Tindell; John Clark
1994-01-01
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
Likelihood analysis of earthquake focal mechanism distributions
NASA Astrophysics Data System (ADS)
Kagan, Yan Y.; Jackson, David D.
2015-06-01
In our paper published earlier we discussed forecasts of earthquake focal mechanism and ways to test the forecast efficiency. Several verification methods were proposed, but they were based on ad hoc, empirical assumptions, thus their performance is questionable. We apply a conventional likelihood method to measure the skill of earthquake focal mechanism orientation forecasts. The advantage of such an approach is that earthquake rate prediction can be adequately combined with focal mechanism forecast, if both are based on the likelihood scores, resulting in a general forecast optimization. We measure the difference between two double-couple sources as the minimum rotation angle that transforms one into the other. We measure the uncertainty of a focal mechanism forecast (the variability), and the difference between observed and forecasted orientations (the prediction error), in terms of these minimum rotation angles. To calculate the likelihood score we need to compare actual forecasts or occurrences of predicted events with the null hypothesis that the mechanism's 3-D orientation is random (or equally probable). For 3-D rotation the random rotation angle distribution is not uniform. To better understand the resulting complexities, we calculate the information (likelihood) score for two theoretical rotational distributions (Cauchy and von Mises-Fisher), which are used to approximate earthquake source orientation pattern. We then calculate the likelihood score for earthquake source forecasts and for their validation by future seismicity data. Several issues need to be explored when analyzing observational results: their dependence on forecast and data resolution, internal dependence of scores on forecasted angle and random variability of likelihood scores. Here, we propose a simple tentative solution but extensive theoretical and statistical analysis is needed.
Distribution system power flow analysis; A rigid approach
T.-H. Chen; M.-S. Chen; K.-J. Hwang; P. Kotas; E. A. Chebli
1991-01-01
This paper introduces a rigid approach to three-phase distribution power flow analysis for large-scale distribution systems. This approach is oriented toward applications in distribution system operational analysis rather than planning analysis. This difference should be properly emphasized, otherwise, the misuse of the planning-type method to analyze the operational behavior of the system will distort the explanation of the calculated results
Weibull Data Analysis with Few or no Failures
Ming-Wei Lu; Cheng Julius Wang
Laboratory testing is a critical step in the development of vehicle components or systems. It allows the design engineer to\\u000a evaluate the design early in the reliability development phase. A good lab test will shorten the product development cycles\\u000a and minimizes cost and part failures at the PG or field testing before the vehicle volume production. Appropriate testing\\u000a is available
Modeling and analysis of distribution reliability indices
Nagaraj Balijepalli; Subrahmanyam S. Venkata; Richard D. Christie
2004-01-01
Assessment of customer power supply reliability is an important part of distribution system operation and planning. Monte Carlo simulations can be used to find the statistical distribution of the reliability indices, along with their mean and standard deviation. The standard deviation of the reliability indices provides distribution engineers with information on the expected range of the annual values. However, the
A power series beta Weibull regression model for predicting breast carcinoma.
Ortega, Edwin M M; Cordeiro, Gauss M; Campelo, Ana K; Kattan, Michael W; Cancho, Vicente G
2015-04-15
The postmastectomy survival rates are often based on previous outcomes of large numbers of women who had a disease, but they do not accurately predict what will happen in any particular patient's case. Pathologic explanatory variables such as disease multifocality, tumor size, tumor grade, lymphovascular invasion, and enhanced lymph node staining are prognostically significant to predict these survival rates. We propose a new cure rate survival regression model for predicting breast carcinoma survival in women who underwent mastectomy. We assume that the unknown number of competing causes that can influence the survival time is given by a power series distribution and that the time of the tumor cells left active after the mastectomy for metastasizing follows the beta Weibull distribution. The new compounding regression model includes as special cases several well-known cure rate models discussed in the literature. The model parameters are estimated by maximum likelihood. Further, for different parameter settings, sample sizes, and censoring percentages, some simulations are performed. We derive the appropriate matrices for assessing local influences on the parameter estimates under different perturbation schemes and present some ways to assess local influences. The potentiality of the new regression model to predict accurately breast carcinoma mortality is illustrated by means of real data. PMID:25620602
Survival Analysis of Patients with End Stage Renal Disease
NASA Astrophysics Data System (ADS)
Urrutia, J. D.; Gayo, W. S.; Bautista, L. A.; Baccay, E. B.
2015-06-01
This paper provides a survival analysis of End Stage Renal Disease (ESRD) under Kaplan-Meier Estimates and Weibull Distribution. The data were obtained from the records of V. L. MakabaliMemorial Hospital with respect to time t (patient's age), covariates such as developed secondary disease (Pulmonary Congestion and Cardiovascular Disease), gender, and the event of interest: the death of ESRD patients. Survival and hazard rates were estimated using NCSS for Weibull Distribution and SPSS for Kaplan-Meier Estimates. These lead to the same conclusion that hazard rate increases and survival rate decreases of ESRD patient diagnosed with Pulmonary Congestion, Cardiovascular Disease and both diseases with respect to time. It also shows that female patients have a greater risk of death compared to males. The probability risk was given the equation R = 1 — e-H(t) where e-H(t) is the survival function, H(t) the cumulative hazard function which was created using Cox-Regression.
L. P. Bayvel
1985-01-01
A method is described which enables one to find from an experimentally determined number or mass drop size distribution the 'best' fit to standard distribution functions such as Rosin-Rammler, log-normal, root-normal, Nukiyama-Tanasawa, upper limit, as well as various means and parameters of these distributions, together with their variances. An example analysis of the drop size distribution of a spray is
Freight distribution systems with cross-docking: a multidisciplinary analysis
-Feliu and Morana, 2010). · Logistic systems for urban freight distribution have also evolved into multi1 Freight distribution systems with cross-docking: a multidisciplinary analysis Jesus Gonzalez-echelon distribution is one of the most common strategies adopted by the transport companies in an aim of cost
Real-Time Analysis of Round-based Distributed Algorithms
Real-Time Analysis of Round-based Distributed Algorithms Alexander KÂ¨oÃ?ler, Heinrich Moser, Ulrich,moser,s}@ecs.tuwien.ac.at I. DISTRIBUTED COMPUTING VS. REAL-TIME SYSTEMS RESEARCH Designing sound fault-tolerant distributed real-time systems requires a scientific basis, which allows to cope with three very different
On-The-Fly Analysis of Distributed Computations
Eddy Fromentin; Claude Jard; Guy-vincent Jourdan; Michel Raynal
1995-01-01
At some abstraction level a distributed computation can be modeled as a partial order on a set of observable events. This paper presents an analysis technique which can be superimposed on distributed computations to analyze the structure of control flows terminating at observable events. A general algorithm working on the longest control flows of distributed computations is introduced. Moreover it
A Requirement Analysis for High Performance Distributed Computing over LAN's
Parashar, Manish
A Requirement Analysis for High Performance Distributed Computing over LAN's Manish Parashar them to be used as platforms for high performance distributed comput- ing. The blocked L U enable a network of workstations to deliver high performance distributed computing. 1 Introduction
Stochastic Analysis of Wind Energy for Wind Pump Irrigation in Coastal Andhra Pradesh, India
NASA Astrophysics Data System (ADS)
Raju, M. M.; Kumar, A.; Bisht, D.; Rao, D. B.
2014-09-01
The rapid escalation in the prices of oil and gas as well as increasing demand for energy has attracted the attention of scientists and researchers to explore the possibility of generating and utilizing the alternative and renewable sources of wind energy in the long coastal belt of India with considerable wind energy resources. A detailed analysis of wind potential is a prerequisite to harvest the wind energy resources efficiently. Keeping this in view, the present study was undertaken to analyze the wind energy potential to assess feasibility of the wind-pump operated irrigation system in the coastal region of Andhra Pradesh, India, where high ground water table conditions are available. The stochastic analysis of wind speed data were tested to fit a probability distribution, which describes the wind energy potential in the region. The normal and Weibull probability distributions were tested; and on the basis of Chi square test, the Weibull distribution gave better results. Hence, it was concluded that the Weibull probability distribution may be used to stochastically describe the annual wind speed data of coastal Andhra Pradesh with better accuracy. The size as well as the complete irrigation system with mass curve analysis was determined to satisfy various daily irrigation demands at different risk levels.
Shark: Fast Data Analysis Using Coarse-grained Distributed Memory
California at Irvine, University of
Shark: Fast Data Analysis Using Coarse-grained Distributed Memory Cliff Engle, Antonio Lupher {cengle, alupher, rxin, matei, franklin, shenker, istoica}@cs.berkeley.edu ABSTRACT Shark is a research data analysis system built on a novel coarse-grained distributed shared-memory abstraction. Shark
Performance Analysis of Distributed Information Retrieval Architectures
Brendon Cahoon; Kathryn McKinley
Large document collections are increasingly available over the network. In order for users to access these collections, information retrieval systems must provide coordinated, concurrent, and distributed access. Since even unified information retrieval (IR) systems place heavy demands on system resources, it is unclear how performance will be affected as user demand increases and the distributed IR systems grow in size.
Bayesian Analysis of a Generalized Poisson Distribution
M. M. Shoukri; P. C. Consul
1989-01-01
A generalized form of the Poisson Distribution with two parameters will be estimated by the Bayesian technique. When one of the parameters is known, several important parametric functions will be estimated and a numerical comparison with estimates obtained by the methods of maximum likelihood and unbiased minimum variance will be drawn. The simplicity of the posterior distribution of the unknown
Fracture mechanics concepts in reliability analysis of monolithic ceramics
NASA Technical Reports Server (NTRS)
Manderscheid, Jane M.; Gyekenyesi, John P.
1987-01-01
Basic design concepts for high-performance, monolithic ceramic structural components are addressed. The design of brittle ceramics differs from that of ductile metals because of the inability of ceramic materials to redistribute high local stresses caused by inherent flaws. Random flaw size and orientation requires that a probabilistic analysis be performed in order to determine component reliability. The current trend in probabilistic analysis is to combine linear elastic fracture mechanics concepts with the two parameter Weibull distribution function to predict component reliability under multiaxial stress states. Nondestructive evaluation supports this analytical effort by supplying data during verification testing. It can also help to determine statistical parameters which describe the material strength variation, in particular the material threshold strength (the third Weibull parameter), which in the past was often taken as zero for simplicity.
NONNORMAL REGRESSION. I. SKEW DISTRIBUTIONS
M. Qamarul Islam; Moti L. Tiku; F. Yildirim
2001-01-01
In a linear regression model of the type y= ? X+e, it is often assumed that the random error eis normally distributed. In numerous situations, e.g., when ymeasures life times or reaction times, etypically has a skew distribution. We consider two important families of skew distributions, (a) Weibull with support IR: (0, ?) on the real line, and (b) generalised
Analysis of Temperature Distributions in Nighttime Inversions
NASA Astrophysics Data System (ADS)
Telyak, Oksana; Krasouski, Aliaksandr; Svetashev, Alexander; Turishev, Leonid; Barodka, Siarhei
2015-04-01
Adequate prediction of temperature inversion in the atmospheric boundary layer is one of prerequisites for successful forecasting of meteorological parameters and severe weather events. Examples include surface air temperature and precipitation forecasting as well as prediction of fog, frosts and smog with hazardous levels of atmospheric pollution. At the same time, reliable forecasting of temperature inversions remains an unsolved problem. For prediction of nighttime inversions over some specific territory, it is important to study characteristic features of local circulation cells formation and to properly take local factors into account to develop custom modeling techniques for operational use. The present study aims to investigate and analyze vertical temperature distributions in tropospheric inversions (isotherms) over the territory of Belarus. We study several specific cases of formation, evolution and decay of deep nighttime temperature inversions in Belarus by means of mesoscale numerical simulations with WRF model, considering basic mechanisms of isothermal and inverse temperature layers formation in the troposphere and impact of these layers on local circulation cells. Our primary goal is to assess the feasibility of advance prediction of inversions formation with WRF. Modeling results reveal that all cases under consideration have characteristic features of radiative inversions (e.g., their formation times, development phases, inversion intensities, etc). Regions of "blocking" layers formation are extensive and often spread over the entire territory of Belarus. Inversions decay starts from the lowermost (near surface) layer (altitudes of 5 to 50 m). In all cases, one can observe formation of temperature gradients that substantially differ from the basic inversion gradient, i.e. the layer splits into smaller layers, each having a different temperature stratification (isothermal, adiabatic, etc). As opposed to various empirical techniques as well as theoretical approaches based on discriminant analysis, mesoscale modeling with WRF provides fairly successful forecasts of formation times and regions for all types of temperature inversions up to 3 days in advance. Furthermore, we conclude that without proper adjustment for the presence of thin isothermal layers (adiabatic and/or inversion layers), temperature data can affect results of statistical climate studies. Provided there are regions where a long-term, constant inversion is present (e.g., Antarctica or regions with continental climate), these data can contribute an uncompensated systematic error of 2 to 10° C. We argue that this very fact may lead to inconsistencies in long-term temperature data interpretations (e.g., conclusions ranging from "global warming" to "global cooling" based on temperature observations for the same region and time period). Due to the importance of this problem from the scientific as well as practical point of view, our plans for further studies include analysis of autumn and wintertime inversions and convective inversions. At the same time, it seems promising to develop an algorithm of automatic recognition of temperature inversions based on a combination of WRF modeling results, surface and satellite observations.
Principal Component Analysis for Distributed Data Sets with Updating
Chan, Raymond
Principal Component Analysis for Distributed Data Sets with Updating Zheng-Jian Bai1, , Raymond H Effective clustering of large data sets is a major objective in data mining. Principal component analysis is effective for high-dimensional data analysis when the data sets are collo- cated. However, in present
TV Watcher: Distributed Media Analysis and Correlation
David Hilley; Ahmed El-Helw; Matthew Wolenetz; Irfan Essa; Phillip Hutto; Thad Starner; Umakishore Ramachandran
The explosion of available content in broadcast media has cre- ated a desperate need for applications and prerequisite system architectures to support automatic capture, filtration, categoriza- tion, correlation, and higher level inferencing of streaming data from distributed sources. We present TV Watcher, an archetyp- ical example of such an application. TV Watcher performs user- controlled correlation of live television feeds
Hierarchical analysis of power distribution networks
Min Zhao; Rajendran V. Panda; Sachin S. Sapatnekar; David T. Blaauw
2002-01-01
Careful design and verification of the power distribution network of a chip are of critical importance to ensure its reliable performance. With the increasing number of transistors on a chip, the size of the power network has grown so large as to make the verification task very challenging. The available computational power and memory resources impose limitations on the size
Hierarchical analysis of power distribution networks
Min Zhao; Rajendran V. Panda; Sachin S. Sapatnekar; Tim Edwards; Rajat Chaudhry; David Blaauw
2000-01-01
Careful design and verification of the power distribution network of a chip are of critical importance to ensure its reliable performance. With the increasing number of transistors on a chip, the size of the power network has grown so large as to make the verification task very challenging. The available computational power and memory resources impose limitations on the size
Newcombe, Pj; Raza Ali, H; Blows, Fm; Provenzano, E; Pharoah, Pd; Caldas, C; Richardson, S
2014-09-01
As data-rich medical datasets are becoming routinely collected, there is a growing demand for regression methodology that facilitates variable selection over a large number of predictors. Bayesian variable selection algorithms offer an attractive solution, whereby a sparsity inducing prior allows inclusion of sets of predictors simultaneously, leading to adjusted effect estimates and inference of which covariates are most important. We present a new implementation of Bayesian variable selection, based on a Reversible Jump MCMC algorithm, for survival analysis under the Weibull regression model. A realistic simulation study is presented comparing against an alternative LASSO-based variable selection strategy in datasets of up to 20,000 covariates. Across half the scenarios, our new method achieved identical sensitivity and specificity to the LASSO strategy, and a marginal improvement otherwise. Runtimes were comparable for both approaches, taking approximately a day for 20,000 covariates. Subsequently, we present a real data application in which 119 protein-based markers are explored for association with breast cancer survival in a case cohort of 2287 patients with oestrogen receptor-positive disease. Evidence was found for three independent prognostic tumour markers of survival, one of which is novel. Our new approach demonstrated the best specificity. PMID:25193065
Effect of covariate omission in Weibull accelerated failure time model: a caution.
Gosho, Masahiko; Maruo, Kazushi; Sato, Yasunori
2014-11-01
The accelerated failure time model is presented as an alternative to the proportional hazard model in the analysis of survival data. We investigate the effect of covariates omission in the case of applying a Weibull accelerated failure time model. In an uncensored setting, the asymptotic bias of the treatment effect is theoretically zero when important covariates are omitted; however, the asymptotic variance estimator of the treatment effect could be biased and then the size of the Wald test for the treatment effect is likely to exceed the nominal level. In some cases, the test size could be more than twice the nominal level. In a simulation study, in both censored and uncensored settings, Type I error for the test of the treatment effect was likely inflated when the prognostic covariates are omitted. This work remarks the careless use of the accelerated failure time model. We recommend the use of the robust sandwich variance estimator in order to avoid the inflation of the Type I error in the accelerated failure time model, although the robust variance is not commonly used in the survival data analyses. PMID:24895154
NASA Technical Reports Server (NTRS)
Gyekenyesi, John P.; Nemeth, Noel N.
1987-01-01
The SCARE (Structural Ceramics Analysis and Reliability Evaluation) computer program on statistical fast fracture reliability analysis with quadratic elements for volume distributed imperfections is enhanced to include the use of linear finite elements and the capability of designing against concurrent surface flaw induced ceramic component failure. The SCARE code is presently coupled as a postprocessor to the MSC/NASTRAN general purpose, finite element analysis program. The improved version now includes the Weibull and Batdorf statistical failure theories for both surface and volume flaw based reliability analysis. The program uses the two-parameter Weibull fracture strength cumulative failure probability distribution model with the principle of independent action for poly-axial stress states, and Batdorf's shear-sensitive as well as shear-insensitive statistical theories. The shear-sensitive surface crack configurations include the Griffith crack and Griffith notch geometries, using the total critical coplanar strain energy release rate criterion to predict mixed-mode fracture. Weibull material parameters based on both surface and volume flaw induced fracture can also be calculated from modulus of rupture bar tests, using the least squares method with known specimen geometry and grouped fracture data. The statistical fast fracture theories for surface flaw induced failure, along with selected input and output formats and options, are summarized. An example problem to demonstrate various features of the program is included.
Mechanical Network in Titin Immunoglobulin from Force Distribution Analysis
Gräter, Frauke
Mechanical Network in Titin Immunoglobulin from Force Distribution Analysis Wolfram Stacklies1. , M, Stuttgart, Germany Abstract The role of mechanical force in cellular processes is increasingly revealed force propagates within proteins determines their mechanical behavior yet remains largely unknown. We
Charge distribution analysis of catalysts under simulated reaction conditions
Freund, F.
1992-01-01
Charge Distribution Analysis (CDA) is a technique for measuring mobile charge carriers in dielectric materials. CDA is based on dielectric polarization in an electric field gradient. The CDA apparatus is now under construction. 3 figs.
WATER DISTRIBUTION SYSTEM ANALYSIS: FIELD STUDIES, MODELING AND MANAGEMENT
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...
A Comparison of Distribution Free and Non-Distribution Free Factor Analysis Methods
ERIC Educational Resources Information Center
Ritter, Nicola L.
2012-01-01
Many researchers recognize that factor analysis can be conducted on both correlation matrices and variance-covariance matrices. Although most researchers extract factors from non-distribution free or parametric methods, researchers can also extract factors from distribution free or non-parametric methods. The nature of the data dictates the method…
Introduction to special section on Analysis of Zooplankton Distributions Using
Introduction to special section on Analysis of Zooplankton Distributions Using the Optical Plankton of zooplankton over broad expanses of space and for examining patterns in the size structure of zooplankton of Zooplankton Distributions Using the Optical Plankton Counter, J. Geophys. Res., 111, C05S01, doi:10
Distributed Antenna System: Performance Analysis in Multi-user Scenario
Dai, Lin
Distributed Antenna System: Performance Analysis in Multi-user Scenario Lin Dai Dept. Electronic--This paper provides a comparative study of the distributed antenna system (DAS) and the conventional co- located antenna system (CAS) in the multi-user scenario. It is demonstrated that thanks to the decrease
MultiState Load Models for Distribution System Analysis
Kevin P. Schneider; Jason C. Fuller; David P. Chassin
2011-01-01
Recent work in the field of distribution system anal- ysis has shown that the traditional method of peak load analysis is not adequate for the evaluation of emerging distribution system technologies. Voltage optimization, demand response, electric ve- hicle charging, and energy storage are examples of technologies with characteristics having daily, seasonal, and\\/or annual varia- tions. In addition to the seasonal
Silk Fiber Mechanics from Multiscale Force Distribution Analysis Murat Cetinkaya,
Gräter, Frauke
Silk Fiber Mechanics from Multiscale Force Distribution Analysis Murat Cetinkaya, Senbo Xiao, Bernd the molecular determinants for the extreme toughness of spider silk fibers. Our bottom-up computational approach of the internal strain distribution and load-carrying motifs in silk fibers on scales of both molecular
A note on positive distributions in Gaussian analysis
Yu. G. Kondrat'ev; Ludwig Streit; Werner Westerkamp
1995-01-01
We describe positive generalized functional in Gaussian analysis. We focus on the large distribution space (N)-1. It is shown that a positive distribution is represented by a measure with specific growth of its moments. Equivalently, this statement can be replaced by the integrability condition.
A Low Cost Distributed System for FEM Parallel Structural Analysis
Célio Oda Moretti; Túlio Nogueira Bittencourt; Luiz Fernando Martha
1998-01-01
\\u000a In this paper, a distributed computational system for finite element structural analysis and some strategies for improving\\u000a its efficiency are described. The system consists of a set of programs that performs the structural analysis in a distributed\\u000a computer network environment. This set is composed by a pre-processor, a post-processor, a program responsible for partitioning\\u000a the model in substructures, and by
Credibility in Context: An Analysis of Feature Distributions in Twitter
Hollerer, Tobias
Credibility in Context: An Analysis of Feature Distributions in Twitter John O'Donovan, Byungkyu@cs.rpi.edu Abstract--Twitter is a major forum for rapid dissemination of user-provided content in real time. As such focus on an analysis that highlights the utility of the individual features in Twitter such as hashtags
Elemental distribution analysis of urinary crystals
Y. M. Fazil Marickar; P. R. Lekshmi; Luxmi Varma; Peter Koshy
2009-01-01
Various crystals are seen in human urine. Some of them, particularly calcium oxalate dihydrate, are seen normally. Pathological\\u000a crystals indicate crystal formation initiating urinary stones. Unfortunately, many of the relevant crystals are not recognized\\u000a in light microscopic analysis of the urinary deposit performed in most of the clinical laboratories. Many crystals are not\\u000a clearly identifiable under the ordinary light microscopy.
Z. B. Zajac; R. Munoz-Carpena; K. Vanderlinden
2009-01-01
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
Bayesian inference based on dual generalized order statistics from the exponentiated Weibull model
NASA Astrophysics Data System (ADS)
Al Sobhi, Mashail M.
2015-02-01
Bayesian estimation for the two parameters and the reliability function of the exponentiated Weibull model are obtained based on dual generalized order statistics (DGOS). Also, Bayesian prediction bounds for future DGOS from exponentiated Weibull model are obtained. The symmetric and asymmetric loss functions are considered for Bayesian computations. The Markov chain Monte Carlo (MCMC) methods are used for computing the Bayes estimates and prediction bounds. The results have been specialized to the lower record values. Comparisons are made between Bayesian and maximum likelihood estimators via Monte Carlo simulation.
Ernest Y. Wu; J. Sune; W. Lai
2002-01-01
For pt. I see ibid., vol. 49, no. 12, p.2131 (2002).The Weibull slope measurement techniques described in Part I are used to determine Weibull slopes as function of thickness, voltage, and temperature. The effect of stress temperature and voltage on Weibull slopes is investigated over a wide range of voltage and temperatures for several different oxide thickness values. It was
Complex network analysis of water distribution systems
A. Yazdani; P. Jeffrey
2011-04-01
This paper explores a variety of strategies for understanding the formation, structure, efficiency and vulnerability of water distribution networks. Water supply systems are studied as spatially organized networks for which the practical applications of abstract evaluation methods are critically evaluated. Empirical data from benchmark networks are used to study the interplay between network structure and operational efficiency, reliability and robustness. Structural measurements are undertaken to quantify properties such as redundancy and optimal-connectivity, herein proposed as constraints in network design optimization problems. The role of the supply-demand structure towards system efficiency is studied and an assessment of the vulnerability to failures based on the disconnection of nodes from the source(s) is undertaken. The absence of conventional degree-based hubs (observed through uncorrelated non-heterogeneous sparse topologies) prompts an alternative approach to studying structural vulnerability based on the identification of network cut-sets and optimal connectivity invariants. A discussion on the scope, limitations and possible future directions of this research is provided.
Analysis of Distribution Level Residential Demand Response
Schneider, Kevin P.; Fuller, Jason C.; Chassin, David P.
2009-03-23
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.
Statistical analysis of bidirectional reflectance distribution functions
NASA Astrophysics Data System (ADS)
Zubiaga, Carlos J.; Belcour, Laurent; Bosch, Carles; Muñoz, Adolfo; Barla, Pascal
2015-03-01
Bidirectional Reflectance Distribution Functions (BRDFs) are commonly employed in Computer Graphics and Computer Vision to model opaque materials. On the one hand, a BRDF is a complex 4D function of both light and view directions, which should ensure reciprocity and energy conservation laws. On the other hand, when computing radiance reaching the eye from a surface point, the view direction is held fixed. In this respect, we are only interested in a 2D BRDF slice that acts as a filter on the local environment lighting. The goal of our work is to understand the statistical properties of such a filter as a function of viewing elevation. To this end, we have conducted a study of measured BRDFs where we have computed statistical moments for each viewing angle. We show that some moments are correlated together across dimensions and orders, while some others are close to zero and may safely be discarded. Our study opens the way to novel applications such as moment-based manipulation of measured BRDFs, material estimation and image-based material editing. It also puts empirical and physically-based material models in a new perspective, by revealing their effect as view-dependent filters.
Grammatical Analysis as a Distributed Neurobiological Function
Bozic, Mirjana; Fonteneau, Elisabeth; Su, Li; Marslen-Wilson, William D
2015-01-01
Language processing engages large-scale functional networks in both hemispheres. Although it is widely accepted that left perisylvian regions have a key role in supporting complex grammatical computations, patient data suggest that some aspects of grammatical processing could be supported bilaterally. We investigated the distribution and the nature of grammatical computations across language processing networks by comparing two types of combinatorial grammatical sequences—inflectionally complex words and minimal phrases—and contrasting them with grammatically simple words. Novel multivariate analyses revealed that they engage a coalition of separable subsystems: inflected forms triggered left-lateralized activation, dissociable into dorsal processes supporting morphophonological parsing and ventral, lexically driven morphosyntactic processes. In contrast, simple phrases activated a consistently bilateral pattern of temporal regions, overlapping with inflectional activations in L middle temporal gyrus. These data confirm the role of the left-lateralized frontotemporal network in supporting complex grammatical computations. Critically, they also point to the capacity of bilateral temporal regions to support simple, linear grammatical computations. This is consistent with a dual neurobiological framework where phylogenetically older bihemispheric systems form part of the network that supports language function in the modern human, and where significant capacities for language comprehension remain intact even following severe left hemisphere damage. PMID:25421880
Ghoniem, Nasr M.
- crackthatinitiatesthefractureandnotfromthevariation of the location of the critical microcrack. Utilizing the weakest-link theory, Weibull analysis. Keywords Brittleductile transition Á Fracture toughness Á Weibull analysis 1 IntroductionModeling the brittleductile transition in ferritic steels. Part II: analysis of scatter
Scaling Analysis of the Galaxy Distribution in the SSRS Catalog
A. Campos; R. Dominguez-Tenreiro; G. Yepes
1994-07-14
A detailed analysis of the galaxy distribution in the Southern Sky Redshift Survey (SSRS) by means of the multifractal or scaling formalism is presented. It is shown that galaxies cluster in different ways according to their morphological type as well as their size. Ellipticals are more clustered than spirals, even at scales up to 15 h$^{-1}$ Mpc, whereas no clear segregation between early and late spirals is found. It is also shown that smaller galaxies distribute more homogeneously than larger galaxies.
Influence of error distribution shape on process capability analysis
NASA Astrophysics Data System (ADS)
Asano, Masafumi; Ikeda, Takahiro
2010-03-01
In semiconductor manufacturing, process errors are likely to depart from normal distributions. For data violating the assumption of normality, classical process capability indices (PCIs) may be misleading in terms of the process behavior. To avoid this, we propose new PCIs with information on the skewness and the kurtosis of a given distribution. Based on a Monte Carlo simulation with various distributions, the formulae of the proposed PCIs were optimized. Compared with Johnson transformation or other approaches, our proposed method is simple in calculation. Therefore, it would have greater applicability for data analysis in semiconductor manufacturing.
First Experiences with LHC Grid Computing and Distributed Analysis
Fisk, Ian
2010-12-01
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.
Modeling and analysis of solar distributed generation
NASA Astrophysics Data System (ADS)
Ortiz Rivera, Eduardo Ivan
Recent changes in the global economy are creating a big impact in our daily life. The price of oil is increasing and the number of reserves are less every day. Also, dramatic demographic changes are impacting the viability of the electric infrastructure and ultimately the economic future of the industry. These are some of the reasons that many countries are looking for alternative energy to produce electric energy. The most common form of green energy in our daily life is solar energy. To convert solar energy into electrical energy is required solar panels, dc-dc converters, power control, sensors, and inverters. In this work, a photovoltaic module, PVM, model using the electrical characteristics provided by the manufacturer data sheet is presented for power system applications. Experimental results from testing are showed, verifying the proposed PVM model. Also in this work, three maximum power point tracker, MPPT, algorithms would be presented to obtain the maximum power from a PVM. The first MPPT algorithm is a method based on the Rolle's and Lagrange's Theorems and can provide at least an approximate answer to a family of transcendental functions that cannot be solved using differential calculus. The second MPPT algorithm is based on the approximation of the proposed PVM model using fractional polynomials where the shape, boundary conditions and performance of the proposed PVM model are satisfied. The third MPPT algorithm is based in the determination of the optimal duty cycle for a dc-dc converter and the previous knowledge of the load or load matching conditions. Also, four algorithms to calculate the effective irradiance level and temperature over a photovoltaic module are presented in this work. The main reasons to develop these algorithms are for monitoring climate conditions, the elimination of temperature and solar irradiance sensors, reductions in cost for a photovoltaic inverter system, and development of new algorithms to be integrated with maximum power point tracking algorithms. Finally, several PV power applications will be presented like circuit analysis for a load connected to two different PV arrays, speed control for a do motor connected to a PVM, and a novel single phase photovoltaic inverter system using the Z-source converter.
The negative binomial–beta Weibull regression model to predict the cure of prostate cancer
Edwin M. M. Ortega; Gauss M. Cordeiro; Michael W. Kattan
2011-01-01
In this article, for the first time, we propose the negative binomial–beta Weibull (BW) regression model for studying the recurrence of prostate cancer and to predict the cure fraction for patients with clinically localized prostate cancer treated by open radical prostatectomy. The cure model considers that a fraction of the survivors are cured of the disease. The survival function for
The negative binomial–beta Weibull regression model to predict the cure of prostate cancer
Edwin M. M. Ortega; Gauss M. Cordeiro; Michael W. Kattan
2012-01-01
In this article, for the first time, we propose the negative binomial–beta Weibull (BW) regression model for studying the recurrence of prostate cancer and to predict the cure fraction for patients with clinically localized prostate cancer treated by open radical prostatectomy. The cure model considers that a fraction of the survivors are cured of the disease. The survival function for
An Example of Data Technology Product: A Control Chart for Weibull Processes
Pasquale Erto; Giuliana Pallotta; Sung H. Park
2008-01-01
This work proposes a new Shewhart-type control chart of the Weibull percentile (i.e. the reliable life) as a practical example of a product attained following the Data Technology (DT) approach. DT is briefly introduced as a new discipline defined apart from Information Technology (IT). Following this approach, some specific Bayes estimators are selected from literature and then used to build
Second-order statistics of maximal-ratio and equal-gain combining in Weibull fading
Gustavo Fraidenraich; Michel D. Yacoub; J. C. S. Santos Filho
2005-01-01
Exact expressions for the level crossing rate and average fade duration of M-branch equal-gain and maximal-ratio combining systems in a Weibull fading environment are presented. The expressions apply to unbalanced, nonidentical, independent diversity channels. In addition, new closed-form solutions for some special cases are obtained.
Examing the Poisson-Weibull Generalized Model for Analyzing Crash Data
Cheng, Lingzi
2012-10-19
data are characterized by low sample mean and small sample size. The main research objective of this thesis is to develop a new statistical method namely, Poisson-Weibull (PW) Generalized Linear Model (GLM) to analyze vehicle crash data and to evaluate...
EXPERIMENTAL DESIGN STRATEGY FOR THE WEIBULL DOSE RESPONSE MODEL (JOURNAL VERSION)
The objective of the research was to determine optimum design point allocation for estimation of relative yield losses from ozone pollution when the true and fitted yield-ozone dose response relationship follows the Weibull. The optimum design is dependent on the values of the We...
Entropy Methods For Univariate Distributions in Decision Analysis
NASA Astrophysics Data System (ADS)
Abbas, Ali E.
2003-03-01
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.
Statistical Distributions of Hydraulic Conductivity from Reliability Analysis Data
C. M. O. Nwaiwu
2009-01-01
This paper describes a first-order reliability-based analysis to identify the best-fit probability distributions for hydraulic\\u000a conductivity. The analysis involved the use of existing hydraulic conductivity model developed from laboratory data and applied\\u000a to lateritic soils, considering variations in soil parameters. Plots of reliability indices versus coefficients of variation\\u000a were first made for hydraulic conductivity as well as for initial degree
ANALYSIS OF DISTRIBUTION FEEDER LOSSES DUE TO ADDITION OF DISTRIBUTED PHOTOVOLTAIC GENERATORS
Tuffner, Francis K.; Singh, Ruchi
2011-08-09
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%).
GIS-based poverty and population distribution analysis in China
NASA Astrophysics Data System (ADS)
Cui, Jing; Wang, Yingjie; Yan, Hong
2009-07-01
Geographically, poverty status is not only related with social-economic factors but also strongly affected by geographical environment. In the paper, GIS-based poverty and population distribution analysis method is introduced for revealing their regional differences. More than 100000 poor villages and 592 national key poor counties are chosen for the analysis. The results show that poverty distribution tends to concentrate in most of west China and mountainous rural areas of mid China. Furthermore, the fifth census data are overlaid to those poor areas in order to gain its internal diversity of social-economic characteristics. By overlaying poverty related social-economic parameters, such as sex ratio, illiteracy, education level, percentage of ethnic minorities, family composition, finding shows that poverty distribution is strongly correlated with high illiteracy rate, high percentage minorities, and larger family member.
Individual patterns of motor deficits evident in movement distribution analysis
Huang, Felix C.; Patton, James L.
2015-01-01
Recent studies in rehabilitation have shown potential benefits of patient-initiated exploratory practice. Such findings, however, lead to new challenges in how to quantify and interpret movement patterns. We posit that changes in coordination are most evident in statistical distributions of movements. In a test on 10 chronic stroke subjects practicing for 3 days, we found that inter-quartile range of motion did not show improvement. However, a multivariate Gaussians analysis required more complexity at the end of training. Beyond simply characterizing movement, linear discriminant classification of each patient’s movement distribution also identified that each patient’s motor deficit left a unique signature. The greatest distinctions were observed in the space of accelerations (rather than position or velocity). These results suggest that unique deficits are best detected with such a distribution analysis, and also point to the need for customized interventions that consider such patient-specific motor deficits. PMID:24187248
Analysis of Policy Anomalies on Distributed Network Security Setups
Garcia-Alfaro, Joaquin
Analysis of Policy Anomalies on Distributed Network Security Setups J. G. Alfaro1,2, F. Cuppens1.Garcia-Alfaro@deic.uab.es Abstract: The use of different network security components, such as firewalls and network intrusion corporate networks. On the one hand, firewalls are traditional security components which provide means
Pointers and linked lists in electric power distribution circuit analysis
R. P. Broadwater; J. C. Thompson; T. E. McDermott
1991-01-01
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
Distributed data analysis system for CMD-3 detector
NASA Astrophysics Data System (ADS)
Gaiazov, S. E.; Banzarov, V. S.; Ignatov, F. V.; Logashenko, I. B.; Pirogov, S. A.; Sukharev, A. M.; Zaytsev, A. S.
2014-08-01
The architecture and the implementation of the distributed data analysis system for CMD-3 detector are described. The system effectively uses available heterogeneous resources for the data storing and processing. The system is fully implemented and operational. A brief overview of the obtained characteristics of the system is also presented.
Fourier Analysis, Distribution Theory, and Wavelets Bengt Ove Turesson1
Nair, M.Thamban
Fourier Analysis, Distribution Theory, and Wavelets Bengt Ove Turesson1 March 13, 2012 1 . . . . . . . . . . . . . . . . . . . . . . . . . . 13 II Fourier Series 14 2 L1 -theory for Fourier Series 15 2.1 Function Spaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.2 Fourier Series and Fourier Coefficients . . . . . . . . . . . . . . . . . 15 2.3 Trigonometric
Analysis of security protocols for authentication in distributed systems
H. A. Eneh; O. Gemikonakli
2005-01-01
Research works on the analysis and the development of authentication protocols frequently adopt the linear software development approach and are based on certain non-extensible assumptions (Tobler and Hutchison 2004), (Grob 2003), (Harbitter and Menasce 2002). This paper is part of an ongoing work regarding the development of a pre-emptive security mechanism for networks and distributed systems. We present in this
Combining Probability Distributions From Experts in Risk Analysis
Robert T. Clemen; Robert L. Winkler
1999-01-01
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
REGIONAL FLOOD FREQUENCY ANALYSIS WITH A THEORETICALLY DERIVED DISTRIBUTION FUNCTION
Poggi, Davide
REGIONAL FLOOD FREQUENCY ANALYSIS WITH A THEORETICALLY DERIVED DISTRIBUTION FUNCTION P. CLAPS1 , M.iacobellis@poliba.it, Via E. Orabona, 4, 70125, Bari, Italy ABSTRACT The estimation of flood frequency curves in ungauged to estimation of flood quantiles, and for transferring hydrological information between basins. In this context
Systematical Analysis on Angular Distribution of Bremsstrahlung Radiation
Otgooloi, B.; Enkhbat, N. [Nuclear Research Center, National University of Mongolia, Ulaanbaatar (Mongolia)
2009-03-31
The systematic analysis has been made the measurement results of the relative angular distribution of gamma quantium with 11 divide 16 MeV energy using experimental data of Ta, W, Cu, Mo and Ti targets with various radiating lengths thicknesses.
Distributed PC Based Routers: Bottleneck Analysis and Architecture Proposal
Distributed PC Based Routers: Bottleneck Analysis and Architecture Proposal A. J. Khan lIT Bombay R Abstract-Recent research in the different functional areas of modern routers have made proposals that can the advances made by researchers. We therefore examine the ability of a personal computer to act as a router
Analysis of AOA-TOA signal distribution in indoor environments
E. Tsalolihin; I. Bilik; N. Blaunstein; S. Shakya
2011-01-01
This work presents theoretical and experimental analysis of radio signals propagation in LOS and NLOS indoor propagation conditions. Specifically, propagation conditions in straight corridor and adjacent rooms are analysed. A statistical multi-parametric approach that was previously used in urban propagation conditions is adapted to the modelling of indoor communication channels. The model of the received signal distribution in the joint
Distributed Portfolio and Investment Risk Analysis on Global Grids
Buyya, Rajkumar
1 Distributed Portfolio and Investment Risk Analysis on Global Grids Rafael Moreno-Vozmediano2 on a higher level of risk. Investors aim to optimise their investment portfolio in order to minimise the risk and maximise the returns. However, there are many variables involved in portfolio optimization and therefore
Analysis of Hawaii Biomass Energy Resources for Distributed Energy Applications
Analysis of Hawaii Biomass Energy Resources for Distributed Energy Applications Prepared for State of Hawaii Department of Business, Economic Development and Tourism by University of Hawaii Hawaii Natural of Tables Table 1-A. Analyses of biomass materials found in the State of Hawaii
Modal analysis of optical fibers with symmetrically distributed nonuniform cores
Naoto Kishi; K. Tayama; E. Yamashita
1996-01-01
This paper describes the modal analysis of optical fibers with symmetrically distributed multiple cores. Each core has an identical, axially symmetrical, and nonuniform refractive index profile. Group theoretical approach is applied to treat the symmetry of the waveguide structure. The point-matching method combined with the staircase-approximation method is used to take into account complex boundary conditions and complex refractive index
Rapid Analysis of Mass Distribution of Radiation Shielding
NASA Technical Reports Server (NTRS)
Zapp, Edward
2007-01-01
Radiation Shielding Evaluation Toolset (RADSET) is a computer program that rapidly calculates the spatial distribution of mass of an arbitrary structure for use in ray-tracing analysis of the radiation-shielding properties of the structure. RADSET was written to be used in conjunction with unmodified commercial computer-aided design (CAD) software that provides access to data on the structure and generates selected three-dimensional-appearing views of the structure. RADSET obtains raw geometric, material, and mass data on the structure from the CAD software. From these data, RADSET calculates the distribution(s) of the masses of specific materials about any user-specified point(s). The results of these mass-distribution calculations are imported back into the CAD computing environment, wherein the radiation-shielding calculations are performed.
Analyzing Distributed Functions in an Integrated Hazard Analysis
NASA Technical Reports Server (NTRS)
Morris, A. Terry; Massie, Michael J.
2010-01-01
Large scale integration of today's aerospace systems is achievable through the use of distributed systems. Validating the safety of distributed systems is significantly more difficult as compared to centralized systems because of the complexity of the interactions between simultaneously active components. Integrated hazard analysis (IHA), a process used to identify unacceptable risks and to provide a means of controlling them, can be applied to either centralized or distributed systems. IHA, though, must be tailored to fit the particular system being analyzed. Distributed systems, for instance, must be analyzed for hazards in terms of the functions that rely on them. This paper will describe systems-oriented IHA techniques (as opposed to traditional failure-event or reliability techniques) that should be employed for distributed systems in aerospace environments. Special considerations will be addressed when dealing with specific distributed systems such as active thermal control, electrical power, command and data handling, and software systems (including the interaction with fault management systems). Because of the significance of second-order effects in large scale distributed systems, the paper will also describe how to analyze secondary functions to secondary functions through the use of channelization.
Molecular Isotopic Distribution Analysis (MIDAs) with Adjustable Mass Accuracy
NASA Astrophysics Data System (ADS)
Alves, Gelio; Ogurtsov, Aleksey Y.; Yu, Yi-Kuo
2014-01-01
In this paper, we present Molecular Isotopic Distribution Analysis (MIDAs), a new software tool designed to compute molecular isotopic distributions with adjustable accuracies. MIDAs offers two algorithms, one polynomial-based and one Fourier-transform-based, both of which compute molecular isotopic distributions accurately and efficiently. The polynomial-based algorithm contains few novel aspects, whereas the Fourier-transform-based algorithm consists mainly of improvements to other existing Fourier-transform-based algorithms. We have benchmarked the performance of the two algorithms implemented in MIDAs with that of eight software packages (BRAIN, Emass, Mercury, Mercury5, NeutronCluster, Qmass, JFC, IC) using a consensus set of benchmark molecules. Under the proposed evaluation criteria, MIDAs's algorithms, JFC, and Emass compute with comparable accuracy the coarse-grained (low-resolution) isotopic distributions and are more accurate than the other software packages. For fine-grained isotopic distributions, we compared IC, MIDAs's polynomial algorithm, and MIDAs's Fourier transform algorithm. Among the three, IC and MIDAs's polynomial algorithm compute isotopic distributions that better resemble their corresponding exact fine-grained (high-resolution) isotopic distributions. MIDAs can be accessed freely through a user-friendly web-interface at http://www.ncbi.nlm.nih.gov/CBBresearch/Yu/midas/index.html.
Analysis of exposure biomarker relationships with the Johnson SBB distribution.
Flynn, Michael R
2007-08-01
Application of the Johnson bivariate S(B) distribution, or alternatively the S(BB) distribution, is presented here as a tool for the analysis of concentration data and in particular for characterizing the relationship between exposures and biomarkers. Methods for fitting the marginal S(B) distributions are enhanced by maximizing the Shapiro-Wilk W statistic. The subsequent goodness of fit for the S(BB) distribution is evaluated with a multivariate Z statistic. Median regression results are extended here with methods for calculating the mean and standard deviation of the conditional array distributions. Application of these methods to the evaluation of the relationship between exposure to airborne bromopropane and the biomarker of serum bromide concentration suggests that the S(BB) distribution may be useful in stratifying workers by exposure based on using a biomarker. A comparison with the usual two-parameter log-normal approach shows that in some cases the S(BB) distribution may offer advantages. PMID:17693427
EVA Tutorial #3 ISSUES ARISING IN EXTREME VALUE ANALYSIS
Katz, Richard
1 EVA Tutorial #3 ISSUES ARISING IN EXTREME VALUE ANALYSIS Rick Katz Institute for Mathematics mean & unit variance) -- Fisher & Tippett (1928) proposed Weibull type of GEV as penultimate(n) (2 ln n ) 1/2 , for large n Penultimate approximation is Weibull type with n - 1 / (2 ln n
Distributed intelligent data analysis in diabetic patient management.
Bellazzi, R.; Larizza, C.; Riva, A.; Mira, A.; Fiocchi, S.; Stefanelli, M.
1996-01-01
This paper outlines the methodologies that can be used to perform an intelligent analysis of diabetic patients' data, realized in a distributed management context. We present a decision-support system architecture based on two modules, a Patient Unit and a Medical Unit, connected by telecommunication services. We stress the necessity to resort to temporal abstraction techniques, combined with time series analysis, in order to provide useful advice to patients; finally, we outline how data analysis and interpretation can be cooperatively performed by the two modules. PMID:8947655
Multi-State Load Models for Distribution System Analysis
Schneider, Kevin P.; Fuller, Jason C.; Chassin, David P.
2011-11-01
Recent work in the field of distribution system analysis has shown that the traditional method of peak load analysis is not adequate for the analysis of emerging distribution system technologies. Voltage optimization, demand response, electric vehicle charging, and energy storage are examples of technologies with characteristics having daily, seasonal, and/or annual variations. In addition to the seasonal variations, emerging technologies such as demand response and plug in electric vehicle charging have the potential to send control signals to the end use loads which will affect how they consume energy. In order to support time-series analysis over different time frames and to incorporate potential control signal inputs it is necessary to develop detailed end use load models which accurately represent the load under various conditions, and not just during the peak load period. This paper will build on previous work on detail end use load modeling in order to outline the method of general multi-state load models for distribution system analysis.
Reliability Estimation and Failure Analysis of Multilayer Ceramic Chip Capacitors
NASA Astrophysics Data System (ADS)
Yang, Seok Jun; Kim, Jin Woo; Ryu, Dong Su; Kim, Myung Soo; Jang, Joong Soon
This paper presents the failure analysis and the reliability estimation of a multilayer ceramic chip capacitor. For the failed samples used in an automobile engine control unit, failure analysis was made to identify the root cause of failure and it was shown that the migration and the avalanche breakdown were the dominant failure mechanisms. Next, an accelerated life testing was designed to estimate the life of the MLCC. It is assumed that Weibull lifetime distribution and the life-stress relationship proposed Prokopowicz and Vaskas. The life-stress relationship and the acceleration factor are estimated by analyzing the accelerated life test data.
Extreme Value Analysis and Ventures into Space and Time
Gilleland, Eric
of Extreme Value df's #12;Copyright NCAR 2013 Extreme Value Analysis Weibull dfExtreme Value Analysis and Ventures into Space and Time 15 Center for Atmospheric Research Copyright NCAR 2013 #12;Extreme Value Analysis
Integrating software architectures for distributed simulations and simulation analysis communities.
Goldsby, Michael E.; Fellig, Daniel; Linebarger, John Michael; Moore, Patrick Curtis; Sa, Timothy J.; Hawley, Marilyn F.
2005-10-01
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.
Specification of distribution functions for magnetic hysteresis modeling
A. Pruksanubal
2009-01-01
This paper describes the combination of different statistical distributions to apply in the Preisach hysteresis model. The model is able to represent the hysteresis property of the ferromagnetic material if its distribution function is well determined. Various distributions, such as Gaussian, Weibull, Cauchy, Laplace, Rayleigh, etc., are combined to produce different distribution functions and to simulate the hysteresis loops. Finally,
Influence Of Lateral Load Distributions On Pushover Analysis Effectiveness
Colajanni, P.; Potenzone, B. [Dipartimento di Ingegneria Civile, Universita di Messina, Contrada Di Dio, S. Agata, 98166 Messina (Italy)
2008-07-08
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.
A description of the failure distributions of selected Minuteman 3 guidance system electronic cards
NASA Astrophysics Data System (ADS)
Sisk, Albert E.
1986-09-01
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.
Towards Distributed Visualization and Analysis of Large Flow Data
NASA Astrophysics Data System (ADS)
Hege, Hans-Christian; Weinkauf, Tino; Prohaska, Steffen; Hutanu, Andrei
Fluid dynamics applications require a good understanding of the underlying physical phenomena. Therefore, effective procedures are necessary for analyzing and visualizing the various physical fields. Beside interactive and perceptually efficient techniques for visualizing flow fields directly, there is strong demand for methods that uncover hidden flow structures. Some recently developed feature based visual analysis methods are exemplarily presented. Fluid flow data typically are large and often are stored remotely or distributedly. The interactive visual analysis of such large data sets requires new software architectures ─ ideally utilizing emerging Grid standards. We discuss such architectures and report on specific software realizations.
Lambert W-function in Statistical Distributions and Reliability Analysis
P. N. Rathie
Lambert W-function is relatively a new special function with applications in various areas of mathematics and engineering. In this paper, some new applications of W-function are given for logarithmic series and generalized gamma (one and two sided) distributions and for optimal maintenance time for repairable systems in Reliability Analysis. Computation of W-function, with good precision, is already available in Mathematica
Electrical Power Distribution and Control Modeling and Analysis
NASA Technical Reports Server (NTRS)
Fu, Johnny S.; Liffring, Mark; Mehdi, Ishaque S.
2001-01-01
This slide presentation reviews the use of Electrical Power Distribution and Control (EPD&C) Modeling and how modeling can support analysis. The presentation discusses using the EASY5 model to simulate and analyze the Space Shuttle Electric Auxiliary Power Unit. Diagrams of the model schematics are included, as well as graphs of the battery cell impedance, hydraulic load dynamics, and EPD&C response to hydraulic load variations.
Distributive analysis of rural land size and price relationships
Rothe, Robert Joseph
1980-01-01
DISTRIBUTIFE ANALTSIS OF RURAL LAND SIZE PRICE RELATIONSHIPS A Thesis by Robert Joseph Roche Submitted to the Graduate College of. Texas ASM University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE August... 1980 Major Subject: Agricultural Economics DISTRIBUTIVE ANALYSIS OF RURAL LAND SIZE AND PRICE RELATIONSHIPS A Thesis by Robert Joseph Rothe Approved as to style and content by: (Chairman of Committee) (Me er) Member) (Head o Department) August...
Analysis of size dependence of ceramic fiber and whisker strength
Zhu, Y.T.; Blumenthal, W.R.; Taylor, S.T.; Lowe, T.C. [Los Alamos National Lab., NM (United States). Materials Science and Technology Div.; Zhou, B. [Chinese Academy of Sciences, Shenyang (China). Inst. of Metal Research
1997-06-01
The strengths of ceramic fibers and whiskers have been observed to increase with decreasing fiber diameter and length. Typically, both surface flaws and volume flaws exist in ceramic fibers and whiskers, which make it impossible to characterize the strength dependence of both the diameter and the length with a single-modal Weibull distribution function. The data also show that the single-modal Weibull distribution is inadequate to characterize the strength of fibers with varying diameters even in the case of a constant fiber length. In addition, experimental data also show that, for sapphire whiskers whose surface flaws were removed by chemical polishing, the whisker strength has a much stronger size dependence on diameter than predicted by the single-modal Weibull function, which indicates that factors other than those characterized by the Weibull function also play a role in the strength of sapphire whiskers. In this paper, the factors affecting the strengths of ceramic fibers and whiskers are analyzed in terms of Weibull statistics, fracture mechanics, and flaw size density variation with varying fiber diameters. A three-parameter modified Weibull distribution, which combines the above strength-affecting factors, is proposed to characterize both the diameter and the length dependence for ceramic fibers and whiskers with or without surface flaws. Characterization of the strength data of sapphire whiskers and Nicalon SiC fibers with varying diameters shows the validity of the modified Weibull distribution function.
Distributions of Autocorrelated First-Order Kinetic Outcomes: Illness Severity.
Englehardt, James D
2015-01-01
Many complex systems produce outcomes having recurring, power law-like distributions over wide ranges. However, the form necessarily breaks down at extremes, whereas the Weibull distribution has been demonstrated over the full observed range. Here the Weibull distribution is derived as the asymptotic distribution of generalized first-order kinetic processes, with convergence driven by autocorrelation, and entropy maximization subject to finite positive mean, of the incremental compounding rates. Process increments represent multiplicative causes. In particular, illness severities are modeled as such, occurring in proportion to products of, e.g., chronic toxicant fractions passed by organs along a pathway, or rates of interacting oncogenic mutations. The Weibull form is also argued theoretically and by simulation to be robust to the onset of saturation kinetics. The Weibull exponential parameter is shown to indicate the number and widths of the first-order compounding increments, the extent of rate autocorrelation, and the degree to which process increments are distributed exponential. In contrast with the Gaussian result in linear independent systems, the form is driven not by independence and multiplicity of process increments, but by increment autocorrelation and entropy. In some physical systems the form may be attracting, due to multiplicative evolution of outcome magnitudes towards extreme values potentially much larger and smaller than control mechanisms can contain. The Weibull distribution is demonstrated in preference to the lognormal and Pareto I for illness severities versus (a) toxicokinetic models, (b) biologically-based network models, PMID:26061263
Distribution System Reliability Analysis for Smart Grid Applications
NASA Astrophysics Data System (ADS)
Aljohani, Tawfiq Masad
Reliability of power systems is a key aspect in modern power system planning, design, and operation. The ascendance of the smart grid concept has provided high hopes of developing an intelligent network that is capable of being a self-healing grid, offering the ability to overcome the interruption problems that face the utility and cost it tens of millions in repair and loss. To address its reliability concerns, the power utilities and interested parties have spent extensive amount of time and effort to analyze and study the reliability of the generation and transmission sectors of the power grid. Only recently has attention shifted to be focused on improving the reliability of the distribution network, the connection joint between the power providers and the consumers where most of the electricity problems occur. In this work, we will examine the effect of the smart grid applications in improving the reliability of the power distribution networks. The test system used in conducting this thesis is the IEEE 34 node test feeder, released in 2003 by the Distribution System Analysis Subcommittee of the IEEE Power Engineering Society. The objective is to analyze the feeder for the optimal placement of the automatic switching devices and quantify their proper installation based on the performance of the distribution system. The measures will be the changes in the reliability system indices including SAIDI, SAIFI, and EUE. The goal is to design and simulate the effect of the installation of the Distributed Generators (DGs) on the utility's distribution system and measure the potential improvement of its reliability. The software used in this work is DISREL, which is intelligent power distribution software that is developed by General Reliability Co.
Componential distribution analysis of food using near infrared ray image
NASA Astrophysics Data System (ADS)
Yamauchi, Hiroki; Kato, Kunihito; Yamamoto, Kazuhiko; Ogawa, Noriko; Ohba, Kimie
2008-11-01
The components of the food related to the "deliciousness" are usually evaluated by componential analysis. The component content and type of components in the food are determined by this analysis. However, componential analysis is not able to analyze measurements in detail, and the measurement is time consuming. We propose a method to measure the two-dimensional distribution of the component in food using a near infrared ray (IR) image. The advantage of our method is to be able to visualize the invisible components. Many components in food have characteristics such as absorption and reflection of light in the IR range. The component content is measured using subtraction between two wavelengths of near IR light. In this paper, we describe a method to measure the component of food using near IR image processing, and we show an application to visualize the saccharose in the pumpkin.
Qualitative Analysis of Distributed Physical Systems with Applications to Control Synthesis \\Lambda
Bailey-Kellogg, Chris
Qualitative Analysis of Distributed Physical Systems with Applications to Control Synthesis \\Lambda ature distribution, air flow, and acoustic waves, are described as continuous, distributed parameter fields. Analyzing and controlling these physical processes and systems are common tasks in many
Roy, Sourajeet
, delay effects, partitioning algorithms, electromagnetic transients, transmission lines. I. INTRODUCTIONFast Electromagnetic Interference Analysis of Distributed Networks using Longitudinal Partitioning -- In this paper, a waveform relaxation algorithm for the fast electromagnetic interference analysis of distributed
Probabilistic Life and Reliability Analysis of Model Gas Turbine Disk
NASA Technical Reports Server (NTRS)
Holland, Frederic A.; Melis, Matthew E.; Zaretsky, Erwin V.
2002-01-01
In 1939, W. Weibull developed what is now commonly known as the "Weibull Distribution Function" primarily to determine the cumulative strength distribution of small sample sizes of elemental fracture specimens. In 1947, G. Lundberg and A. Palmgren, using the Weibull Distribution Function developed a probabilistic lifing protocol for ball and roller bearings. In 1987, E. V. Zaretsky using the Weibull Distribution Function modified the Lundberg and Palmgren approach to life prediction. His method incorporates the results of coupon fatigue testing to compute the life of elemental stress volumes of a complex machine element to predict system life and reliability. This paper examines the Zaretsky method to determine the probabilistic life and reliability of a model gas turbine disk using experimental data from coupon specimens. The predicted results are compared to experimental disk endurance data.
Growing axons analysis by using Granulometric Size Distribution
NASA Astrophysics Data System (ADS)
Gonzalez, Mariela A.; Ballarin, Virginia L.; Rapacioli, Melina; Celín, A. R.; Sánchez, V.; Flores, V.
2011-09-01
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.
Performance Analysis of an Actor-Based Distributed Simulation
NASA Technical Reports Server (NTRS)
Schoeffler, James D.
1998-01-01
Object-oriented design of simulation programs appears to be very attractive because of the natural association of components in the simulated system with objects. There is great potential in distributing the simulation across several computers for the purpose of parallel computation and its consequent handling of larger problems in less elapsed time. One approach to such a design is to use "actors", that is, active objects with their own thread of control. Because these objects execute concurrently, communication is via messages. This is in contrast to an object-oriented design using passive objects where communication between objects is via method calls (direct calls when they are in the same address space and remote procedure calls when they are in different address spaces or different machines). This paper describes a performance analysis program for the evaluation of a design for distributed simulations based upon actors.
Bayesian models for DNA microarray data analysis
Lee, Kyeong Eun
2005-08-29
. Additionally, we consider the wellknown Weibull regression and semiparametric proportional hazards (PH) models for survival analysis. With microarray data, we need to consider the case where the number of covariates p exceeds the number of samples n. Speci...
Time series power flow analysis for distribution connected PV generation.
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
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.
Analysis of dilepton angular distributions in a parity breaking medium
NASA Astrophysics Data System (ADS)
Andrianov, A. A.; Andrianov, V. A.; Espriu, D.; Planells, X.
2014-08-01
We investigate how local parity breaking due to large topological fluctuations may affect hadron physics. A modified dispersion relation is derived for the lightest vector mesons ? and ?. They exhibit a mass splitting depending on their polarization. We present a detailed analysis of the angular distribution associated to the lepton pairs created from these mesons searching for polarization dependencies. We propose two angular variables that carry information related to the parity breaking effect. Possible signatures for experimental detection of local parity breaking that could potentially be seen by the PHENIX and STAR collaborations are discussed.
Analysis of dilepton angular distributions in a parity breaking medium
Alexander A. Andrianov; Vladimir A. Andrianov; Domenec Espriu; Xumeu Planells
2014-07-21
We investigate how local parity breaking (LPB) due to large topological fluctuations may affect hadron physics. A distorted dispersion relation is derived for the lightest vector mesons $\\rho$ and $\\omega$. They are characterised by a mass splitting depending on their polarization. We present a detailed analysis of the angular distribution associated to the lepton pairs created from these mesons searching for polarization dependencies. Two angular variables are found to carry the main information related to the parity breaking effect. Possible signatures for experimental detection of local parity breaking that could potentially be seen by the PHENIX and STAR collaborations are discussed.
A comprehensive study of distribution laws for the fragments of Košice meteorite
NASA Astrophysics Data System (ADS)
Gritsevich, Maria; Vinnikov, Vladimir; Kohout, TomáÅ.¡; Tóth, Juraj; Peltoniemi, Jouni; Turchak, Leonid; Virtanen, Jenni
2014-03-01
In this study, we conduct a detailed analysis of the Košice meteorite fall (February 28, 2010), to derive a reliable law describing the mass distribution among the recovered fragments. In total, 218 fragments of the Košice meteorite, with a total mass of 11.285 kg, were analyzed. Bimodal Weibull, bimodal Grady, and bimodal lognormal distributions are found to be the most appropriate for describing the Košice fragmentation process. Based on the assumption of bimodal lognormal, bimodal Grady, bimodal sequential, and bimodal Weibull fragmentation distributions, we suggest that, prior to further extensive fragmentation in the lower atmosphere, the Košice meteoroid was initially represented by two independent pieces with cumulative residual masses of approximately 2 and 9 kg, respectively. The smaller piece produced about 2 kg of multiple lightweight meteorite fragments with the mean around 12 g. The larger one resulted in 9 kg of meteorite fragments, recovered on the ground, including the two heaviest pieces of 2.374 kg and 2.167 kg with the mean around 140 g. Based on our investigations, we conclude that two to three larger fragments of 500-1000 g each should exist, but were either not recovered or not reported by illegal meteorite hunters.
NASA Astrophysics Data System (ADS)
Sun, Huarui; Bajo, Miguel Montes; Uren, Michael J.; Kuball, Martin
2015-01-01
Gate leakage degradation of AlGaN/GaN high electron mobility transistors under OFF-state stress is investigated using a combination of electrical, optical, and surface morphology characterizations. The generation of leakage "hot spots" at the edge of the gate is found to be strongly temperature accelerated. The time for the formation of each failure site follows a Weibull distribution with a shape parameter in the range of 0.7-0.9 from room temperature up to 120 °C. The average leakage per failure site is only weakly temperature dependent. The stress-induced structural degradation at the leakage sites exhibits a temperature dependence in the surface morphology, which is consistent with a surface defect generation process involving temperature-associated changes in the breakdown sites.
Analysis of Fuel Ethanol Transportation Activity and Potential Distribution Constraints
Das, Sujit [ORNL; Peterson, Bruce E [ORNL; Chin, Shih-Miao [ORNL
2010-01-01
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.
Two-dimensional fluorescence intensity distribution analysis: theory and applications.
Kask, P; Palo, K; Fay, N; Brand, L; Mets, U; Ullmann, D; Jungmann, J; Pschorr, J; Gall, K
2000-01-01
A method of sample analysis is presented which is based on fitting a joint distribution of photon count numbers. In experiments, fluorescence from a microscopic volume containing a fluctuating number of molecules is monitored by two detectors, using a confocal microscope. The two detectors may have different polarizational or spectral responses. Concentrations of fluorescent species together with two specific brightness values per species are determined. The two-dimensional fluorescence intensity distribution analysis (2D-FIDA), if used with a polarization cube, is a tool that is able to distinguish fluorescent species with different specific polarization ratios. As an example of polarization studies by 2D-FIDA, binding of 5'-(6-carboxytetramethylrhodamine) (TAMRA)-labeled theophylline to an anti-theophylline antibody has been studied. Alternatively, if two-color equipment is used, 2D-FIDA can determine concentrations and specific brightness values of fluorescent species corresponding to individual labels alone and their complex. As an example of two-color 2D-FIDA, binding of TAMRA-labeled somatostatin-14 to the human type-2 high-affinity somatostatin receptors present in stained vesicles has been studied. The presented method is unusually accurate among fluorescence fluctuation methods. It is well suited for monitoring a variety of molecular interactions, including receptors and ligands or antibodies and antigens. PMID:10733953
Providing Complete Distribution Function Analysis with NUBEAM FGen
NASA Astrophysics Data System (ADS)
Stark, Casey; McCune, Douglas; Feibush, Eliot
2009-11-01
The TRANSP libraries provide many robust tools for analyzing tokamak plasmas. The development of this long-standing code has focused on physics modeling and producing efficient plasma calculations. In order to make these powerful libraries accessible to more scientists, parts of the code have been incorporated into web services, which can be run using the ElVis scientific graphics display. We present NUBEAM FGen, a new graphical web service interface focusing on distribution function (DF) simulation and analysis now integrated into ElVis. This interface can acquire TRANSP run data and given simulation parameters (a time of interest, duration, number of particles, etc.), will run a NUBEAM simulation on extracted Plasma State files. This simulation outputs the full distribution function in energy, pitch, x, and theta space. The user can analyze the DF data with an interactive getfbm session, allowing them to visualize the DF with various plots (contour, slice, 3D, etc.). Users can also download the output for their own processing. The ease of this new approach to DF analysis will allow a much wider audience to utilize the DF tools provided by TRANSP in their own research.
Preliminary analysis of hub and spoke air freight distribution system
NASA Technical Reports Server (NTRS)
Whitehead, A. H., Jr.
1978-01-01
A brief analysis is made of the hub and spoke air freight distribution system which would employ less than 15 hub centers world wide with very large advanced distributed-load freighters providing the line-haul delivery between hubs. This system is compared to a more conventional network using conventionally-designed long-haul freighters which travel between numerous major airports. The analysis calculates all of the transportation costs, including handling charges and pickup and delivery costs. The results show that the economics of the hub/spoke system are severely compromised by the extensive use of feeder aircraft to deliver cargo into and from the large freighter terminals. Not only are the higher costs for the smaller feeder airplanes disadvantageous, but their use implies an additional exchange of cargo between modes compared to truck delivery. The conventional system uses far fewer feeder airplanes, and in many cases, none at all. When feeder aircraft are eliminated from the hub/spoke system, however, that system is universally more economical than any conventional system employing smaller line-haul aircraft.
BME analysis of spatiotemporal particulate matter distributions in North Carolina
NASA Astrophysics Data System (ADS)
Christakos, George; Serre, Marc L.
Spatiotemporal maps of particulate matter (PM) concentrations contribute considerably to the understanding of the underlying natural processes and the adequate assessment of the PM health effects. These maps should be derived using an approach that combines rigorous mathematical formulation with sound science. To achieve such a task, the PM 10 distribution in the state of North Carolina is studied using the Bayesian maximum entropy (BME) mapping method. This method is based on a realistic representation of the spatiotemporal domain, which can integrate rigorously and efficiently various forms of physical knowledge and sources of uncertainty. BME offers a complete characterization of PM 10 concentration patterns in terms of multi-point probability distributions and allows considerable flexibility regarding the choice of the appropriate concentration estimates. The PM 10 maps show significant variability both spatially and temporally, a finding that may be associated with geographical characteristics, climatic changes, seasonal patterns, and random fluctuations. The inherently spatiotemporal nature of PM 10 variation is demonstrated by means of theoretical considerations as well as in terms of the more accurate PM 10 predictions of composite space/time analysis compared to spatial estimation. It is shown that the study of PM 10 distributions in North Carolina can be improved by properly incorporating uncertain data into the mapping process, whereas more informative estimates are generated by considering soft data at the estimation points. Uncertainty maps illustrate the significance of stochastic PM 10 characterization in space/time, and identify limitations associated with inadequate interpolation techniques. Stochastic PM 10 analysis has important applications in the optimization of monitoring networks in space and time, environmental risk assessment, health management and administration, etc.
Clustering Analysis of Seismicity and Aftershock Identification
Zaliapin, Ilya; Gabrielov, Andrei; Keilis-Borok, Vladimir; Wong, Henry [Department of Mathematics and Statistics, University of Nevada, Reno, Nevada 89557-0084 (United States); Departments of Mathematics and Earth and Atmospheric Sciences, Purdue University, West Lafayette, Indiana 47907-1395 (United States); Institute of Geophysics and Planetary Physics, and Department of Earth and Space Sciences, University of California Los Angeles, 3845 Slichter Hall, Los Angeles, California 90095-1567 (United States)
2008-07-04
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. E 69, 066106 (2004)] based on the space-time-magnitude nearest-neighbor distance {eta} between earthquakes. We show that for a homogeneous Poisson marked point field with exponential marks, the distance {eta} 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 {eta} 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.
VUV-FEL-Statistics: "Reliability Analysis of the VUV- and the X-FEL" Goal: To analyze and optimize the reliability of the VUV-FEL and to project it to the X-FEL here: Statistical analysis of VUV-FEL-Downtimes Goal tO failurestepness b "true" Weibull-parameters: characteristic lifetime T continuous randomvariable t Weibull
Evaluation of Distribution Analysis Software for DER Applications
Staunton, RH
2003-01-23
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.
Global sensitivity analysis in wind energy assessment
NASA Astrophysics Data System (ADS)
Tsvetkova, O.; Ouarda, T. B.
2012-12-01
Wind energy is one of the most promising renewable energy sources. Nevertheless, it is not yet a common source of energy, although there is enough wind potential to supply world's energy demand. One of the most prominent obstacles on the way of employing wind energy is the uncertainty associated with wind energy assessment. Global sensitivity analysis (SA) studies how the variation of input parameters in an abstract model effects the variation of the variable of interest or the output variable. It also provides ways to calculate explicit measures of importance of input variables (first order and total effect sensitivity indices) in regard to influence on the variation of the output variable. Two methods of determining the above mentioned indices were applied and compared: the brute force method and the best practice estimation procedure In this study a methodology for conducting global SA of wind energy assessment at a planning stage is proposed. Three sampling strategies which are a part of SA procedure were compared: sampling based on Sobol' sequences (SBSS), Latin hypercube sampling (LHS) and pseudo-random sampling (PRS). A case study of Masdar City, a showcase of sustainable living in the UAE, is used to exemplify application of the proposed methodology. Sources of uncertainty in wind energy assessment are very diverse. In the case study the following were identified as uncertain input parameters: the Weibull shape parameter, the Weibull scale parameter, availability of a wind turbine, lifetime of a turbine, air density, electrical losses, blade losses, ineffective time losses. Ineffective time losses are defined as losses during the time when the actual wind speed is lower than the cut-in speed or higher than the cut-out speed. The output variable in the case study is the lifetime energy production. Most influential factors for lifetime energy production are identified with the ranking of the total effect sensitivity indices. The results of the present research show that the brute force method is best for wind assessment purpose, SBSS outperforms other sampling strategies in the majority of cases. The results indicate that the Weibull scale parameter, turbine lifetime and Weibull shape parameter are the three most influential variables in the case study setting. The following conclusions can be drawn from these results: 1) SBSS should be recommended for use in Monte Carlo experiments, 2) The brute force method should be recommended for conducting sensitivity analysis in wind resource assessment, and 3) Little variation in the Weibull scale causes significant variation in energy production. The presence of the two distribution parameters in the top three influential variables (the Weibull shape and scale) emphasizes the importance of accuracy of (a) choosing the distribution to model wind regime at a site and (b) estimating probability distribution parameters. This can be labeled as the most important conclusion of this research because it opens a field for further research, which the authors see could change the wind energy field tremendously.
A Weibull-PBPK model for assessing risk of arsenic-induced skin lesions in children.
Liao, Chung-Min; Lin, Tzu-Ling; Chen, Szu-Chieh
2008-03-25
Chronic arsenic exposure and skin lesions (keratosis and hyperpigmentation) are inextricably linked. This paper was to quantify the children skin lesions risks and to further recommend safe drinking water arsenic standard based on reported arsenic epidemiological data. We linked the Weibull dose-response function and a physiologically based pharmacokinetic (PBPK) model to estimate safe drinking water arsenic concentrations and to perform the risk characterization. We calculated odds ratios (ORs) to assess the relative magnitude of the effect of the arsenic exposure on the likelihood of the prevalence of children skin lesions by calculating proposed Weibull-based prevalence ratios of exposed to control groups associated with the age group-specific PBPK model predicted dimethylarsinite (MMA(III)) levels in urine. Positive relationships between arsenic exposures and cumulative prevalence ratios of skin lesions were found using Weibull dose-response model (r2=0.91-0.96). We reported that the safe drinking water arsenic standards were recommended to be 2.2 and 1 microg/L for male and 6 and 2.8 microg/L for female in 0-6 and 7-18 years age groups, respectively, based on hyperpigmentation with an excess risk of 10(-3) for a 75 years lifetime exposure. Risk predictions indicate that estimated ORs have 95% confidence intervals of 1.33-5.12, 1.74-19.15, and 2.81-19.27 based on mean drinking water arsenic contents of 283.19, 282.65, and 468.81 microg/L, respectively, in West Bengal, India, Bangladesh, and southwestern Taiwan. Our findings also suggest that increasing urinary monomethylarsonic acid (MMA) levels are associated with an increase in risks of arsenic-induced children skin lesions. PMID:18207220
Spatial interpolation of precipitation distributions using copulas
NASA Astrophysics Data System (ADS)
Bàrdossy, Andràs; Pegram, Geoffrey
2013-04-01
The interpolation of precipitation distributions is important for example for climatological studies, interpolation of precipitation on different time scales and extreme value analyses. Spatial interpolation requires a certain degree of spatial continuity. This is in our case measured with the help of a Cramer- von Mises type statistic. Examples of daily precipitation measured over 4 regions with the number of stations ranging from 222 to 748 in South Germany, show a high degree of spatial continuity of the distributions. As a further step, the interpolation itself can be carried out by interpolating • The parameters of fitted Gamma or Weibull (or other appropriate) distributions • The moments of the distributions with a subsequent fit of parametric distributions • The quantiles of the distributions directly The interdependence between the variables to be interpolated makes this task extremely difficult in all three of the above cases. However a straightforward analysis of the higher quantiles shows that their interdependence is extremely strong, allowing simultaneous interpolation of quantiles using copulas. Lower quantiles are less well structured, but they are subject to higher observation errors and are likely to be of less importance in hydrology. Thus the interpolation was carried out on the basis of the quantiles corresponding to greater than 1mm/day values. Topographical influence on precipitation is considered as a covariate. The applied copula is a mixed truncated-Gaussian and Gaussian copula, which reflects the asymmetrical dependence between topography and precipitation quantiles. A split sampling and a cross validation methodology are used to evaluate the quality of the interpolation.
The Distributed Program Reliability Analysis on Star Topologies
Ming-sang Chang; Deng-jyi Chen; Min-sheng Lin; Kuo-lung Ku
1998-01-01
We show that computing distributed program reliability on the star distributed computing system is NP-hard. We develop a polynomially solvable case to compute distributed program reliability when some additional file distribution is restricted on the star topology. We also propose a polynomial time algorithm for computing distributed program reliability with an approximate solution when the star topology is not satisfied
Reliability analysis of a structural ceramic combustion chamber
NASA Technical Reports Server (NTRS)
Salem, Jonathan A.; Manderscheid, Jane M.; Freedman, Marc R.; Gyekenyesi, John P.
1990-01-01
The Weibull modulus, fracture toughness and thermal properties of a silicon nitride material used to make a gas turbine combustor were experimentally measured. The location and nature of failure origins resulting from bend tests were determined with fractographic analysis. The measured Weibull parameters were used along with thermal and stress analysis to determine failure probabilities of the combustor with the CARES design code. The effect of data censoring, FEM mesh refinement, and fracture criterion were considered in the analysis.
Reliability analysis of a structural ceramic combustion chamber
NASA Technical Reports Server (NTRS)
Salem, Jonathan A.; Manderscheid, Jane M.; Freedman, Marc R.; Gyekenyesi, John P.
1991-01-01
The Weibull modulus, fracture toughness and thermal properties of a silicon nitride material used to make a gas turbine combustor were experimentally measured. The location and nature of failure origins resulting from bend tests were determined with fractographic analysis. The measured Weibull parameters were used along with thermal and stress analysis to determine failure probabilities of the combustor with the CARES design code. The effect of data censoring, FEM mesh refinement, and fracture criterion were considered in the analysis.
Order statistics from the type i generalized logistic distribution
N. Balakrishnan; M. Y. Leung
1988-01-01
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,
Phylogenetic analysis on the soil bacteria distributed in karst forest
Zhou, JunPei; Huang, Ying; Mo, MingHe
2009-01-01
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). PMID:24031430
A meta-analysis of parton distribution functions
NASA Astrophysics Data System (ADS)
Gao, Jun; Nadolsky, Pavel
2014-07-01
A "meta-analysis" is a method for comparison and combination of nonperturbative parton distribution functions (PDFs) in a nucleon obtained with heterogeneous procedures and assumptions. Each input parton distribution set is converted into a "meta-parametrization" based on a common functional form. By analyzing parameters of the meta-parametrizations from all input PDF ensembles, a combined PDF ensemble can be produced that has a smaller total number of PDF member sets than the original ensembles. The meta-parametrizations simplify the computation of the PDF uncertainty in theoretical predictions and provide an alternative to the 2010 PDF4LHC convention for combination of PDF uncertainties. As a practical example, we construct a META ensemble for computation of QCD observables at the Large Hadron Collider using the next-to-next-to-leading order PDF sets from CTEQ, MSTW, and NNPDF groups as the input. The META ensemble includes a central set that reproduces the average of LHC predictions based on the three input PDF ensembles and Hessian eigenvector sets for computing the combined PDF+? s uncertainty at a common QCD coupling strength of 0.118.
Silk Fiber Mechanics from Multiscale Force Distribution Analysis
Cetinkaya, Murat; Xiao, Senbo; Markert, Bernd; Stacklies, Wolfram; Gräter, Frauke
2011-01-01
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. PMID:21354403
Phylogenetic analysis reveals a scattered distribution of autumn colours
Archetti, Marco
2009-01-01
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. PMID:19126636
Pattern analysis and spatial distribution of neurons in culture.
Millet, Larry J; Collens, Mitchell B; Perry, George L W; Bashir, Rashid
2011-12-01
The nervous system is a complex, highly-ordered, integrated network of cells. Dispersed cultures of neurons enable investigations into intrinsic cellular functions without the complexities inherent in the intact nervous system. This culture process generates a homogeneously dispersed population that is assumed to be spatially random. Despite the vast number of studies utilizing dispersed neurons, few studies address the spatial distribution of large populations of neurons, in vitro. We used ink-jet printing and surface chemistry to define patterned areas of poly-lysine adhesion (?50 ?m spots) juxtaposed against a fluorinated-silane background. We quantitatively analysed populations of patterned neurons on printed protein spots, and unpatterned neurons. Using a microarray scanner, we acquired large images (72 mm × 22 mm) of patterns, and neurons with and without patterns. Fast Fourier transformation (FFT) image analysis was used to determine global alignment of neurons to patterns. Through point pattern analysis, we described the spatial organization of dispersed neurons with, or without, patterned substrates. Patterned neurons show spatial organization characteristics reminiscent of printed patterns, with spatial distributions representative of unpatterned neurons. Most notably, both patterned and unpatterned neurons show departure from null models of complete spatial randomness (CSR; a homogeneous Poisson process) at shorter distances with conformity to CSR occurring at longer distances. Cellular morphometrics show that when compared to their unpatterned counterparts, spot-patterned neurons exhibit a significant increase (p < 0.0001) in the mean dendritic circularity and an increase in the number of more circular neurons. Through neurite tracing, we show that dendritic processes are also highly confined to patterned areas, and that they are on average 58% shorter than dendrites of neurons without patterns. Our findings show that patterned areas change the spatial organization of the somata and dendrites of cultured neurons, and that traditional neuronal cultures deviate from CSR. PMID:22057472
Measurement and Analysis of Gamma-Ray Dose Distribution in Actual Ship
Hisao YAMAKOSHI; Kohtaro UEKI; Masaya NAKATA
1983-01-01
Gamma-ray dose distribution was measured in an actual ship to study applicability of point kernel method popularly applied to the calculation of ?-ray dose distribution in ships which have usually compartmentalized structures. Measured distribution was used to verify applicability of Monte Carlo method to the analysis of ?-ray dose distribution in the ship. Monte Carlo method was proved to be
Prediction of the Inert Strength Distribution of Si3N4 Diesel Valves
Andrews, M.J.; Breder, K.; Wereszczak, A.A.
1999-01-25
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.
NASA Astrophysics Data System (ADS)
Alves, Nelson A.; Morero, Lucas D.; Rizzi, Leandro G.
2015-06-01
Microcanonical thermostatistics analysis has become an important tool to reveal essential aspects of phase transitions in complex systems. An efficient way to estimate the microcanonical inverse temperature ?(E) and the microcanonical entropy S(E) is achieved with the statistical temperature weighted histogram analysis method (ST-WHAM). The strength of this method lies on its flexibility, as it can be used to analyse data produced by algorithms with generalised sampling weights. However, for any sampling weight, ST-WHAM requires the calculation of derivatives of energy histograms H(E) , which leads to non-trivial and tedious binning tasks for models with continuous energy spectrum such as those for biomolecular and colloidal systems. Here, we discuss two alternative methods that avoid the need for such energy binning to obtain continuous estimates for H(E) in order to evaluate ?(E) by using ST-WHAM: (i) a series expansion to estimate probability densities from the empirical cumulative distribution function (CDF), and (ii) a Bayesian approach to model this CDF. Comparison with a simple linear regression method is also carried out. The performance of these approaches is evaluated considering coarse-grained protein models for folding and peptide aggregation.
An Open Architecture for Distributed Malware Collection and Analysis
NASA Astrophysics Data System (ADS)
Cavalca, Davide; Goldoni, Emanuele
Honeynets have become an important tool for researchers and network operators. However, the lack of a unified honeynet data model has impeded their effectiveness, resulting in multiple unrelated data sources, each with its own proprietary access method and format. Moreover, the deployment and management of a honeynet is a time-consuming activity and the interpretation of collected data is far from trivial. HIVE (Honeynet Infrastructure in Virtualized Environment) is a novel highly scalable automated data collection and analysis architecture we designed. Our infrastructure is based on top of proven FLOSS (Free, Libre and Open Source) solutions, which have been extended and integrated with new tools we developed. We use virtualization to ease honeypot management and deployment, combining both high-interaction and low-interaction sensors in a common infrastructure. We also address the need for rapid comprehension and detailed data analysis by harnessing the power of a relational database system, which provides centralized storage and access to the collected data while ensuring its constant integrity. This chapter presents our malware data collection architecture, offering some insight in the structure and benefits of a distributed virtualized honeynet and its development. Finally, we present some techniques for the active monitoring of centralized botnets we integrated in HIVE, which allow us to track the menaces evolution and timely deploy effective countermeasures.
NASA Astrophysics Data System (ADS)
Zhang, Qing; Hua, Cheng; Xu, Guanghua
2014-02-01
As mechanical systems increase in complexity, it is becoming more and more common to observe multiple failure modes. The system failure can be regarded as the result of interaction and competition between different failure modes. It is therefore necessary to combine multiple failure modes when analysing the failure of an overall system. In this paper, a mixture Weibull proportional hazard model (MWPHM) is proposed to predict the failure of a mechanical system with multiple failure modes. The mixed model parameters are estimated by combining historical lifetime and monitoring data of all failure modes. In addition, the system failure probability density is obtained by proportionally mixing the failure probability density of multiple failure modes. Monitoring data are input into the MWPHM to estimate the system reliability and predict the system failure time. A simulated sample set is used to verify the ability of the MWPHM to model multiple failure modes. Finally, the MWPHM and the traditional Weibull proportional hazard model (WPHM) are applied to a high-pressure water descaling pump, which has two failure modes: sealing ring wear and thrust bearing damage. Results show that the MWPHM is greatly superior in system failure prediction to the WPHM.
The distributed program reliability analysis on star topologies
Ming-sang Chang; Deng-jyi Chen; Min-sheng Lin; Kuo-lung Ku
2000-01-01
A distributed computing system consists of processing elements, communication links, memory units, data files, and programs. These resources are interconnected via a communication network and controlled by a distributed operating system. The distributed program reliability in a distributed computing system is the probability that a program which runs on multiple processing elements and needs to retrieve data files from other
Subsystem Interaction Analysis in Power Distribution Systems of Next Generation Airlifters
Lindner, Douglas K.
1 Subsystem Interaction Analysis in Power Distribution Systems of Next Generation Airlifters Sriram of the electromechanical actuators used in the analysis. Keywords «Airplanes», «Power quality», «Control», «High frequency power distribution system of a next generation transport aircraft is addressed. Detailed analysis
Monolithic ceramic analysis using the SCARE program
NASA Technical Reports Server (NTRS)
Manderscheid, Jane M.
1988-01-01
The Structural Ceramics Analysis and Reliability Evaluation (SCARE) computer program calculates the fast fracture reliability of monolithic ceramic components. The code is a post-processor to the MSC/NASTRAN general purpose finite element program. The SCARE program automatically accepts the MSC/NASTRAN output necessary to compute reliability. This includes element stresses, temperatures, volumes, and areas. The SCARE program computes two-parameter Weibull strength distributions from input fracture data for both volume and surface flaws. The distributions can then be used to calculate the reliability of geometrically complex components subjected to multiaxial stress states. Several fracture criteria and flaw types are available for selection by the user, including out-of-plane crack extension theories. The theoretical basis for the reliability calculations was proposed by Batdorf. These models combine linear elastic fracture mechanics (LEFM) with Weibull statistics to provide a mechanistic failure criterion. Other fracture theories included in SCARE are the normal stress averaging technique and the principle of independent action. The objective of this presentation is to summarize these theories, including their limitations and advantages, and to provide a general description of the SCARE program, along with example problems.
Ching-Chih Tseng
2011-01-01
Most organizations have evaluated project performance primarily through cost and schedule performance measures, such as earned value management, for projects. However, to date, few tools in the project management literature have been proposed for enabling comparisons of the overall performance of projects. This study introduces a simple index, the critical ratio in time (CR(t)), as a measure of the overall
The Kumaraswamy Burr XII distribution: theory and practice
Patrícia F. Paranaíba; Edwin M. M. Ortega; Gauss M. Cordeiro; Marcelino A. R. de Pascoa
2012-01-01
For the first time, a five-parameter distribution, called the Kumaraswamy Burr XII (KwBXII) distribution, is defined and studied. The new distribution contains as special models some well-known distributions discussed in lifetime literature, such as the logistic, Weibull and Burr XII distributions, among several others. We obtain the complete moments, incomplete moments, generating and quantile functions, mean deviations, Bonferroni and Lorenz
A. Sewalem; G. J. Kistemaker; B. J. Van Doormaal
2005-01-01
The aim of this study was to use a Weibull propor- tionalhazards modeltoexplore theimpactof typetraits on the functional survival of Canadian Jersey and Ayr- shire cows. The data set consisted of 49,791 registered Jersey cows from 900 herds calving from 1985 to 2003. The corresponding figures for Ayrshire were 77,109 cows and 921 herds. Functional survival was defined as the
Specimen type and size effects on lithium hydride tensile strength distributions
Oakes, Jr, R E
1991-12-01
Weibull's two-parameter statistical-distribution function is used to account for the effects of specimen size and loading differences on strength distributions of lithium hydride. Three distinctly differing uniaxial specimen types (i.e., an elliptical-transition pure tensile specimen, an internally pressurized ring tensile, and two sizes of four-point-flexure specimens) are shown to provide different strength distributions as expected, because of their differing sizes and modes of loading. After separation of strengths into volumetric- and surface-initiated failure distributions, the Weibull characteristic strength parameters for the higher-strength tests associated with internal fracture initiations are shown to vary as predicted by the effective specimen volume Weibull relationship. Lower-strength results correlate with the effective area to much lesser degree, probably because of the limited number of surface-related failures and the different machining methods used to prepare the specimen. The strength distribution from the fourth specimen type, the predominantly equibiaxially stressed disk-flexure specimen, is well below that predicted by the two-parameter Weibull-derived effective volume or surface area relations. The two-parameter Weibull model cannot account for the increased failure probability associated with multiaxial stress fields. Derivations of effective volume and area relationships for those specimens for which none were found in the literature, the elliptical-transition tensile, the ring tensile, and the disk flexure (including the outer region), are also included.
CRACK GROWTH ANALYSIS OF SOLID OXIDE FUEL CELL ELECTROLYTES
S. Bandopadhyay; N. Nagabhushana
2003-10-01
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.
An analysis of confidence limit calculations used in AAPM Task Group No. 119
Knill, Cory; Snyder, Michael [Department of Radiation Oncology, Karmanos Cancer Center, Detroit, Michigan 48201 (United States); Department of Radiation Oncology, Karmanos Cancer Center, Detroit, Michigan 48201 and Wayne State University, Detroit, Michigan 48201 (United States)
2011-04-15
Purpose: The report issued by AAPM Task Group No. 119 outlined a procedure for evaluating the effectiveness of IMRT commissioning. The procedure involves measuring gamma pass-rate indices for IMRT plans of standard phantoms and determining if the results fall within a confidence limit set by assuming normally distributed data. As stated in the TG report, the assumption of normally distributed gamma pass rates is a convenient approximation for commissioning purposes, but may not accurately describe the data. Here the authors attempt to better describe gamma pass-rate data by fitting it to different distributions. The authors then calculate updated confidence limits using those distributions and compare them to those derived using TG No. 119 method. Methods: Gamma pass-rate data from 111 head and neck patients are fitted using the TG No. 119 normal distribution, a truncated normal distribution, and a Weibull distribution. Confidence limits to 95% are calculated for each and compared. A more general analysis of the expected differences between the TG No. 119 method of determining confidence limits and a more time-consuming curve fitting method is performed. Results: The TG No. 119 standard normal distribution does not fit the measured data. However, due to the small range of measured data points, the inaccuracy of the fit has only a small effect on the final value of the confidence limits. The confidence limits for the 111 patient plans are within 0.1% of each other for all distributions. The maximum expected difference in confidence limits, calculated using TG No. 119's approximation and a truncated distribution, is 1.2%. Conclusions: A three-parameter Weibull probability distribution more accurately fits the clinical gamma index pass-rate data than the normal distribution adopted by TG No. 119. However, the sensitivity of the confidence limit on distribution fit is low outside of exceptional circumstances.
ramysoft
2007-05-20
parameters of the Weibull distribution and acceleration factor using maximum likelihood method. ... for estimating the parameters of Weibull distribution parameters with known shape parameter. They. 2 ...... Data Analysis". John, Wiley and ...
ProtEx: a toolkit for the analysis of distributed real-time systems
Meylan, Yves Damien Meylan
2000-01-01
for the prototyping and schedulability analysis of distributed real-time systems. This toolkit focuses on a wider set of methodologies than the traditional RMA scheduling analysis tools. We also report on the design and implementation of ProtEx....
Accelerated Life Testing Model for a Generalized Birnbaum-Saunders Distribution
Boyer, Edmond
Accelerated Life Testing Model for a Generalized Birnbaum-Saunders Distribution Yao Cheng and E. A modeled by Birnbaum-Saunders (B-S) and Weibull distributions. Sometimes, materials with high cycle fatigue of this paper is to investigate a general Birnbaum-Saunders (GB-S) distribution which covers diverse hazard
NASA Astrophysics Data System (ADS)
Zamani, A. R.; Badri, M. A.
2015-04-01
Statistical analysis was done on simultaneous wave and wind using data recorded by discus-shape wave buoy. The area is located in the southern Caspian Sea near the Anzali Port. Recorded wave data were obtained through directional spectrum wave analysis. Recorded wind direction and wind speed were obtained through the related time series as well. For 12-month measurements (May 25 2007-2008), statistical calculations were done to specify the value of nonlinear auto-correlation of wave and wind using the probability distribution function of wave characteristics and statistical analysis in various time periods. The paper also presents and analyzes the amount of wave energy for the area mentioned on the basis of available database. Analyses showed a suitable comparison between the amounts of wave energy in different seasons. As a result, the best period for the largest amount of wave energy was known. Results showed that in the research period, the mean wave and wind auto correlation were about three hours. Among the probability distribution functions, i.e Weibull, Normal, Lognormal and Rayleigh, "Weibull" had the best consistency with experimental distribution function shown in different diagrams for each season. Results also showed that the mean wave energy in the research period was about 49.88 kW/m and the maximum density of wave energy was found in February and March, 2010.
Stochastic Analysis of Chain Based File Distribution Architectures with Heterogeneous Peers
Carra, Damiano
Stochastic Analysis of Chain Based File Distribution Architectures with Heterogeneous Peers Damiano links of peers have randomly distributed capacities. The distribu- tion architecture is a chain, where sophisticated, distribution architectures are required to maintain proper scalability. 1 Introduction The Peer-to-Peer
Frequency distribution histograms for the rapid analysis of data
NASA Technical Reports Server (NTRS)
Burke, P. V.; Bullen, B. L.; Poff, K. L.
1988-01-01
The mean and standard error are good representations for the response of a population to an experimental parameter and are frequently used for this purpose. Frequency distribution histograms show, in addition, responses of individuals in the population. Both the statistics and a visual display of the distribution of the responses can be obtained easily using a microcomputer and available programs. The type of distribution shown by the histogram may suggest different mechanisms to be tested.
Statistical analysis of the electrical breakdown time delay distributions in krypton
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
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.
DATALITE: a Distributed Architecture for Traffic Analysis via Light-weight Traffic Digest
Chao, Jonathan
DATALITE: a Distributed Architecture for Traffic Analysis via Light-weight Traffic Digest for Traffic Analysis via LIght- weight Traffic digEst, which introduces a set of new distributed algorithms digests (TD's) amongst the network nodes. A TD for N packets only requires O(loglog N) bits of memory
Poli, Riccardo
- pling distribution of the PSO. In this paper we introduce a novel method, which allows one to exactly determine all the characteristics of a PSO's sampling distribution and ex- plain how they change over any the analysis to the PSO with inertia weight, but the analysis is also valid for the PSO with constriction
Zhang, Xuesong
2009-05-15
EVALUATING AND DEVELOPING PARAMETER OPTIMIZATION AND UNCERTAINTY ANALYSIS METHODS FOR A COMPUTATIONALLY INTENSIVE DISTRIBUTED HYDROLOGICAL MODEL A Dissertation by XUESONG ZHANG Submitted to the Office of Graduate Studies... ANALYSIS METHODS FOR A COMPUTATIONALLY INTENSIVE DISTRIBUTED HYDROLOGICAL MODEL A Dissertation by XUESONG ZHANG Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree...
Koopman, Philip
Design Time Reliability Analysis of Distributed Fault Tolerance Algorithms Elizabeth Latronico Designing a distributed fault tolerance algorithm re- quires careful analysis of both fault models and diagnosis strategies. A system will fail if there are too many active faults, especially active Byzantine
Dynamics Analysis of Two Synchronous Machines Interconnected with a Distribution Network in ATP-EMTP
Fabrício A. M. Moura; José R. Camacho; Marcelo L. R. Chaves; Geraldo C. Guimarães
2009-01-01
The main task in this paper is to present a performance analysis of a distribution network in the presence of two synchronous generators in parallel, with its speed and voltage regulators modeled with TACS transient analysis of control systems, for distributed generation studies. This type of configuration is common in systems where renewable fuels are used as sugar cane bagasse
Automated Analysis of Fault-Tolerance in Distributed Scott D. Stoller (stoller@cs.sunysb.edu)
Stoller, Scott
Agency (DARPA) and Air Force Research Laboratory Air Force Material Command USAF under agreement number FAutomated Analysis of Fault-Tolerance in Distributed Systems Scott D. Stoller (stoller for automated analysis of fault-tolerance of distributed sys- tems is presented. It is based on a stream (or
REVSTAT Statistical Journal Volume 9, Number 3, November 2011, 247260
Alves, Maria Isabel Fraga
analysis, but it is suitable for those situations where hazard rate is constant. For mono- tonic hazard these are Weibull and gamma distributions. Both of these distributions have increasing/decreasing hazard rate to the Weibull distribution. Although Weibull distribution has a nice closed form for hazard and survival
Statistical analysis and modelling of small satellite reliability
NASA Astrophysics Data System (ADS)
Guo, Jian; Monas, Liora; Gill, Eberhard
2014-05-01
This paper attempts to characterize failure behaviour of small satellites through statistical analysis of actual in-orbit failures. A unique Small Satellite Anomalies Database comprising empirical failure data of 222 small satellites has been developed. A nonparametric analysis of the failure data has been implemented by means of a Kaplan-Meier estimation. An innovative modelling method, i.e. Bayesian theory in combination with Markov Chain Monte Carlo (MCMC) simulations, has been proposed to model the reliability of small satellites. An extensive parametric analysis using the Bayesian/MCMC method has been performed to fit a Weibull distribution to the data. The influence of several characteristics such as the design lifetime, mass, launch year, mission type and the type of satellite developers on the reliability has been analyzed. The results clearly show the infant mortality of small satellites. Compared with the classical maximum-likelihood estimation methods, the proposed Bayesian/MCMC method results in better fitting Weibull models and is especially suitable for reliability modelling where only very limited failures are observed.
Monotone Log-Odds Rate Distributions in Reliability Analysis
Yao Wang; Anwar M. Hossain; William J. Zimmer
2003-01-01
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
Analysis of an E cient Distributed Algorithm for Mutual Exclusion
Lavault, Christian
, or some very close tree-based data structures. They usually also provide e#30;cient (possibly fault distributed algorithm to solve the mutual exclusion problem in complete networks by using a dynamic logical tree structure as its basic distributed data structure, viz. a path reversal transformation in rooted n
Notes on structural analysis in a distributed collaboratory
GC van Rooyen; AH Olivier
Summary The worldwide growth of communication networks and associated technologies provide the basic infrastructure for new ways of executing the engineering process. Collaboration amongst team members seperated in time and location is of particular importance. Two broad themes can be recognized in research pertaining to distributed collaboration. One theme focusses on the technical and technological aspects of distributed work, while
Analysis Model for Domestic Hot Water Distribution Systems: Preprint
Maguire, J.; Krarti, M.; Fang, X.
2011-11-01
A thermal model was developed to estimate the energy losses from prototypical domestic hot water (DHW) distribution systems for homes. The developed model, using the TRNSYS simulation software, allows researchers and designers to better evaluate the performance of hot water distribution systems in homes. Modeling results were compared with past experimental study results and showed good agreement.
Distributed Functional Scalar Quantization: High-Resolution Analysis and Extensions
Vinith Misra; Vivek K. Goyal; Lav R. Varshney
2008-01-01
Communication of quantized information is frequently followed by a computation. We consider situations of distributed functional quantization: distributed quantization of (possibly correlated) sourc es followed by centralized computation of a function. Under smoothness conditions on the sources and function, asymptotically-optimal regular scalar quantizer designs ar e developed to minimize distortion of the computed function. Striking improvements over quantizers designed without
Reliability Test Plans for Exponentiated Log-Logistic Distribution
K. Rosaiah; R. R. L. Kantam; Santosh Kumar
2006-01-01
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
A comparative analysis of senescence in adult damselflies and dragonflies (Odonata)
Laird, Robert
A comparative analysis of senescence in adult damselflies and dragonflies (Odonata) T. N. SHERRATT of reliability theory (Gavrilov & Gavrilova, 2001) predict an initial near-Weibull (power) mortality function
Statistical distribution of mechanical properties for three graphite-epoxy material systems
NASA Technical Reports Server (NTRS)
Reese, C.; Sorem, J., Jr.
1981-01-01
Graphite-epoxy composites are playing an increasing role as viable alternative materials in structural applications necessitating thorough investigation into the predictability and reproducibility of their material strength properties. This investigation was concerned with tension, compression, and short beam shear coupon testing of large samples from three different material suppliers to determine their statistical strength behavior. Statistical results indicate that a two Parameter Weibull distribution model provides better overall characterization of material behavior for the graphite-epoxy systems tested than does the standard Normal distribution model that is employed for most design work. While either a Weibull or Normal distribution model provides adequate predictions for average strength values, the Weibull model provides better characterization in the lower tail region where the predictions are of maximum design interest. The two sets of the same material were found to have essentially the same material properties, and indicate that repeatability can be achieved.
Bivariate extreme value distributions
NASA Technical Reports Server (NTRS)
Elshamy, M.
1992-01-01
In certain engineering applications, such as those occurring in the analyses of ascent structural loads for the Space Transportation System (STS), some of the load variables have a lower bound of zero. Thus, the need for practical models of bivariate extreme value probability distribution functions with lower limits was identified. We discuss the Gumbel models and present practical forms of bivariate extreme probability distributions of Weibull and Frechet types with two parameters. Bivariate extreme value probability distribution functions can be expressed in terms of the marginal extremel distributions and a 'dependence' function subject to certain analytical conditions. Properties of such bivariate extreme distributions, sums and differences of paired extremals, as well as the corresponding forms of conditional distributions, are discussed. Practical estimation techniques are also given.
Numerical Analysis of a Cold Air Distribution System
Zhu, L.; Li, R.; Yuan, D.
2006-01-01
Cold air distribution systems may reduce the operating energy consumption of air-conditioned air supply system and improve the outside air volume percentages and indoor air quality. However, indoor temperature patterns and velocity field are easily...
Vibration Analysis of Rotating Machinery Using the Spectral Distribution Function
NASA Astrophysics Data System (ADS)
Davis, S. S.
1998-07-01
The spectral distribution function is used to characterize the vibration signal of rotating machinery. It is shown to be a more robust indicator than conventional power spectral density estimates, but requires only slightly more computational effort. The method is demonstrated with a model of a defective bearing. The spectral distribution function is applied to practical problems involving seeded helicopter transmission faults and the vibration signal from a ground-based vacuum compressor system.
Thermal Analysis of Antenna Structures. Part 2: Panel Temperature Distribution
NASA Technical Reports Server (NTRS)
Schonfeld, D.; Lansing, F. L.
1983-01-01
This article is the second in a series that analyzes the temperature distribution in microwave antennas. An analytical solution in a series form is obtained for the temperature distribution in a flat plate analogous to an antenna surface panel under arbitrary temperature and boundary conditions. The solution includes the effects of radiation and air convection from the plate. Good agreement is obtained between the numerical and analytical solutions.
Application of extreme learning machine for estimation of wind speed distribution
NASA Astrophysics Data System (ADS)
Shamshirband, Shahaboddin; Mohammadi, Kasra; Tong, Chong Wen; Petkovi?, Dalibor; Porcu, Emilio; Mostafaeipour, Ali; Ch, Sudheer; Sedaghat, Ahmad
2015-06-01
The knowledge of the probabilistic wind speed distribution is of particular significance in reliable evaluation of the wind energy potential and effective adoption of site specific wind turbines. Among all proposed probability density functions, the two-parameter Weibull function has been extensively endorsed and utilized to model wind speeds and express wind speed distribution in various locations. In this research work, extreme learning machine (ELM) is employed to compute the shape (k) and scale (c) factors of Weibull distribution function. The developed ELM model is trained and tested based upon two widely successful methods used to estimate k and c parameters. The efficiency and accuracy of ELM is compared against support vector machine, artificial neural network and genetic programming for estimating the same Weibull parameters. The survey results reveal that applying ELM approach is eventuated in attaining further precision for estimation of both Weibull parameters compared to other methods evaluated. Mean absolute percentage error, mean absolute bias error and root mean square error for k are 8.4600 %, 0.1783 and 0.2371, while for c are 0.2143 %, 0.0118 and 0.0192 m/s, respectively. In conclusion, it is conclusively found that application of ELM is particularly promising as an alternative method to estimate Weibull k and c factors.
Performance Analysis of Distributed Object-Oriented Applications
NASA Technical Reports Server (NTRS)
Schoeffler, James D.
1998-01-01
The purpose of this research was to evaluate the efficiency of a distributed simulation architecture which creates individual modules which are made self-scheduling through the use of a message-based communication system used for requesting input data from another module which is the source of that data. To make the architecture as general as possible, the message-based communication architecture was implemented using standard remote object architectures (Common Object Request Broker Architecture (CORBA) and/or Distributed Component Object Model (DCOM)). A series of experiments were run in which different systems are distributed in a variety of ways across multiple computers and the performance evaluated. The experiments were duplicated in each case so that the overhead due to message communication and data transmission can be separated from the time required to actually perform the computational update of a module each iteration. The software used to distribute the modules across multiple computers was developed in the first year of the current grant and was modified considerably to add a message-based communication scheme supported by the DCOM distributed object architecture. The resulting performance was analyzed using a model created during the first year of this grant which predicts the overhead due to CORBA and DCOM remote procedure calls and includes the effects of data passed to and from the remote objects. A report covering the distributed simulation software and the results of the performance experiments has been submitted separately. The above report also discusses possible future work to apply the methodology to dynamically distribute the simulation modules so as to minimize overall computation time.
Kenkre, V.M.
with continuum mechanics as in the analysis of Ref. 8 . We focus attention on the stress tensor, whichNonlocal approach to the analysis of the stress distribution in granular systems. I. Theoretical, Albuquerque, New Mexico 87185 Received 22 August 1997 A theoretical framework for the analysis of the stress
Incremental and on-demand random walk for iterative power distribution network analysis
Yiyu Shi; Wei Yao; Jinjun Xiong; Lei He
2009-01-01
Power distribution networks (PDNs) are designed and analyzed iteratively. Random walk is among the most efficient methods for PDN analysis. We develop in this paper an incre- mental and on-demand random walk to reduce iterative analysis time. During each iteration, we map the design changes as pos- itive or negative random walks for observed nodes. To update PDN analysis result,
Incremental and on-demand random walk for iterative power distribution network analysis
Yiyu Shi; Wei Yao; Jinjun Xiong; Lei He
2009-01-01
Power distribution networks (PDNs) are designed and analyzed iteratively. Random walk is among the most efficient methods for PDN analysis. We develop in this paper an incremental and on-demand random walk to reduce iterative analysis time. During each iteration, we map the design changes as positive or negative random walks for observed nodes. To update PDN analysis result, we only
Analysis of distributed control systems with shared communication and computation resources
Payam Naghshtabrizi; Joao P. Hespanha
2009-01-01
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
MIXTURE PRINCIPAL COMPONENT ANALYSIS FOR DISTRIBUTION VOLUME PARAMETRIC IMAGING IN BRAIN PET STUDIES
Liu, K. J. Ray
. For quantitative analysis of neuroreceptor PET studies, compartmental model-based approaches are the most widely of mixture Principal Compo- nent Analysis (mPCA). Distinguishing specific binding and non-specific bindingMIXTURE PRINCIPAL COMPONENT ANALYSIS FOR DISTRIBUTION VOLUME PARAMETRIC IMAGING IN BRAIN PET
Distributions of Autocorrelated First-Order Kinetic Outcomes: Illness Severity
Englehardt, James D.
2015-01-01
Many complex systems produce outcomes having recurring, power law-like distributions over wide ranges. However, the form necessarily breaks down at extremes, whereas the Weibull distribution has been demonstrated over the full observed range. Here the Weibull distribution is derived as the asymptotic distribution of generalized first-order kinetic processes, with convergence driven by autocorrelation, and entropy maximization subject to finite positive mean, of the incremental compounding rates. Process increments represent multiplicative causes. In particular, illness severities are modeled as such, occurring in proportion to products of, e.g., chronic toxicant fractions passed by organs along a pathway, or rates of interacting oncogenic mutations. The Weibull form is also argued theoretically and by simulation to be robust to the onset of saturation kinetics. The Weibull exponential parameter is shown to indicate the number and widths of the first-order compounding increments, the extent of rate autocorrelation, and the degree to which process increments are distributed exponential. In contrast with the Gaussian result in linear independent systems, the form is driven not by independence and multiplicity of process increments, but by increment autocorrelation and entropy. In some physical systems the form may be attracting, due to multiplicative evolution of outcome magnitudes towards extreme values potentially much larger and smaller than control mechanisms can contain. The Weibull distribution is demonstrated in preference to the lognormal and Pareto I for illness severities versus (a) toxicokinetic models, (b) biologically-based network models, (c) scholastic and psychological test score data for children with prenatal mercury exposure, and (d) time-to-tumor data of the ED01 study. PMID:26061263
[Transformations of parameters in the generalized Poisson distribution for test data analysis].
Ogasawara, H
1996-02-01
The generalized Poisson distribution is a distribution which approximates various forms of mixtures of Poisson distributions. The mean and variance of the generalized Poisson distribution, which are simple functions of the two parameters of the distribution, are more useful than the original parameters in test data analysis. Therefore, we adopted two types of transformations of parameters. The first model has new parameters of mean and standard deviation. The second model contains new parameters of mean and variance/mean. An example indicates that the transformed parameters are convenient to understand the properties of data. PMID:8935832
Analysis and machine mapping of the distribution of band recoveries
Cowardin, L.M.
1977-01-01
A method of calculating distance and bearing from banding site to recovery location based on the solution of a spherical triangle is presented. X and Y distances on an ordinate grid were applied to computer plotting of recoveries on a map. The advantages and disadvantages of tables of recoveries by State or degree block, axial lines, and distance of recovery from banding site for presentation and comparison of the spatial distribution of band recoveries are discussed. A special web-shaped partition formed by concentric circles about the point of banding and great circles at 30-degree intervals through the point of banding has certain advantages over other methods. Comparison of distributions by means of a X? contingency test is illustrated. The statistic V = X?/N can be used as a measure of difference between two distributions of band recoveries and its possible use is illustrated as a measure of the degree of migrational homing.
Assessing Risk of a Serious Failure Mode Based on Limited Field Data
analysis to assess the effects of different assumptions on failure-time and retirement distributions. Index, Prediction interval, Weibull. ACRONYMS cdf cumulative distribution function DFD data freeze date ML maximum T Weibull shape parameter of the failure-time distribution T Weibull scale parameter of the failure
S. E. Abu-Youssef
The recurrence relations for product moments of generalized order statisics for a class of doubly truncated distributions are derived. Doubly truncated Weibull, exponential, Rayleigh, Burr and Pareto distributions, among others, arise as special cases of this class. Recurrence relations for product moments of order statistics and record values are obtained as they are special cases of generalized order statistics.
The Probability Distribution of Land Surface Wind Speeds ADAM H. MONAHAN AND YANPING HE
He, Yanping
The Probability Distribution of Land Surface Wind Speeds ADAM H. MONAHAN AND YANPING HE School October 2010, in final form 11 January 2011) ABSTRACT The probability density function (pdf) of land are shown to be broadly consistent with the Weibull distribution, while nighttime surface wind speeds
Benefit of Distributed Generation: A Line Loss Reduction Analysis
P. Chiradeja
2005-01-01
The impending deregulated environment facing the electric utilities in the twenty first century is both a challenge and an opportunity for a variety of technologies and operating scenarios. The need to provide acceptable power quality and reliability will create a very favorable climate for the entry of distributed resources and innovative operating practices. Of all the different parts of an
Blazes: Coordination Analysis for Distributed Peter Alvaro #1
California at Irvine, University of
, which are often extremely difficult to debug. This raises signifi- cant challenges for distributed in the Twitter Storm system, and another using the Bloom declarative language. I. INTRODUCTION The first another, follow the blazes. Appalachian trail conservancy [2]. Over the past decade, the database
Symmetry analysis of reaction diffusion equation with distributed delay
NASA Astrophysics Data System (ADS)
Zhao, Zhihong; Ge, Weigao
2015-07-01
This paper study the reaction-diffusion equation with distributed delay from the Lie group theoretic point of view. We give at first the evolutionary infinitesimal vector field v and a number of group invariant solutions corresponding to v by general symmetry group theory.
Optimizing Distributed Practice: Theoretical Analysis and Practical Implications
ERIC Educational Resources Information Center
Cepeda, Nicholas J.; Coburn, Noriko; Rohrer, Doug; Wixted, John T.; Mozer, Michael C,; Pashler, Harold
2009-01-01
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,…
An Information-Theoretic Analysis of Distributed Resource Allocation
Alpcan, Tansu
in a wide variety of systems ranging from electrical power grid to communication networks [4], [13], [24) how to design optimal communication systems for distributed resource allocation? A better quantitative Dey Abstract-- Solving a resource allocation problem in a dis- tributed way requires communication
An entropic framework for the normal distribution in capability analysis
Monica E. Dumitrescu; Norma Faris Hubele
1999-01-01
The intent of setting a threshold value on Cp,Cpk or Cpm for a quality characteristic in a manufacturing process is to constrain the percentage oi nonconforming parts. One of the important assumptions to the implementation of such a threshold value is that the quality characteristic is normally distributed. The purpose of this article is to demonstrate, using an entropic framework,
ERIC Data Base; Pagination Field Frequency Distribution Analysis.
ERIC Educational Resources Information Center
Brandhorst, Wesley T.; Marra, Samuel J.; Price, Douglas S.
A definitive study of the sizes of documents in the ERIC Data Base is reported by the ERIC Processing and Reference Facility. This is a statistical and frequency distribution study encompassing every item in the file whose record contains pagination data in machine readable form. The study provides pagination data that could be used by present and…
DATA BASE DEVELOPMENT AND ANALYSIS FOR WATER DISTRIBUTION SYSTEMS
There have been a number of studies estimating the costs of repairing, replacing, or renovating the authors aging distribution networks. Although useful in general terms, characterizing a system by age and/or breaks per mile of mains is of limited use to a utility trying to manag...
ANALYSIS OF COARSELY GROUPED DATA FROM THE LOGNORMAL DISTRIBUTION
A missing information technique is applied to blood lead data that is both grouped and assumed to be lognormally distributed. These maximum likelihood techniques are extended from the simple lognormal case to obtain solutions for a general linear model case. Various models are fi...
Conflict classification and analysis of distributed firewall policies
Ehab Al-shaer; Hazem Hamed; Raouf Boutaba; Masum Hasan
2005-01-01
Firewalls are core elements in network security. However, managing firewall rules, particularly, in multifirewall enterprise networks, has become a complex and error-prone task. Firewall filtering rules have to be written, ordered, and distributed carefully in order to avoid firewall policy anomalies that might cause network vulnerability. Therefore, inserting or modifying filtering rules in any firewall requires thorough intrafirewall and interfirewall
Analysis of vegetation distribution in Interior Alaska and sensitivity to
McGuire, A. David
distribution of four major vegetation types: tundra, deciduous forest, black spruce forest and white spruce by elevation, precipitation and south to north aspect. At the second step, forest was separated into deciduous temperatures exceeded a critical limit (+2 °C). Deciduous forests expand their range the most when any two
Analysis of dynamic foot pressure distribution and ground reaction forces
NASA Astrophysics Data System (ADS)
Ong, F. R.; Wong, T. S.
2005-04-01
The purpose of this study was to assess the relationship between forces derived from in-shoe pressure distribution and GRFs during normal gait. The relationship served to demonstrate the accuracy and reliability of the in-shoe pressure sensor. The in-shoe pressure distribution from Tekscan F-Scan system outputs vertical forces and Centre of Force (COF), while the Kistler force plate gives ground reaction forces (GRFs) in terms of Fz, Fx and Fy, as well as vertical torque, Tz. The two systems were synchronized for pressure and GRFs measurements. Data was collected from four volunteers through three trials for both left and right foot under barefoot condition with the in-shoe sensor. The forces derived from pressure distribution correlated well with the vertical GRFs, and the correlation coefficient (r2) was in the range of 0.93 to 0.99. This is a result of extended calibration, which improves pressure measurement to give better accuracy and reliability. The COF from in-shoe sensor generally matched well with the force plate COP. As for the maximum vertical torque at the forefoot during toe-off, there was no relationship with the pressure distribution. However, the maximum torque was shown to give an indication of the rotational angle of the foot.
Cooperative Patrolling via Weighted Tours: Performance Analysis and Distributed Algorithms
Bullo, Francesco
control laws for the robots to converge to optimal trajectories. First, we propose a patrolling strategy that in these last works the focus is mainly on finding optimal trajectories and in scheduling the motion, weighted by the viewpoint's priority. We consider the design of both optimal trajectories and distributed
The Assessment of Prior Distributions in Bayesian Analysis
Robert L. Winkler
1967-01-01
In the Bayesian framework, quantified judgments about uncertainty are an indispensable input to methods of statistical inference and decision. Ultimately, all components of the formal mathematical models underlying inferential procedures represent quantified judgments. In this study, the focus is on just one component, the prior distribution, and on some of the problems of assessment that arise when a person tries
Metagenomic Analysis of Water Distribution System Bacterial Communities
The microbial quality of drinking water is assessed using culture-based methods that are highly selective and that tend to underestimate the densities and diversity of microbial populations inhabiting distribution systems. In order to better understand the effect of different dis...
Massive Distributed and Parallel Log Analysis For Organizational Security
Lu, Chang
demonstrates the effectiveness of our design and shows the potential of our cloud-based distributed framework explored on multi-core CPU, FPGA, and GPU, e.g., [4]. The first two authors contributed equally outsourced to the cloud [7]. We present a cloud-based framework and protocol for organizations
Analysis of Fermi Gamma-Ray Burst duration distribution
Tarnopolski, Mariusz
2015-01-01
Two classes of GRBs, short and long, have been determined without any doubts, and are usually prescribed to different physical scenarios. A third class, intermediate in $T_{90}$ durations, has been reported to be present in the datasets of BATSE, Swift, RHESSI and possibly BeppoSAX. The latest release of $>1500$ GRBs observed by Fermi gives an opportunity to further investigate the duration distribution. The aim of this paper is to investigate whether a third class is present in the $\\log T_{90}$ distribution, or is it described by a bimodal distribution. A standard $\\chi^2$ fitting of a mixture of Gaussians is applied to 25 histograms with different binnings. Different binnings give various values of the fitting parameters, as well as the shape of the fitted curve. Among five statistically significant fits none is trimodal. Locations of the Gaussian components are in agreement with previous works. However, a trimodal distribution, understood in the sense of having three separated peaks, is not found for any ...
THE EPANET PROGRAMMER'S TOOLKIT FOR ANALYSIS OF WATER DISTRIBUTION SYSTEMS
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...
NASA Astrophysics Data System (ADS)
Kovalev, I. V.; Zelenkov, P. V.; Karaseva, M. V.; Tsarev, M. Yu; Tsarev, R. Yu
2015-01-01
The paper considers the problem of the analysis of distributed computer systems reliability with client-server architecture. A distributed computer system is a set of hardware and software for implementing the following main functions: processing, storage, transmission and data protection. This paper discusses the distributed computer systems architecture "client-server". The paper presents the scheme of the distributed computer system functioning represented as a graph where vertices are the functional state of the system and arcs are transitions from one state to another depending on the prevailing conditions. In reliability analysis we consider such reliability indicators as the probability of the system transition in the stopping state and accidents, as well as the intensity of these transitions. The proposed model allows us to obtain correlations for the reliability parameters of the distributed computer system without any assumptions about the distribution laws of random variables and the elements number in the system.
ProtEx: a toolkit for the analysis of distributed real-time systems
Meylan, Yves Damien Meylan
2000-01-01
Large-scale distributed real-time systems are increasingly difficult to analyze within the Rate Monotonic Analysis (RMA) framework. This is due partly to their heterogeneity, complex interaction between components, and the variety of scheduling...
Hunter, David J.
To identify genetic loci influencing central obesity and fat distribution, we performed a meta-analysis of 16 genome-wide association studies (GWAS, N = 38,580) informative for adult waist circumference (WC) and waist–hip ...
Use of a moments method for the analysis of flux distributions in subcritical assemblies
Cheng, Hsiang-Shou
1968-01-01
A moments method has been developed for the analysis of flux distributions in subcritical neutron-multiplying assemblies. The method determines values of the asymptotic axial and radial buckling, and of the extrapolated ...
Design and analysis of distributed primitives for mobile ad hoc networks
Chen, Yu
2006-10-30
This dissertation focuses on the design and analysis of distributed primitives for mobile ad hoc networks, in which mobile hosts are free to move arbitrarily. Arbitrary mobility adds unpredictability to the topology changes ...
Analysis of Cold Air Distribution System in an Office Building by the Numerical Simulation Method
Jian, Y.; Li, D.; Xu, H.; Ma, X.
2006-01-01
ICEBO2006, Shenzhen, China HVAC Technologies for Energy Efficiency Vol.IV-2-2 Analysis of Cold Air Distribution System in an Office Building by the Numerical Simulation Method Yiwen Jian Dan Li Hongqing Xu Xiaojun Ma... of similar buildings. Key words: Cold air distribution system, Indoor Air pattern, Numerical simulation, ADPI 1 INTRODUCTION Cold air distribution system can make full of use the cold water which is directly supplied by ice storage system...
APPROXIMATE NULL DISTRIBUTION OF THE LARGEST ROOT IN MULTIVARIATE ANALYSIS1
Johnstone, Iain M.
2010-01-01
The greatest root distribution occurs everywhere in classical multivariate analysis, but even under the null hypothesis the exact distribution has required extensive tables or special purpose software. We describe a simple approximation, based on the Tracy–Widom distribution, that in many cases can be used instead of tables or software, at least for initial screening. The quality of approximation is studied, and its use illustrated in a variety of setttings. PMID:20526465
Global distribution of Case-1 waters: An analysis from SeaWiFS measurements
Lee, Zhongping
Global distribution of Case-1 waters: An analysis from SeaWiFS measurements ZhongPing Lee a been a term frequently used to characterize water type since the seventies. However, the distribution of Case-1 waters in global scale has been vague, though open ocean waters are often referred to as Case-1
Uncertainty Analysis of the Adequacy Assessment Model of a Distributed Generation System
Paris-Sud XI, Université de
1 Uncertainty Analysis of the Adequacy Assessment Model of a Distributed Generation System Yanfu Li of distributed generation (DG) systems have been particularly focused on the probabilistic modeling of random1 , Enrico Zio1,2 1 Chair on Systems Science and the Energetic challenge, European Foundation
Goddard III, William A.
Efficient Algorithm for ``On-the-Fly'' Error Analysis of Local or Distributed Serially Correlated.interscience.wiley.com). Abstract: We describe the Dynamic Distributable Decorrelation Algorithm (DDDA) which efficiently calculates algorithms of such simulations (e.g. Metropolis algorithm1 ) often involve Markov chains. The data generated
Analysis of laser induced acoustic pulse probing of charge distributions in dielectrics
Boyer, Edmond
L-171 Analysis of laser induced acoustic pulse probing of charge distributions in dielectrics C pulse method for the determination ofelectric field or charge distributions in dielectrics are analysed years, new approaches to the study of charge storage and transport phenomena in dielectrics have been
Postmortem Analysis of Neuron Distributions in the Locus Coeruleus of Alcoholics and Suicidal Victims Donna K. Pauler August 25, 1994 1 Abstract We investigate neuron distribution and morphologysuicidal alcoholics, and suicidal alcoholics. The data consist of postmortem neuron measurements, counts, and spatial
Security Analysis and Extensions of the PCB Algorithm for Distributed Key Generation
Poovendran, Radha
Security Analysis and Extensions of the PCB Algorithm for Distributed Key Generation Radha these methods is the distributed key generation method proposed by Poovendran, Corson and Baras in [PCB],which we call the PCB scheme in this paper. The PCB scheme made use of modulo arithmetic and generalized
Analysis of Brillouin-Based Distributed Fiber Sensors Using Optical Pulse Coding
Park, Namkyoo
Analysis of Brillouin-Based Distributed Fiber Sensors Using Optical Pulse Coding Prasant K. Sahu1 the use of pulse Simplex-coding in distributed temperature sensors based on spontaneous Brillouin case, avoiding the use of optical pulse amplification. The implemented sensor, based on the Landau
A Formal Analysis of Solution Quality in FA/C Distributed Sensor Interpretation Systems \\Lambda
Carver III, Norman
by a distributed FA/C system to those produced by an equivalent centralized system, based on particular agent the quality of solutions that can be produced by an FA/Cbased system relative to particular agent problemA Formal Analysis of Solution Quality in FA/C Distributed Sensor Interpretation Systems \\Lambda
Static Analysis Meets Distributed Fault-Tolerance: Enabling State-Machine Replication the synchronization is often at the virtual-machine, middleware or OS level, and the ap- plication is unaware state-machine replication for nondeterminis- tic distributed applications. The approach exploits compile
Automated Analysis of Fault-Tolerance in Distributed Systems Scott D. Stoller y
Schneider, Fred B.
-00-1-0198, Defense Advanced Research Projects Agency (DARPA) and Air Force Research Laboratory Air Force MaterialAutomated Analysis of Fault-Tolerance in Distributed Systems #3; Scott D. Stoller y Computer- sented. It is based on a stream (or data- ow) model of distributed computation. Tem- poral (ordering
Grain size, size-distribution and dislocation structure from diffraction peak profile analysis
Gubicza, Jenõ
Grain size, size-distribution and dislocation structure from diffraction peak profile analysis T of microstructures of crystalline materials in terms of crystallite size-distribution and dislocation structures. Physically based theoretical functions and their Fourier coefficients are available for both, the size
, invertebrates (crayfish, mussels, snails) and vertebrates (fish; Fig. 1; Hansen et al. in review). Our analysis. We fit a Weibull distribution to the density data for each species. The Weibull is a flexible
Fishman, Paul Harold
1978-01-01
MINERALOGICAL ANALYSIS AND URANIUM DISTRIBUTION OF THE SEDIMENTS FROM THE UPPER JACKSON FORMATION KARNES COUNTY, TEXAS A Thesis by PAUL HAROLD FISHMAN Submitted to the Graduate College of Texas A&M University in partial fulfillment... of the reouirement for the degree of MASTER OF SCIENCE December 1978 Major Subject: Geology MINERALOGICAL ANALYSIS AND URANIUM DISTRIBUTION OF THE SEDIMENTS FROM THE UPPER JACKSON FORMATION KARNES COUNTY, TEXAS A Thesis by PAUL HAROLD FISHMAN Approved...
NASA Technical Reports Server (NTRS)
Heldenfels, Richard R
1951-01-01
A numerical method is presented for the stress analysis of stiffened-shell structures of arbitrary cross section under nonuniform temperature distributions. The method is based on a previously published procedure that is extended to include temperature effects and multicell construction. The application of the method to practical problems is discussed and an illustrative analysis is presented of a two-cell box beam under the combined action of vertical loads and a nonuniform temperature distribution.
ERIC Educational Resources Information Center
Campos, Jose Alejandro Gonzalez; Moraga, Paulina Saavedra; Del Pozo, Manuel Freire
2013-01-01
This paper introduces the generalized beta (GB) model as a new modeling tool in the educational assessment area and evaluation analysis, specifically. Unlike normal model, GB model allows us to capture some real characteristics of data and it is an important tool for understanding the phenomenon of learning. This paper develops a contrast with the…
Exploring Vector Fields with Distribution-based Streamline Analysis
Lu, Kewei; Chaudhuri, Abon; Lee, Teng-Yok; Shen, Han-Wei; Wong, Pak C.
2013-02-26
Streamline-based techniques are designed based on the idea that properties of streamlines are indicative of features in the underlying field. In this paper, we show that statistical distributions of measurements along the trajectory of a streamline can be used as a robust and effective descriptor to measure the similarity between streamlines. With the distribution-based approach, we present a framework for interactive exploration of 3D vector fields with streamline query and clustering. Streamline queries allow us to rapidly identify streamlines that share similar geometric features to the target streamline. Streamline clustering allows us to group together streamlines of similar shapes. Based on users selection, different clusters with different features at different levels of detail can be visualized to highlight features in 3D flow fields. We demonstrate the utility of our framework with simulation data sets of varying nature and size.
A Distributed Datacube Analysis Service for Radio Telescopes
NASA Astrophysics Data System (ADS)
Mahadevan, V.; Rosolowsky, E.
2011-07-01
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.
Radial distribution function analysis of the structure of activated carbons
A. Burian; A. Ratuszna; J. C. Dore
1998-01-01
The structure of a series of activated carbon materials prepared from a polymer of phenol formaldehyde resin with different degree of “burn-off” from 0 to 32% and variable porosity has been studied by wide-angle neutron scattering. The intensity measurements, extended to Q values of 50Å?1 yielded the radial distribution functions with the real space resolution of about 0.12Å. The obtained
Agent-based reasoning for distributed multi-INT analysis
NASA Astrophysics Data System (ADS)
Inchiosa, Mario E.; Parker, Miles T.; Perline, Richard
2006-05-01
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.
Statistical analysis of dendritic spine distributions in rat hippocampal cultures
2013-01-01
Background Dendritic spines serve as key computational structures in brain plasticity. Much remains to be learned about their spatial and temporal distribution among neurons. Our aim in this study was to perform exploratory analyses based on the population distributions of dendritic spines with regard to their morphological characteristics and period of growth in dissociated hippocampal neurons. We fit a log-linear model to the contingency table of spine features such as spine type and distance from the soma to first determine which features were important in modeling the spines, as well as the relationships between such features. A multinomial logistic regression was then used to predict the spine types using the features suggested by the log-linear model, along with neighboring spine information. Finally, an important variant of Ripley’s K-function applicable to linear networks was used to study the spatial distribution of spines along dendrites. Results Our study indicated that in the culture system, (i) dendritic spine densities were "completely spatially random", (ii) spine type and distance from the soma were independent quantities, and most importantly, (iii) spines had a tendency to cluster with other spines of the same type. Conclusions Although these results may vary with other systems, our primary contribution is the set of statistical tools for morphological modeling of spines which can be used to assess neuronal cultures following gene manipulation such as RNAi, and to study induced pluripotent stem cells differentiated to neurons. PMID:24088199
Ainsbury, Elizabeth A; Vinnikov, Volodymyr A; Maznyk, Nataliya A; Lloyd, David C; Rothkamm, Kai
2013-07-01
The Poisson distribution is the most widely recognised and commonly used distribution for cytogenetic radiation biodosimetry. However, it is recognised that, due to the complexity of radiation exposure cases, other distributions may be more properly applied. Here, the Poisson, gamma, negative binomial, beta, Neyman type-A and Hermite distributions are compared in terms of their applicability to 'real-life' radiation exposure situations. The identification of the most appropriate statistical model in each particular exposure situation more correctly characterises data. The results show that for acute, homogeneous (whole-body) exposures, the Poisson distribution can still give a good fit to the data. For localised partial-body exposures, the Neyman type-A model was found to be the most robust. Overall, no single distribution was found to be universally appropriate. A distribution-specific method of analysis of cytogenetic data is therefore recommended. Such an approach may lead potentially to more accurate biological dose estimates. PMID:23325781
NASA Technical Reports Server (NTRS)
Schmeckpeper, K. R.
1987-01-01
The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. This report documents the independent analysis results corresponding to the Orbiter Electrical Power Distribution and Control (EPD and C) hardware. The EPD and C hardware performs the functions of distributing, sensing, and controlling 28 volt DC power and of inverting, distributing, sensing, and controlling 117 volt 400 Hz AC power to all Orbiter subsystems from the three fuel cells in the Electrical Power Generation (EPG) subsystem. Volume 2 continues the presentation of IOA analysis worksheets and contains the potential critical items list.
CARES/LIFE Ceramics Analysis and Reliability Evaluation of Structures Life Prediction Program
NASA Technical Reports Server (NTRS)
Nemeth, Noel N.; Powers, Lynn M.; Janosik, Lesley A.; Gyekenyesi, John P.
2003-01-01
This manual describes the Ceramics Analysis and Reliability Evaluation of Structures Life Prediction (CARES/LIFE) computer program. The program calculates the time-dependent reliability of monolithic ceramic components subjected to thermomechanical and/or proof test loading. CARES/LIFE is an extension of the CARES (Ceramic Analysis and Reliability Evaluation of Structures) computer program. The program uses results from MSC/NASTRAN, ABAQUS, and ANSYS finite element analysis programs to evaluate component reliability due to inherent surface and/or volume type flaws. CARES/LIFE accounts for the phenomenon of subcritical crack growth (SCG) by utilizing the power law, Paris law, or Walker law. The two-parameter Weibull cumulative distribution function is used to characterize the variation in component strength. The effects of multiaxial stresses are modeled by using either the principle of independent action (PIA), the Weibull normal stress averaging method (NSA), or the Batdorf theory. Inert strength and fatigue parameters are estimated from rupture strength data of naturally flawed specimens loaded in static, dynamic, or cyclic fatigue. The probabilistic time-dependent theories used in CARES/LIFE, along with the input and output for CARES/LIFE, are described. Example problems to demonstrate various features of the program are also included.
Shortening Burn-In Test: Application of HVST and Weibull Statistical Analysis
Melanie Po-Leen Ooi; Zainal Abu Kassim; Serge N. Demidenko
2007-01-01
Testing plays an important role in controlling and ensuring required quality and reliability of manufactured integrated circuits (ICs) before supplying them to final users. Several types of testing are performed at different stages of the IC manufacturing process. One of them is the so-called burn-in testing (i.e., accelerated testing performed under elevated temperature and other stress conditions). Burn-in aims to
Peel testing of bond between PDMS prosthetic elastomers and cpTi: A Weibull analysis approach
Gregory Polyzois; Panagiotis Lagouvardos; Spiros Zinelis; Mary Frangou
2010-01-01
The purpose of this study was to investigate the bond strength of four silicone (PDMS) prosthetic elastomers, i.e. VST-50, A-588, TechSil 25 and Silbione used in the construction of facial prostheses to cpTi and acrylic resin as control through a primer and bonding enhancer application. A peel bond test at 90° was conducted according to ISO 813: 97 and the
Reducing Burn-in Time through High-Voltage Stress Test and Weibull Statistical Analysis
Mohd Fairuz Zakaria; Zainal Abu Kassim; Melanie Po-leen Ooi; Serge N. Demidenko
2006-01-01
To guarantee an industry standard of reliability in ICs, manufacturers incorporate special testing techniques into the circuit manufacturing process. For most electronic devices, the specific reliability required is quite high, often producing a lifespan of several years. Testing such devices for reliability under normal operating conditions would require a very long period of time to gather the data necessary for
Weibull analysis of flexural strength of a SiC\\/MoSi[sub 2] composite
Ting; Jyh Ming
1993-01-01
Although molybdenum disilicide (MoSi[sub 2]) exhibits excellent high temperature chemical stability and a melting point of 2,010C, its poor mechanical performance has severely limited its structural applications. As a results, effort has been made recently to strengthen MoSi[sub 2] by adding a second phase reinforcing material. The results from these studies show improved mechanical performance due to second phase addition.
Tsuyoshi Kiyan; Takeshi Ihara; Suguru Kameda; Tomohiro Furusato; Masanori Hara; Hidenori Akiyama
2011-01-01
Pulsed discharge plasma in supercritical fluids (SCFs) has attracted a great deal of attention in the field of plasma application for chemical processing. Characteristics of electrical breakdown are one of the important concerns for dielectric reli- ability of a plasma reactor with SCFs. In this paper, the pulsed breakdown voltages of quasi-uniform gaps were measured by changing the CO2 medium
Shortening Burn-In Test: Application of Weibull Statistical Analysis & HVST
M. Po-Leen Ooi; Zainal Abu Kassim; Serge Demidenko
2005-01-01
Burn-in is currently the most popular form of accelerated testing in the semiconductor industry. It subjects devices under test to accelerated temperature and voltage stresses to screen so-called 'infant mortalities' (latent failures). However, burn-in incurs high cost and turnaround time. This paper presents a methodology for burn-in test reduction based on the extended use of the high-voltage stress test (HVST)
Weibull analysis applied to the pull adhesion test and fracture of a metal-ceramic interface
R. A. Erck; F. A. Nichols; D. L. Schult
1994-01-01
Various tests have been developed to measure the mechanical bonding or adhesion 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
Elecromagnetic Relay Reliability Predictions by Designed Life Experiments and Weibull Analysis
W. Fontana
1965-01-01
The complexity of their failure mechanisms, the significant interaction effects of numerous operating parameters, and high test costs have led to many elaborate, expensive, time consuming, and often ineffective, test programs to characterize the life expectancy of specific relay designs under a variety of application conditions. This paper describes a program wherein a series of life tests of a newly
Weibull Analysis of Switching Contact Resistance in Laboratory and Commercial Circuit Breakers
C. H. Leung; E. Streicher; D. Fitzgerald
2007-01-01
Silver\\/tungsten powder metal electric contacts are used in circuit breakers because of their combination of high conductivity from silver, and high melting temperature from tungsten. In operations of the circuit breaker, switching arcs erode and oxidize the contact surface to create a high resistance layer that can lead to high temperature at the contacts. This arc erosion product is usually
Weibull Analysis Applied to the Pull Adhesion Test and Fracture of a MetalCeramic Interface
R. A. Erck; F. A. Nichols; D. L. Schult
1994-01-01
Various tests have been developed to measure the mechanical bonding or adhesion 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
Weibull statistical analysis of area effect on the breakdown strength in polymer films
Saeed UI-Haq; G. R. G. Raju
2002-01-01
The area and film thickness effects on the breakdown strength were examined for different polymer films at room temperature. Electrodes of four different diameters were used for this experimental work, which were in the range of 1\\/2 to 2 inches in diameter. Materials of various thickness used for this investigation were aramid paper (NOMEX type 410), Polyimide film (KAPTON), Mylar
Husimi distribution and phase space analysis of Dicke model quantum phase transition
E. Romera; R. del Real; M. Calixto
2014-09-19
The Husimi distribution is proposed for a phase space analysis of quantum phase transitions in the Dicke model of spin-boson interactions. We show that the inverse participation ratio and Wehrl entropy of the Husimi distribution give sharp signatures of the quantum phase transition. The analysis has been done using two frameworks: a numerical treatment and an analytical variational approximation. Additionally we have proposed a new characterization of the Dicke model quantum phase transition by means of the zeros of the Husimi distribution in the variational approach.
The distribution of first-passage times and durations in FOREX and future markets
Naoya Sazuka; Jun-Ichi Inoue; Enrico Scalas
2009-01-01
Possible distributions are discussed for intertrade durations and first-passage processes in financial markets. The view-point of renewal theory is assumed. In order to represent market data with relatively long durations, two types of distributions are used, namely a distribution derived from the Mittag–Leffler survival function and the Weibull distribution. For the Mittag–Leffler type distribution, the average waiting time (residual life
Long-Term Properties and Combinations of Stochastic Hull Girder Loads on Ships
Petricic, Martin
2012-01-01
of the corresponding Weibull fits, the foregoing analysis isWeibull distribution is the only one that matters in the extreme value analysis,ANALYSIS M y M y + M y whip VBM [kNm] x 10 Figure 4.14: Weibull
A data analysis expert system for large established distributed databases
NASA Technical Reports Server (NTRS)
Gnacek, Anne-Marie; An, Y. Kim; Ryan, J. Patrick
1987-01-01
A design for a natural language database interface system, called the Deductively Augmented NASA Management Decision support System (DANMDS), is presented. The DANMDS system components have been chosen on the basis of the following considerations: maximal employment of the existing NASA IBM-PC computers and supporting software; local structuring and storing of external data via the entity-relationship model; a natural easy-to-use error-free database query language; user ability to alter query language vocabulary and data analysis heuristic; and significant artificial intelligence data analysis heuristic techniques that allow the system to become progressively and automatically more useful.
Complexity analysis of pipeline mapping problems in distributed heterogeneous networks
Lin, Ying [University of Tennessee, Knoxville (UTK); Wu, Qishi [ORNL; Zhu, Mengxia [ORNL; Rao, Nageswara S [ORNL
2009-04-01
Largescale scientific applications require using various system resources to execute complex computing pipelines in distributed networks to support collaborative research. System resources are typically shared in the Internet or over dedicated connections based on their location, availability, capability, and capacity. Optimizing the network performance of computing pipelines in such distributed environments is critical to the success of these applications. We consider two types of largescale distributed applications: (1) interactive applications where a single dataset is sequentially processed along a pipeline; and (2) streaming applications where a series of datasets continuously flow through a pipeline. The computing pipelines of these applications consist of a number of modules executed in a linear order in network environments with heterogeneous resources under different constraints. Our goal is to find an efficient mapping scheme that allocates the modules of a pipeline to network nodes for minimum endtoend delay or maximum frame rate. We formulate the pipeline mappings in distributed environments as optimization problems and categorize them into six classes with different optimization goals and mapping constraints: (1) Minimum Endtoend Delay with No Node Reuse (MEDNNR), (2) Minimum Endtoend Delay with Contiguous Node Reuse (MEDCNR), (3) Minimum Endtoend Delay with Arbitrary Node Reuse (MEDANR), (4) Maximum Frame Rate with No Node Reuse or Share (MFRNNRS), (5) Maximum Frame Rate with Contiguous Node Reuse and Share (MFRCNRS), and (6) Maximum Frame Rate with Arbitrary Node Reuse and Share (MFRANRS). Here, 'contiguous node reuse' means that multiple contiguous modules along the pipeline may run on the same node and 'arbitrary node reuse' imposes no restriction on node reuse. Note that in interactive applications, a node can be reused but its resource is not shared. We prove that MEDANR is polynomially solvable and the rest are NP-complete. MEDANR, where either contiguous or noncontiguous modules in the pipeline can be mapped onto the same node, is essentially the Maximum n-hop Shortest Path problem, and can be solved using a dynamic programming method. In MEDNNR and MFRNNRS, any network node can be used only once, which requires selecting the same number of nodes for onetoone onto mapping. We show its NP-completeness by reducing from the Hamiltonian Path problem. Node reuse is allowed in MEDCNR, MFRCNRS and MFRANRS, which are similar to the Maximum n-hop Shortest Path problem that considers resource sharing. We prove their NP-completeness by reducing from the Disjoint-Connecting-Path Problem and Widest path with the Linear Capacity Constraints problem, respectively.
Probabilistic approach to identify sensitive parameter distributions in multimedia pathway analysis.
Kamboj, S.; Gnanapragasam, E.; LePoire, D.; Biwer, B. M.; Cheng, J.; Arnish, J.; Yu, C.; Chen, S. Y.; Mo, T.; Abu-Eid, R.; Thaggard, M.; Environmental Assessment; NRC
2002-01-01
Sensitive parameter distributions were identified with the use of probabilistic analysis in the RESRAD computer code. RESRAD is a multimedia pathway analysis code designed to evaluate radiological exposures resulting from radiological contamination in soil. The dose distribution was obtained by using a set of default parameter distribution/values. Most of the variations in the output dose distribution could be attributed to uncertainty in a small set of input parameters that could be considered as sensitive parameter distributions. The identification of the sensitive parameters is a first step in the prioritization of future research and information gathering. When site-specific parameter distribution/values are available for an actual site, the same process should be used with these site-specific data. Regression analysis used to identify sensitive parameters indicated that the dominant pathways depended on the radionuclide and source configurations. However, two parameter distributions were sensitive for many radionuclides: the external shielding factor when external exposure was the dominant pathway and the plant transfer factor when plant ingestion was the dominant pathway. No single correlation or regression coefficient can be used alone to identify sensitive parameters in all the cases. The coefficients are useful guides, but they have to be used in conjunction with other aids, such as scatter plots, and should undergo further analysis.
Analysis and modeling of high frequency ac power distribution systems
Zhongming Ye; Zhixiang Liang
2008-01-01
Small signal modeling of power converters is important for analysis, fast simulation and control design. The small signal modeling based on state-space averaging method has been widely used for PWM converters since the ripples are small in the inductor current or capacitor voltage. The model becomes less accurate from the real circuit if the ripple is not ignorable. In a
Distributed Principal Component Analysis for Wireless Sensor Networks
Yann-Aël Le Borgne; Sylvain Raybaud; Gianluca Bontempi
2010-01-01
The Principal Component Analysis (PCA) is a data dimensionality reduction technique 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 transform where the sensor measurements are projected on a set of principal components. When sensor measurements are correlated, a small set of
Channel flow analysis. [velocity distribution throughout blade flow field
NASA Technical Reports Server (NTRS)
Katsanis, T.
1973-01-01
The design of a proper blade profile requires calculation of the blade row flow field in order to determine the velocities on the blade surfaces. An analysis theory is presented for several methods used for this calculation and associated computer programs that were developed are discussed.
An Analysis of Currency Options and Exchange Rate Distributions
of this paper and suggest extensions of and refinements to the analysis. Keywords: BlackScholes model; currency options; foreign exchange; implied volatility; risk neutral valuation; pricing; valuation; at the money. 1 rates which is both parsimonious and more accurate than the BlackScholes model for stock behavior
Analysis of rain attenuation from experimental drop size distributions
Jose M. Garcia-Rubia; Jose M. Riera; Ana Benarroch; Pedro Garcia
2010-01-01
The prediction and analysis of rain attenuation is gaining interest in the recent years, because of the increasing use of millimetre-wave radio communication systems. In these frequencies, propagation in the troposphere produces strong degradations in the presence of rain, with deep fades for even moderate rainfall rates. More detailed measurements of the rain phenomena can be obtained with the use
Analysis of an algorithm for distributed recognition and accountability
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
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.
Haldar, Sourav; Kombrabail, Mamata; Krishnamoorthy, G; Chattopadhyay, Amitabha
2010-01-01
Due to the inherent difficulty in crystallizing membrane proteins, approaches based on fluorescence spectroscopy have proved useful in elucidating their conformational characteristics. The ion channel peptide gramicidin serves as an excellent prototype for monitoring membrane protein conformation and dynamics due to a number of reasons. We have analyzed conformational heterogeneity in membrane-bound gramicidin using fluorescence lifetime distribution analysis of tryptophan residues by the maximum entropy method (MEM). MEM represents a model-free and robust approach for analyzing fluorescence lifetime distribution. In this paper, we show for the first time, that fluorescence lifetime distribution analysis using MEM could be a convenient approach to monitor conformational heterogeneity in membrane-bound gramicidin in particular and membrane proteins in general. Lifetime distribution analysis by MEM therefore provides a novel window to monitor conformational transitions in membrane proteins. PMID:19816758
The Distribution of References Across Texts: Some Implications for Citation Analysis
Menczer, Filippo
1 The Distribution of References Across Texts: Some Implications for Citation Analysis Ying}@indiana.edu Abstract In citation network analysis, complex behavior is reduced to a simple edge, namely, node A cites the case that the contributions of all citations are treated equally, even though some citations appear
Current and future use of systems analysis in water distribution network design
I. C. Goulter
1987-01-01
Computer use in the design of water distribution networks was inititated through the use of network analysis techniques to determine system performance in terms of heads and flows. The last fifteen years, however, have seen the introduction of systems analysis optimization techniques to the range of computer models available for network design purposes. These optimization models differ markedly from the
Extracting mode components in laser intensity distribution by independent component analysis
Hefei Institute of Intelligent Machines
structure of a laser beam profile. After assembling image data of a laser spot, we propose a new analytical approach to extract laser beam mode components based on the independent component analysis tech- niqueExtracting mode components in laser intensity distribution by independent component analysis Hai
Explaining the Regional Distribution of New Economy Firms ? A Count Data Analysis
Dirk Dohse; Andrea Schertler
2003-01-01
Although there is a host of literature on the locational choice of traditional economy firms, relatively little is known about the locational needs and preferences of new economy firms. Therefore, the current paper provides an empirical analysis of the factors determining the regional distribution of new economy firms in Germany. Using a count data analysis, we find evidence that the
Xu Shengquan; Makio Takeda; Zhemin Zheng
2003-01-01
A cladistic analysis of 23 species of Sinopodisma Chang from China was undertaken based on 19 morphological characters of the adult with Tonkinacris sinensis Chang as the outgroup. The subdivision of the genus and the phylogenetic relationships were based both on the data obtained in the cladistic analysis and the distribution of species. Sinopodisma can be divided into four groups.
Analysis of vertical multijunction solar cells using a distributed circuit model
P. Shah
1975-01-01
This work describes an analysis of some of the vertical multijunction (VMJ) cell structures now being fabricated - especially the ones that combine the enhanced red response and radiation tolerance of the VMJ concept and blue response of conventional planar cells. A distributed equivalent circuit model is used for analysis of complicated junction configurations - which otherwise would be very
A network analysis of food flows within the United States of America.
Lin, Xiaowen; Dang, Qian; Konar, Megan
2014-05-20
The world food system is globalized and interconnected, in which trade plays an increasingly important role in facilitating food availability. We present a novel application of network analysis to domestic food flows within the USA, a country with global importance as a major agricultural producer and trade power. We find normal node degree distributions and Weibull node strength and betweenness centrality distributions. An unassortative network structure with high clustering coefficients exists. These network properties indicate that the USA food flow network is highly social and well-mixed. However, a power law relationship between node betweenness centrality and node degree indicates potential network vulnerability to the disturbance of key nodes. We perform an equality analysis which serves as a benchmark for global food trade, where the Gini coefficient = 0.579, Lorenz asymmetry coefficient = 0.966, and Hoover index = 0.442. These findings shed insight into trade network scaling and proxy free trade and equitable network architectures. PMID:24773310
Analysis of the tropospheric water distribution during FIRE 2
NASA Technical Reports Server (NTRS)
Westphal, Douglas L.
1993-01-01
The Penn State/NCAR mesoscale model, as adapted for use at ARC, was used as a testbed for the development and validation of cloud models for use in General Circulation Models (GCM's). This modeling approach also allows us to intercompare the predictions of the various cloud schemes within the same dynamical framework. The use of the PSU/NCAR mesoscale model also allows us to compare our results with FIRE-II (First International Satellite Cloud Climatology Project Regional Experiment) observations, instead of climate statistics. Though a promising approach, our work to date revealed several difficulties. First, the model by design is limited in spatial coverage and is only run for 12 to 48 hours at a time. Hence the quality of the simulation will depend heavily on the initial conditions. The poor quality of upper-tropospheric measurements of water vapor is well known and the situation is particularly bad for mid-latitude winter since the coupling with the surface is less direct than in summer so that relying on the model to spin-up a reasonable moisture field is not always successful. Though one of the most common atmospheric constituents, water vapor is relatively difficult to measure accurately, especially operationally over large areas. The standard NWS sondes have little sensitivity at the low temperatures where cirrus form and the data from the GOES 6.7 micron channel is difficult to quantify. For this reason, the goals of FIRE Cirrus II included characterizing the three-dimensional distribution of water vapor and clouds. In studying the data from FIRE Cirrus II, it was found that no single special observation technique provides accurate regional distributions of water vapor. The Raman lidar provides accurate measurements, but only at the Hub, for levels up to 10 km, and during nighttime hours. The CLASS sondes are more sensitive to moisture at low temperatures than are the NWS sondes, but the four stations only cover an area of two hundred kilometers on a side. The aircraft give the most accurate measurements of water vapor, but are limited in spatial and temporal coverage. This problem is partly alleviated by the use of the MAPS analyses, a four-dimensional data assimilation system that combines the previous 3-hour forecast with the available observations, but its upper-level moisture analyses are sometimes deficient because of the vapor measurement problem. An attempt was made to create a consistent four-dimensional description of the water vapor distribution during the second IFO by subjectively combining data from a variety of sources, including MAPS analyses, CLASS sondes, SPECTRE sondes, NWS sondes, GOES satellite analyses, radars, lidars, and microwave radiometers.
NASA Technical Reports Server (NTRS)
Gyekenyesi, J. P.
1986-01-01
A computer program was developed for calculating the statistical fast fracture reliability and failure probability of ceramic components. The program includes the two-parameter Weibull material fracture strength distribution model, using the principle of independent action for polyaxial stress states and Batdorf's shear-sensitive as well as shear-insensitive crack theories, all for volume distributed flaws in macroscopically isotropic solids. Both penny-shaped cracks and Griffith cracks are included in the Batdorf shear-sensitive crack response calculations, using Griffith's maximum tensile stress or critical coplanar strain energy release rate criteria to predict mixed mode fracture. Weibull material parameters can also be calculated from modulus of rupture bar tests, using the least squares method with known specimen geometry and fracture data. The reliability prediction analysis uses MSC/NASTRAN stress, temperature and volume output, obtained from the use of three-dimensional, quadratic, isoparametric, or axisymmetric finite elements. The statistical fast fracture theories employed, along with selected input and output formats and options, are summarized. An example problem to demonstrate various features of the program is included.
Object-Distribution Analysis: Technique for Parallel Loop Distribution of Object-Oriented Programs
Richard Stahl; Francky Catthoor; Diederik Verkest
2005-01-01
The next generation of embedded systems confronts the designer with multi-processor systems both for performance and energy reasons. Exploiting task-level parallelism in combination with coarse-grained loop-level parallelism is becoming crucial. The challenge is to build compiler tools for the exploration of these types of parallelism. To achieve this goal, the authors have designed a transformation framework for analysis and extraction
NASA Astrophysics Data System (ADS)
Wei, Xuefeng F.; Grill, Warren M.
2005-12-01
Deep brain stimulation (DBS) electrodes are designed to stimulate specific areas of the brain. The most widely used DBS electrode has a linear array of 4 cylindrical contacts that can be selectively turned on depending on the placement of the electrode and the specific area of the brain to be stimulated. The efficacy of DBS therapy can be improved by localizing the current delivery into specific populations of neurons and by increasing the power efficiency through a suitable choice of electrode geometrical characteristics. We investigated segmented electrode designs created by sectioning each cylindrical contact into multiple rings. Prototypes of these designs, made with different materials and larger dimensions than those of clinical DBS electrodes, were evaluated in vitro and in simulation. A finite element model was developed to study the effects of varying the electrode characteristics on the current density and field distributions in an idealized electrolytic medium and in vitro experiments were conducted to measure the electrode impedance. The current density over the electrode surface increased towards the edges of the electrode, and multiple edges increased the non-uniformity of the current density profile. The edge effects were more pronounced over the end segments than over the central segments. Segmented electrodes generated larger magnitudes of the second spatial difference of the extracellular potentials, and thus required lower stimulation intensities to achieve the same level of neuronal activation as solid electrodes. For a fixed electrode conductive area, increasing the number of segments (edges) decreased the impedance compared to a single solid electrode, because the average current density over the segments increased. Edge effects played a critical role in determining the current density distributions, neuronal excitation patterns, and impedance of cylindrical electrodes, and segmented electrodes provide a means to increase the efficiency of DBS.
Southern Arizona riparian habitat: Spatial distribution and analysis
NASA Technical Reports Server (NTRS)
Lacey, J. R.; Ogden, P. R.; Foster, K. E.
1975-01-01
The objectives of this study were centered around the demonstration of remote sensing as an inventory tool and researching the multiple uses of riparian vegetation. Specific study objectives were to: (1) map riparian vegetation along the Gila River, San Simon Creek, San Pedro River, Pantano Wash, (2) determine the feasibility of automated mapping using LANDSAT-1 computer compatible tapes, (3) locate and summarize existing mpas delineating riparian vegetation, (4) summarize data relevant to Southern Arizona's riparian products and uses, (5) document recent riparian vegetation changes along a selected portion of the San Pedro River, (6) summarize historical changes in composition and distribution of riparian vegetation, and (7) summarize sources of available photography pertinent to Southern Arizona.
Analysis of phase distribution phenomena in microgravity environments
NASA Technical Reports Server (NTRS)
Lahey, Richard, Jr.; Bonetto, Fabian
1994-01-01
In the past one of NASA's primary emphasis has been on identifying single and multiphase flow experiments which can produce new discoveries that are not possible except in a microgravity environment. While such experiments are obviously of great scientific interest, they do not necessarily provide NASA with the ability to use multiphase processes for power production and/or utilization in space. The purpose of the research presented in this paper is to demonstrate the ability of multidimensional two-fluid models for bubbly two-phase flow to accurately predict lateral phase distribution phenomena in microgravity environments. If successful, this research should provide NASA with mechanistically-based analytical methods which can be used for multiphase space design and evaluation, and should be the basis for future shuttle experiments for model verification.
Parallelization of Finite Element Analysis Codes Using Heterogeneous Distributed Computing
NASA Technical Reports Server (NTRS)
Ozguner, Fusun
1996-01-01
Performance gains in computer design are quickly consumed as users seek to analyze larger problems to a higher degree of accuracy. Innovative computational methods, such as parallel and distributed computing, seek to multiply the power of existing hardware technology to satisfy the computational demands of large applications. In the early stages of this project, experiments were performed using two large, coarse-grained applications, CSTEM and METCAN. These applications were parallelized on an Intel iPSC/860 hypercube. It was found that the overall speedup was very low, due to large, inherently sequential code segments present in the applications. The overall execution time T(sub par), of the application is dependent on these sequential segments. If these segments make up a significant fraction of the overall code, the application will have a poor speedup measure.