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1

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

NASA Astrophysics Data System (ADS)

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

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

2003-06-01

2

Analysis of the cell averaging CFAR in Weibull background using a distribution approximation  

Microsoft Academic Search

In this work, we study the performance of the cell averaging (CA) CFAR processor in the presence of uniform Weibull clutter. The major issue in this analysis is the unavailability of the distribution of the sum of independent and identically distributed (I.I.D.) Weibull random variables. We use an approximation to the distribution of the sum of i.i.d. Weibull random variables

Kashif Siddiq; Mohsin Irshad

2009-01-01

3

Using Weibull Distribution Analysis to Evaluate ALARA Performance  

SciTech Connect

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

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

2009-10-01

4

Reliability analysis of structural ceramic components using a three-parameter Weibull distribution  

NASA Technical Reports Server (NTRS)

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.

Duffy, Stephen F.; Powers, Lynn M.; Starlinger, Alois

1992-01-01

5

Reliability analysis of structural ceramic components using a three-parameter Weibull distribution  

NASA Technical Reports Server (NTRS)

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.

Duffy, Stephen F.; Powers, Lynn M.; Starlinger, Alois

1992-01-01

6

Modern estimation of the parameters of the Weibull wind speed distribution for wind energy analysis  

Microsoft Academic Search

Three methods for calculating the parameters of the Weibull wind speed distribution for wind energy analysis are presented: the maximum likelihood method, the proposed modified maximum likelihood method, and the commonly used graphical method. The application of each method is demonstrated using a sample wind speed data set, and a comparison of the accuracy of each method is also performed.

J. V. Seguro; T. W. Lambert

2000-01-01

7

On the Exponentiated Weibull Distribution  

Microsoft Academic Search

The important extension of the Weibull family—the exponentiated Weibull distribution—is reviewed with various new statistical measures. An explicit expression for the mode is derived and a comparison between the authors'and Mudholkar and Hutson's results are tabulated for various values of the parameters of the distribution. A general formula for the mean residual life function is obtained.

Manal M. Nassar; Fathy H. Eissa

2003-01-01

8

Mechanical Properties of Feed Pellets: Weibull Analysis  

Microsoft Academic Search

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

K. A. Aarseth; E. Prestløkken

2003-01-01

9

Software for Statistical Analysis of Weibull Distributions with Application to Gear Fatigue Data: User Manual with Verification  

NASA Technical Reports Server (NTRS)

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.

Kranz, Timothy L.

2002-01-01

10

Weibull Distribution From Interval Inspection Data  

NASA Technical Reports Server (NTRS)

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.

Rheinfurth, Mario H.

1987-01-01

11

Analysis of CFAR performance in Weibull clutter  

NASA Astrophysics Data System (ADS)

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

Rifkin, R.

1994-04-01

12

Independent Orbiter Assessment (IOA): Weibull analysis report  

NASA Technical Reports Server (NTRS)

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.

Raffaelli, Gary G.

1987-01-01

13

Distributed Fuzzy CFAR Detection for Weibull Clutter  

NASA Astrophysics Data System (ADS)

In Distributed detection systems, restricting the output of the local decision to one bit certainly implies a substantial information loss. In this paper, we consider the fuzzy detection, which uses a function called membership function for mapping the observation space of each local detector to a value between 0 and 1, indicating the degree of assurance about presence or absence of a signal. In this case, we examine the problem of distributed Maximum Likelihood (ML) and Order Statistic (OS) constant false alarm rate (CFAR) detections using fuzzy fusion rules such as “Algebraic Product” (AP), “Algebraic Sum” (AS), “Union” (Un) and “Intersection” (IS) in the fusion centre. For the Weibull clutter, the expression of the membership function based on the ML or OS CFAR processors in the local detectors is also obtained. For comparison, we consider a binary distributed detector, which uses the Maximum Likelihood and Algebraic Product (MLAP) or Order Statistic and Algebraic Product (OSAP) CFAR processors as the local detectors. In homogenous and non homogenous situations, multiple targets or clutter edge, the performances of the fuzzy and binary distributed detectors are analyzed and compared. The simulation results indicate the superior and robust performance of the distributed systems using fuzzy detection in the homogenous and non homogenous situations.

Zaimbashi, Amir; Taban, Mohammad Reza; Nayebi, Mohammad Mehdi

14

Program for Weibull Analysis of Fatigue Data  

NASA Technical Reports Server (NTRS)

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.

Krantz, Timothy L.

2005-01-01

15

Modified Goodness-of-Fit Tests for the Weibull Distribution.  

National Technical Information Service (NTIS)

This research will produce a new modified Anderson-Darling and W* Goodness of fit statistics for the three parameter Weibull Distribution when all parameters unknown and estimated by Maximum Likelihood-Minimum Distance combination. The critical values for...

E. Yucel

1993-01-01

16

Obtaining Physical Meaning from the Parameters in the Weibull Distribution.  

National Technical Information Service (NTIS)

The parameters (alpha, beta) of the Weibull distribution do not lend themselves to physical interpretation. This report illustrates how the mean, median, mode, and other measures may be obtained from (alpha, beta). Tables are given which display the mean,...

S. J. Bean, P. N. Somerville

1983-01-01

17

The Use of the Weibull Distribution for Thunderstorm Parameters.  

NASA Astrophysics Data System (ADS)

Most observations in thunderstorm statistics are positive, having values between 0 and . Since they are of a `duration-length' type. the normal distribution is not, in most cases, a satisfactory approximation. A widely used model is the lognormal distribution. It has the advantage of easy calculation of the distribution parameters, but, as most statistical distributions, it has the disadvantage of a nonanalytic cumulative distribution function.In the present paper, we describe how the Weibull distribution can be used to estimate some characteristics related to thunderstorms. Examples of the calculation of some further properties assuming Weibull-distributed observations are also given.From a theoretical point of view, the use of the Weibull distribution seems to be reasonable. It is a good model for describing electrical breakdown in insulating materials, and a lightning discharge is, indeed, such a breakdown.

Schütte, T.; Salka, O.; Israelsson, S.

1987-04-01

18

A wind energy analysis of Grenada: an estimation using the ‘Weibull’ density function  

Microsoft Academic Search

The Weibull density function has been used to estimate the wind energy potential in Grenada, West Indies. Based on historic recordings of mean hourly wind velocity this analysis shows the importance to incorporate the variation in wind energy potential during diurnal cycles. Wind energy assessments that are based on Weibull distribution using average daily\\/seasonal wind speeds fail to acknowledge that

D Weisser

2003-01-01

19

Bayesian estimation of life parameters in the Weibull distribution.  

NASA Technical Reports Server (NTRS)

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.

Canavos, G. C.; Tsokos, C. P.

1973-01-01

20

Statistical Analysis of Electrical Breakdown in a Micro Gap Using Weibull Distribution and Discussion on its Processes in High Voltage  

NASA Astrophysics Data System (ADS)

In this study, an experimental model is made on the basis of the Whitehead abc model and the properties of partial discharge (PD) breakdown in the micro gap are investigated. The quite unique properties of the PD breakdown in the micro gap are obtained: The voltage dependence of time to the PD breakdown and spread of residual negative charge distributions in the micro gap become discontinuous at a certain voltage amplitude. The discontinuousness in the PD breakdown properties is found to be due to the difference in surface discharge patterns in the micro gap: Polbüschel-type at lower voltage and Gleitbüschel-type at higher voltage. This paper aims at discussing the PD breakdown process at higher voltage. Time to the PD breakdown in the micro gap is analyzed using the Weibull probability distribution. The result suggests that the PD breakdown processes are classified into two different types: fatigue-failure-type and early/random-failure-type. Assuming that the PD breakdown of fatigue-failure-type is a thermally activated degradation process of Ahrenius type, the activation energy is caluculated . The value is in good accord with activation energy required for polymer bond scission caused by interaction with oxygen and ozone. The result suggests that the PD breakdown of fatigue-failure-type is caused by oxidative degradation. On the other hand, residual negative charges in the micro gap play an important role in the PD breakdown process of early/random-failure-type. In view of previous studies, it is possible that the PD breakdown process of early/random-failure-type is governed by the existing probability of structural defects where a great deal of the negative charges accumulates.

Imai, Kuniharu

21

An EOQ Model for Items with Weibull Distribution Deterioration  

Microsoft Academic Search

An inventory model is considered for deteriorating items with a variable rate of deterioration, where deterioration means decay, damage or spoilage such that the item cannot be used for its original purpose. Specifically, the Weibull distribution is used to represent the distribution of the time to deterioration. The EOQ formula is derived under conditions of constant demand, instantaneous delivery and

Richard P. Covert; George C. Philip

1973-01-01

22

Fitting Weibull distribution to ultraviolet solar radiation data  

NASA Astrophysics Data System (ADS)

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.

Ghitany, M. E.; El-Nashar, N. F.

2005-12-01

23

An informative bayesian prediction for the weibull lifetime distribution  

Microsoft Academic Search

Suppose components have lifetimes which follow a Weibull distribution with both scale and shape parameters unknown. Given the first r (r fixed) failure times of a sample of n components (type 2 censoring), predictions are to be made on the failure times of the remaining components in the sample (one sample prediction) and the lifetimes of unused components (two sample

A. M. Nigm

1989-01-01

24

Bayesian 1Sample Prediction for the 2Parameter Weibull Distribution  

Microsoft Academic Search

Given the first few failures times of a sample of components whose lifetimes follow a Weibull distribution with both scale and shape parameters unknown, a Bayesian approach is used to derive prediction bounds for the failure times of the remaining components in the sample. Iterative procedures involving considerable computation are necessary for calculating prediction bounds, but some simplification is possible

I. G. Evans; A. H. M. Nigm

1980-01-01

25

Prediction bounds using type 1 censoring for the weibull distribution  

Microsoft Academic Search

Summary. Suppose that components are put on life test and that their life times have a common Weibull distribution. Prediction bounds are derived using type 1 consored samples for unobserved sample components in the same sample and in a future sample of life times of the components. The general BATSSian approach is described. Equations are obtained from which the prediction

A. M. Nigm

1990-01-01

26

Development of a Weibull posterior distribution by combining a Weibull prior with an actual failure distribution using Bayesian inference  

NASA Technical Reports Server (NTRS)

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.

Giuntini, Michael E.; Giuntini, Ronald E.

1991-01-01

27

Weibull-type limiting distribution for replicative systems  

NASA Astrophysics Data System (ADS)

The Weibull function is widely used to describe skew distributions observed in nature. However, the origin of this ubiquity is not always obvious to explain. In the present paper, we consider the well-known Galton-Watson branching process describing simple replicative systems. The shape of the resulting distribution, about which little has been known, is found essentially indistinguishable from the Weibull form in a wide range of the branching parameter; this can be seen from the exact series expansion for the cumulative distribution, which takes a universal form. We also find that the branching process can be mapped into a process of aggregation of clusters. In the branching and aggregation process, the number of events considered for branching and aggregation grows cumulatively in time, whereas, for the binomial distribution, an independent event occurs at each time with a given success probability.

Jo, Junghyo; Fortin, Jean-Yves; Choi, M. Y.

2011-03-01

28

Investigation of Weibull statistics in fracture analysis of cast aluminum  

NASA Technical Reports Server (NTRS)

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.

Holland, F. A., Jr.; Zaretsky, E. V.

1989-01-01

29

Investigation of Weibull statistics in fracture analysis of cast aluminum  

NASA Technical Reports Server (NTRS)

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.

Holland, Frederic A., Jr.; Zaretsky, Erwin V.

1989-01-01

30

Table for estimating parameters of Weibull distribution  

NASA Technical Reports Server (NTRS)

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.

Mann, N. R.

1971-01-01

31

Kinetic Analysis of Isothermal Decomposition Process of Sodium Bicarbonate Using the Weibull Probability Function—Estimation of Density Distribution Functions of the Apparent Activation Energies  

NASA Astrophysics Data System (ADS)

The decomposition process of sodium bicarbonate (NaHCO3) has been studied by thermogravimetry in isothermal conditions at four different operating temperatures (380 K, 400 K, 420 K, and 440 K). It was found that the experimental integral and differential conversion curves at the different operating temperatures can be successfully described by the isothermal Weibull distribution function with a unique value of the shape parameter ( ? = 1.07). It was also established that the Weibull distribution parameters ( ? and ?) show independent behavior on the operating temperature. Using the integral and differential (Friedman) isoconversional methods, in the conversion (?) range of 0.20 ? ? ? 0.80, the apparent activation energy ( E a ) value was approximately constant ( E a, int = 95.2 kJmol-1 and E a, diff = 96.6 kJmol-1, respectively). The values of E a calculated by both isoconversional methods are in good agreement with the value of E a evaluated from the Arrhenius equation (94.3 kJmol-1), which was expressed through the scale distribution parameter ( ?). The Málek isothermal procedure was used for estimation of the kinetic model for the investigated decomposition process. It was found that the two-parameter Šesták-Berggren (SB) autocatalytic model best describes the NaHCO3 decomposition process with the conversion function f(?) = ?0.18(1-?)1.19. It was also concluded that the calculated density distribution functions of the apparent activation energies ( ddfE a ’s) are not dependent on the operating temperature, which exhibit the highly symmetrical behavior (shape factor = 1.00). The obtained isothermal decomposition results were compared with corresponding results of the nonisothermal decomposition process of NaHCO3.

Jankovi?, Bojan

2009-10-01

32

Lower bound on reliability for Weibull distribution when shape parameter is not estimated accurately  

NASA Technical Reports Server (NTRS)

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.

Huang, Zhaofeng; Porter, Albert A.

1990-01-01

33

Lower bound on reliability for Weibull distribution when shape parameter is not estimated accurately  

NASA Technical Reports Server (NTRS)

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.

Huang, Zhaofeng; Porter, Albert A.

1991-01-01

34

Weibull statistical analysis of area and volume effects on the breakdown strength in liquid nitrogen  

Microsoft Academic Search

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

H. Goshima; N. Hayakawa; M. Hikita; H. Okubo; K. Uchida

1995-01-01

35

A spatial scan statistic for survival data based on Weibull distribution.  

PubMed

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. Copyright © 2013 John Wiley & Sons, Ltd. PMID:24353112

Bhatt, Vijaya; Tiwari, Neeraj

2014-05-20

36

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

NASA Technical Reports Server (NTRS)

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.

Nemeth, Noel N.; Walker, Andrew; Baker, Eric H.; Murthy, Pappu L.; Bratton, Robert L.

2012-01-01

37

Comparison of Several Alternatives to Maximum Likelihood for the Weibull Distribution.  

National Technical Information Service (NTIS)

Five methods of parameter estimation for the two parameter Weibull distribution are investigated using simulation. They are: Non-Linear Regression, Log-Linearization, Weighted Least Squares, Generalized Least Squares, and Method of Moments. Effects of con...

S. J. Bean P. N. Somerville L. A. Franklin

1983-01-01

38

Evaluation of Mean Life of Power Equipment based on 3-parameter Weibull Distribution  

NASA Astrophysics Data System (ADS)

Evaluation of the mean life of equipments is a basic issue for effective equipment maintenance. This paper presents a method to estimate the mean life and its standard deviation of power system equipments with limited end-of-life failure data. We propose a model using 3-parameter Weibull distribution based on the results Li (2004) produced. It is assumed that the mean life of power equipments consists of “non end-of-life failure period” and “period of aging end-of-life failure”, which is represented by a location parameter of Weibull distribution. Three parameters of Weibull distribution are estimated by applying Levenberg-Marquardt method, which is one of the optimization algorithms. The computational procedures of non-linear regression, which take account both of good convergence and practical use, are proposed. Numerical examples show that our model better fits to actual data than 2-parameter Weibull distribution model.

Zhou, Yicheng; Kato, Moritoshi; Saitou, Naoki; Yokoyama, Ryuichi

39

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

NASA Astrophysics Data System (ADS)

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

Sazuka, Naoya; Inoue, Jun-Ichi

2007-03-01

40

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

Microsoft Academic Search

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

David M. Nanang

1998-01-01

41

Least Squares Best Fit Method for the Three Parameter Weibull Distribution: Analysis of Tensile and Bend Specimens with Volume or Surface Flaw Failure  

NASA Technical Reports Server (NTRS)

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.

Gross, Bernard

1996-01-01

42

Comparison between Weibull and gamma distributions to derive synthetic unit hydrograph using Horton ratios  

NASA Astrophysics Data System (ADS)

The two-parameter Weibull distribution (2PWD), similar to an instantaneous unit hydrograph (IUH), is parameterized in terms of Horton catchment ratios on the basis of a geomorphologic model of catchment response. For this the shape and scale parameters of the Weibull distribution are expressed analytically in terms of Horton's catchment ratios. The two parameters of the IUH derived using Nash's model, which is a two-parameter gamma distribution (2PGD), are also expressed analytically in terms of Horton ratios. The performance of the proposed methods is tested for describing a synthetic unit hydrograph (SUH) under limited data conditions. A comparison is made with the unit hydrographs derived from the event data of two real catchments, and with the existing geomorphological based 2PGD for developing SUH given by Rosso (1984). The sensitivity analysis of the 2PWD to the nondimensional parameter ? of the UH (a product of peak discharge and time to peak) shows ? to be more sensitive to the shape parameter a than the scale parameter b. Further examination to find any similarity between the behavior of 2PWD and 2PGD showed that a in 2PWD corresponds to the shape parameter n in the 2PGD, and b behaves similar to the scale parameter k in the 2PGD. Finally, practical applicability of the proposed approach to ungauged catchments is tested using field data.

Bhunya, P. K.; Berndtsson, R.; Singh, P. K.; Hubert, P.

2008-04-01

43

Predictive Failure of Cylindrical Coatings Using Weibull Analysis  

NASA Technical Reports Server (NTRS)

Rotating, coated wiping rollers used in a high-speed printing application failed primarily from fatigue. Two coating materials were evaluated: a hard, cross-linked, plasticized polyvinyl chloride (PVC) and a softer, plasticized PVC. A total of 447 tests was conducted with these coatings in a production facility. The data were evaluated using Weibull analysis. The softer coating produced more than twice the life of the harder cross-linked coating and reduced the wiper replacement rate by two-thirds, resulting in minimum production interruption.

Vlcek, Brian L.; Hendricks, Robert C.; Zaretsky, Erwin V.

2002-01-01

44

Flexural strength of fused silica: Weibull statistical analysis  

NASA Astrophysics Data System (ADS)

The development of high-energy lasers has focused attention on the need to assess the mechanical strength of optical components made of fused silica (Si02). The strength of this material is known to be highly dependent on the stressed area and the surface finish, but has not yet been properly characterized in the published literature. Recently, Detrio and collaborators at the University of Dayton Research Institute (UDRI) performed extensive ring-on-ring flexural strength measurements on fused Si02 specimens ranging in size from 1 to 9 inches in diameter and of widely differing surface quality. In this contribution, we report on a Weibull statistical analysis of the UDRI data-an analysis based on the procedure outlined in Proc. SPIE 4375, 241 (2001). We demonstrate that: (a) a two-parameter Weibull model, including the area-scaling principle, applies; (b) the shape parameter (m is asymptotically equal to 10) is essentially independent of the stressed area as well as the surface finish; (c) the characteristic strength (1-cm2 uniformly stressed area) obeys a linear law, ?C(in MPa) is asymptotically equal to 160 - 2.83x PBS®(in ppm/sr), where PBS® measures the surface/subsurface "damage." In this light, we evaluate the cumulative failure probability of optically polished and superpolished fused Si02 windows as a function of the biaxial tensile stress, for uniformly stressed areas ranging from 0.3 to 100 cm2.

Klein, Claude A.

2009-05-01

45

A new method for analysis of M-pulses CA-CFAR in Weibull background  

Microsoft Academic Search

The Weibull clutter model offers the potential to accurately represent the real clutter distribution over a much wider range of conditions than other models. Schleher introduced a method to analyze the performance of radar detection in a Weibull background, but when considering M-pulses, the joint probability density function (PDF) becomes tediously long even as the samples are independent and identically

Liu Weixian; Jeffrey S. Fu

2000-01-01

46

A two-dimensional Weibull distribution and its application to rolling  

Microsoft Academic Search

A two-dimensional Weibull distribution is presented which is obtained by transforming a two-dimensional Rayleigh distribution. The emphasis herein is on its application to describe the statistics of successive wave periods, and the results are illustrated by discussing the rolling of smaller vessels in beam seas in a simplified manner. Reference is also made to the related subjects on the joint

D. Myrhaug; E. Aa. Dahle; H. Rue

1995-01-01

47

Weibull-distributed dyke thickness reflects probabilistic character of host-rock strength  

PubMed Central

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.

Krumbholz, Michael; Hieronymus, Christoph F.; Burchardt, Steffi; Troll, Valentin R.; Tanner, David C.; Friese, Nadine

2014-01-01

48

Probabilistic Assessment of Earthquake Hazards: a Comparison among Gamma, Weibull, Generalized Exponential and Gamma Distributions  

NASA Astrophysics Data System (ADS)

Earthquake recurrence interval is one of the important ingredients towards probabilistic seismic hazard assessment (PSHA) for any location. Weibull, gamma, generalized exponential and lognormal distributions are quite established probability models in this recurrence interval estimation. Moreover these models share many important characteristics among themselves. In this paper, we aim to compare the effectiveness of these models in recurrence interval estimations and eventually in hazard analysis. To contemplate the appropriateness of these models, we use a complete and homogeneous earthquake catalogue of 20 events (M ? 7.0) spanning for the period 1846 to 1995 from North-East Himalayan region (200-320 N and 870-1000 E). The model parameters are estimated using modified maximum likelihood estimator (MMLE). No geological or geophysical evidences have been considered in this calculation. The estimated conditional probability reaches quite high after about a decade for an elapsed time of 17 years (i.e. 2012). Moreover, this study shows that the generalized exponential distribution fits the above data events more closely compared to the conventional models and hence it is tentatively concluded that generalized exponential distribution can be effectively considered in earthquake recurrence studies.

Pasari, S.

2013-05-01

49

The Use of the Weibull Distribution for Thunderstorm Parameters  

Microsoft Academic Search

Most observations in thunderstorm statistics are positive, having values between 0 and . Since they are of a `duration-length' type. the normal distribution is not, in most cases, a satisfactory approximation. A widely used model is the lognormal distribution. It has the advantage of easy calculation of the distribution parameters, but, as most statistical distributions, it has the disadvantage of

T. Schütte; O. Salka; S. Israelsson

1987-01-01

50

The Weibull–Pareto Composite Family with Applications to the Analysis of Unimodal Failure Rate Data  

Microsoft Academic Search

The Weibull distribution is composited with Pareto model to obtain a flexible, reliable long-tailed parametric distribution for modeling unimodal failure rate data. The hazard function of the composite family accommodates decreasing and unimodal failure rates, which are separated by the boundary line of the space of shape parameter, gamma, when it equals to a known constant. The least square and

Kahadawala Cooray

2009-01-01

51

Performance and cost analysis of large capacitor banks using Weibull statistics and MTBF  

NASA Astrophysics Data System (ADS)

Inertial confinement fusion projects have required increasingly larger capacitor banks. As bank size has increased, the need for high energy density capacitors has become apparent. Higher energy densities are achieved by increasing the dielectric stress while reducing life. Acceptable capacitor life is based on system mean time between failure (MTBF) for Nova, a 100 shot MTBF was deemed to be minimum. For a large population of capacitors, as in Nova, statistical analysis is required to evaluate system performance. The tradeoff between capacitor life and energy density can be characterized via Weibull statistics. A method of calculating capacitor bank reliability and capacitor bank costs based on Weibull statistics is given herein.

Merritt, B. T.; Whitham, K.

1981-06-01

52

The Effect of Mis-Specification Between the Lognormal and Weibull Distributions on the Interval Estimation of a Quantile for Complete Data  

Microsoft Academic Search

The lognormal and Weibull distributions are the most popular distributions for modeling lifetime data. In practical applications, they usually fit the data at hand well. However, their predictions may lead to large differences. The main purpose of the present article is to investigate the impacts of mis-specification between the lognormal and Weibull distributions on the interval estimation of a pth

Hong-Fwu Yu

2012-01-01

53

Estimating Weibull parameters for materials  

NASA Technical Reports Server (NTRS)

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.

Robinson, E. Y.

1971-01-01

54

Probabilistic Analysis for Comparing Fatigue Data Based on Johnson-Weibull Parameters  

NASA Technical Reports Server (NTRS)

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.

Hendricks, Robert C.; Zaretsky, Erwin V.; Vicek, Brian L.

2007-01-01

55

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

EPA Science Inventory

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

56

Weibull mixture model for isoconversional kinetic analysis of biomass oxidative pyrolysis  

NASA Astrophysics Data System (ADS)

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.

Cai, J. M.; Chen, S. Y.

2010-03-01

57

Probabilistic Analysis for Comparing Fatigue Data Based on Johnson-Weibull Parameters  

NASA Technical Reports Server (NTRS)

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

Vlcek, Brian L.; Hendricks, Robert C.; Zaretsky, Erwin V.

2013-01-01

58

The effect of surface roughness on the Weibull distribution of porcelain strength.  

PubMed

The purpose of the present study was to test the hypothesis that glazing will affect the Weibull modulus or the mean flexural strength of dental porcelain. Four groups (n = 30) of specimens were prepared from feldspathic body porcelain (Vita VMK 68). The specimens were tested in groups: original glazed condition (control), and after grinding separately with 1,000-grit, 600-grit, and 100-grit silicon carbide abrasive. A three-point flexure test was undertaken for each specimen. The flexural strength of porcelain and the Weibull modulus were then obtained using a computer program and load-to-failure data. Flexural strength decreased as surface roughness increased, and the differences were significant (p < 0.05), as determined by Tukey's multiple range test, except between the 600-grit group and the 100-grit group. The Weibull modulus of the glazed group was the largest (16.3), and the surface roughness was found to influence the Weibull modulus. PMID:20379009

Nakamura, Yoshiharu; Hojo, Satoru; Sato, Hideaki

2010-01-01

59

Application of the Weibull distribution to describe the vertical distribution of cesium-137 on a slope under permanent pasture in Luxembourg  

Microsoft Academic Search

The application of solutions of the Advection-Dispersion-Equation (ADE) for soil profiles is sometimes questionable. An alternative method, based on the Weibull distribution, has been developed, which can approximate the vertical distribution of radiocesium (137Cs) and allows extrapolation to account for the complete inventory. The structure of the equation allows simple parameters describing the soil depth profile to be derived. Reliable

H Dahm; J Niemeyer; D Schröder

2002-01-01

60

Effect of temperature on structural properties of Aloe vera ( Aloe barbadensis Miller) gel and Weibull distribution for modelling drying process  

Microsoft Academic Search

Aloe vera (Aloe barbadensis Miller) gel was dried at five inlet temperatures 50, 60, 70, 80 and 90°C, in a convective dryer with a constant air flow of 2.0±0.2m\\/s. Rehydration ratio, water holding capacity, texture, microstructure and total polysaccharide content were evaluated. Drying kinetics was estimated using the Weibull distribution (r2>0.97 and Chi-square<0.0009). Values of scale and shape parameters ranged

Margarita Miranda; Antonio Vega-Gálvez; Purificación García; Karina Di Scala; John Shi; Sophia Xue; Elsa Uribe

2010-01-01

61

Average capacity for optical wireless communication systems over exponentiated Weibull distribution non-Kolmogorov turbulent channels.  

PubMed

We model the average channel capacity of optical wireless communication systems for cases of weak to strong turbulence channels, using the exponentiation Weibull distribution model. The joint effects of the beam wander and spread, pointing errors, atmospheric attenuation, and the spectral index of non-Kolmogorov turbulence on system performance are included. Our results show that the average capacity decreases steeply as the propagation length L changes from 0 to 200 m and decreases slowly down or tends to a stable value as the propagation length L is greater than 200 m. In the weak turbulence region, by increasing the detection aperture, we can improve the average channel capacity and the atmospheric visibility as an important issue affecting the average channel capacity. In the strong turbulence region, the increase of the radius of the detection aperture cannot reduce the effects of the atmospheric turbulence on the average channel capacity, and the effect of atmospheric visibility on the channel information capacity can be ignored. The effect of the spectral power exponent on the average channel capacity in the strong turbulence region is higher than weak turbulence region. Irrespective of the details determining the turbulent channel, we can say that pointing errors have a significant effect on the average channel capacity of optical wireless communication systems in turbulence channels. PMID:24979434

Cheng, Mingjian; Zhang, Yixin; Gao, Jie; Wang, Fei; Zhao, Fengsheng

2014-06-20

62

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

NASA Astrophysics Data System (ADS)

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

Sayama, Shuji; Ishii, Seishiro; Sekine, Matsuo

63

Weibull analysis characterizes the breaking properties of dry-cured ham slices.  

PubMed

The breaking strength (?) and stress-strain relation of several muscles [biceps femoris (BF), semitendinosus (ST) and semimembranosus (SM)] and the subcutaneous fat (SF) from a Spanish dry cured ham (Protected Designation of Origin of white ham from "Teruel") have been analysed by the uniaxial tensile test in order to predict the mechanical behaviour of this meat product. Thirty pieces were analysed and the stress-strain curves were obtained. A great dispersion of the ? values was observed. This leads to the necessity of employing statistical analyses to illustrate the extent to which strength values may vary. The Weibull analysis was applied to estimate the fracture probability. SM and SF showed the highest characteristic strength. The low values of the Weibull modulus indicate that dry-cured ham tissues behave as brittle materials. The stress-strain curves present characteristic forms for BF, ST and SM, which may be associated with their composition and the extent to which they are affected by the curing process. PMID:24769143

Romero de Ávila, M Dolores; Escudero, Rosa; Ordóñez, Juan A; Isabel Cambero, M

2014-08-01

64

Effects of thermal cycling and surface roughness on the Weibull distribution of porcelain strength.  

PubMed

The objective of this study was to test the hypothesis that thermal cycling weakens the flexural strength of porcelain. Specimens of Deguceram Gold and Vita Omega 900 were tested in four groups of 30 specimens each: in the original glazed condition versus being ground with 1000-grit, 600-grit, and 100-grit silicon carbide abrasives. Corresponding to these four types of surface treatments, four groups of 30 specimens per group received 5,000 times of thermal cycling. Flexural strength was measured using a four-point flexural test, and Weibull modulus was calculated. Within each type of surface treatment, the thermal cycling treatment did not result in any decrease in flexural strength although it caused the Weibull modulus to become smaller - except for the control and thermal-cycled groups of 600-grit surface treatment. PMID:19721280

Nakamura, Yoshiharu; Hojo, Satoru; Sato, Hideaki

2009-07-01

65

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

Microsoft Academic Search

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

M Xie; T. N Goh; Y Tang

2004-01-01

66

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

PubMed Central

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

Quinn, George D.; Quinn, Janet B.

2011-01-01

67

Weibull analysis of fracture test data on bovine cortical bone: influence of orientation.  

PubMed

The fracture toughness, K IC, of a cortical bone has been experimentally determined by several researchers. The variation of K IC values occurs from the variation of specimen orientation, shape, and size during the experiment. The fracture toughness of a cortical bone is governed by the severest flaw and, hence, may be analyzed using Weibull statistics. To the best of the authors' knowledge, however, no studies of this aspect have been published. The motivation of the study is the evaluation of Weibull parameters at the circumferential-longitudinal (CL) and longitudinal-circumferential (LC) directions. We hypothesized that Weibull parameters vary depending on the bone microstructure. In the present work, a two-parameter Weibull statistical model was applied to calculate the plane-strain fracture toughness of bovine femoral cortical bone obtained using specimens extracted from CL and LC directions of the bone. It was found that the Weibull modulus of fracture toughness was larger for CL specimens compared to LC specimens, but the opposite trend was seen for the characteristic fracture toughness. The reason for these trends is the microstructural and extrinsic toughening mechanism differences between CL and LC directions bone. The Weibull parameters found in this study can be applied to develop a damage-mechanics model for bone. PMID:24385985

Khandaker, Morshed; Ekwaro-Osire, Stephen

2013-01-01

68

Anderson-Darling and Cramer-Von Mises Based Goodness-of-Fit Tests for the Weibull Distribution With Known Shape Using Normalized Spacings.  

National Technical Information Service (NTIS)

Two new goodness-of-fit tests are developed for the three-parameter Weibull distribution with known shape parameter. These procedures eliminate the need for estimating the unknown location and scale parameters prior to initiating the tests and are easily ...

E. W. Frisco

1998-01-01

69

Small Sample Acceptance Sampling Tables Using B10 Reliable Life and B10 Hazard Rate Criteria Based on the Weibull Distribution.  

National Technical Information Service (NTIS)

Acceptance criteria are established for B sub 10 reliable life and B sub 10 hazard (instantaneous failure) rate, assuming that a Weibull failure time distribution with shape parameter 0.6 = or < beta = or < 2.0 applies. B sub 10 reliable life is the time ...

D. J. Fisk

1968-01-01

70

Estimating Weibull parameters for composite materials.  

NASA Technical Reports Server (NTRS)

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.

Robinson, E. Y.

1972-01-01

71

BER Analysis of BPSK Modulation Over the Weibull Fading Channel with CCI  

Microsoft Academic Search

In this paper, we analyze the performance of binary phase shift keying (BPSK) in a Weibull fading channel in presence of cochannel interference (CCI). The performance is quantified in terms of the bit error rate (BER). Two expressions are derived for the BER in this case, the first is an exact expression based on a characteristic function (CF) approach, while

Mahmoud H. Ismail; Mustafa M. Matalgah

2006-01-01

72

New Sequential Goodness-Of-Fit-Test for the Three-Parameter Weibull Distribution with Known Shape Parameter Value Based on Skewness and Q-Statistic G.O.F. Test Statistics.  

National Technical Information Service (NTIS)

Due to its flexibility, the Weibull distribution has very wide applicability in a lot of disciplines and is very prevalent in reliability theory. Thus, a lot of statistical tests that generally have a substantial degree of computional complexity have been...

T. Memis

1999-01-01

73

Reliability growth modeling analysis of the space shuttle main engines based upon the Weibull process  

NASA Technical Reports Server (NTRS)

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.

Wheeler, J. T.

1990-01-01

74

Optimal CFAR detection in Weibull clutter  

NASA Astrophysics Data System (ADS)

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

Anastassopoulos, Vassilis; Lampropoulos, George A.

1995-01-01

75

Delay Estimation for On-Chip VLSI Interconnect using Weibull Distribution Function  

Microsoft Academic Search

In deep sub-micrometer (DSM) regime the on-chip interconnect delay is significantly more dominating than the gate delay. Several approaches have been proposed to capture the interconnect delay accurately and efficiently. By interpreting the impulse response of a linear circuit as a probability distribution function (PDF), Elmore first estimated the interconnect delay. Several other approaches like PRIMO, AWE, h-Gamma, WED, D2M

R. Kar; A. Chattaraj; A. Chandra; A. K. Mal; A. K. Bhattacharjee

2008-01-01

76

Parallel systems using the Weibull model  

NASA Astrophysics Data System (ADS)

A series system reliability is based on the minimum life time of its components. Its dual, the parallel system, is based on maximum. Here, we consider the statistical analysis of a parallel system where its components follows the Weibull parametric model. Our perspective is Bayesian. Due to the mathematical complexity, to obtain the posterior distribution we use the Metropolis-Hasting simulation method. Based on this posterior, we evaluated the evidence of the Full Bayesian Significance Test -FBST- for comparing component reliabilities. The reason for using FBST is the fact that we are testing precise hypotheses. An example illustrates the methodology.

Polpo, A.; Coque, M. A.; de B. Pereira, C. A.

2008-11-01

77

Weibull-Based Design Methodology for Rotating Aircraft Engine Structures  

NASA Technical Reports Server (NTRS)

The NASA Energy Efficient Engine (E(sup 3)-Engine) is used as the basis of a Weibull-based life and reliability analysis. Each component's life and thus the engine's life is defined by high-cycle fatigue (HCF) or low-cycle fatigue (LCF). Knowing the cumulative life distribution of each of the components making up the engine as represented by a Weibull slope is a prerequisite to predicting the life and reliability of the entire engine. As the engine Weibull slope increases, the predicted lives decrease. The predicted engine lives L(sub 5) (95 % probability of survival) of approximately 17,000 and 32,000 hr do correlate with current engine maintenance practices without and with refurbishment. respectively. The individual high pressure turbine (HPT) blade lives necessary to obtain a blade system life L(sub 0.1) (99.9 % probability of survival) of 9000 hr for Weibull slopes of 3, 6 and 9, are 47,391 and 20,652 and 15,658 hr, respectively. For a design life of the HPT disks having probable points of failure equal to or greater than 36,000 hr at a probability of survival of 99.9 %, the predicted disk system life L(sub 0.1) can vary from 9,408 to 24,911 hr.

Zaretsky, Erwin; Hendricks, Robert C.; Soditus, Sherry

2002-01-01

78

Calculation of Weibull strength parameters and Batdorf flow-density constants for volume- and surface-flaw-induced fracture in ceramics  

NASA Technical Reports Server (NTRS)

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.

Shantaram, S. Pai; Gyekenyesi, John P.

1989-01-01

79

Finite-size effects on return interval distributions for weakest-link-scaling systems  

NASA Astrophysics Data System (ADS)

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.

Hristopulos, Dionissios T.; Petrakis, Manolis P.; Kaniadakis, Giorgio

2014-05-01

80

Transformation of the bathtub failure rate data in reliability for using Weibull-model analysis  

Microsoft Academic Search

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

Govind S. Mudholkar; Kobby O. Asubonteng; Alan D. Hutson

2009-01-01

81

Transmission Overhaul and Replacement Predictions Using Weibull and Renewal Theory.  

National Technical Information Service (NTIS)

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 ...

M. Savage D. G. Lewicki

1989-01-01

82

Estimation for a Weibull accelerated life testing model  

SciTech Connect

It is sometimes reasonable to assume that the lifetime distribution of an item belongs to a certain parametric family, and that actual parameter values depend upon the testing environment of the item. In the two-parameter Weibull family setting, suppose both the shape and scale parameters are expressible as functions of the testing environment. For various models of functional dependency on environment, maximum likelihood methods are used to estimate characteristics of interest at specified environmental levels. The methodology presented handles exact, censored, and grouped data. A detailed accelerated life testing analysis of stress-rupture data for Kevlar/epoxy composites is given. 10 references, 1 figure, 2 tables.

Glaser, R.E.

1984-01-01

83

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

Microsoft Academic Search

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

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

2008-01-01

84

A Weibull characterization for tensile fracture of multicomponent brittle fibers  

NASA Technical Reports Server (NTRS)

A statistical characterization for multicomponent brittle fibers in 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.

Barrows, R. G.

1977-01-01

85

On testimating the weibull shape parameter  

Microsoft Academic Search

A well-known estimator for the shape parameter of a two-parameter Weibull distribution from a failure-censored sample involves a preliminary test of àa null hypothesis concerning the parameter. Efficiency of the resulting testimator varies with the chosen level of significance of the test. We present an alternative procedure with a higher efficiency over this for each significance level under various circumstances.

Nimai Kumar Chandra; Arijit Chaudhuri

1990-01-01

86

Tables of Coefficients for the Best Linear Estimates of Location and Scale Parameters for the Gumbel and Weibull Distributions for Sample Sizes Up to and Including n=31. Tables of Coefficients for the Cramer-Rao Lower Bound and for the Minimum Variances and the Efficiency for the Gumbel Distribution.  

National Technical Information Service (NTIS)

The coefficients, ci, di, for the order statistics in the best linear estimates of location and scale parameters for the Gumbel and Weibull distributions are presented in decimal form with ten places. Some rounding errors may exist, but there are at least...

A. Fransen

1974-01-01

87

Performance Sampling and Weibull Distributions.  

ERIC Educational Resources Information Center

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)

March, James C.; March, James G.

1981-01-01

88

Weibull crack density coefficient for polydimensional stress states  

NASA Technical Reports Server (NTRS)

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.

Gross, Bernard; Gyekenyesi, John P.

1989-01-01

89

Notched Strength Prediction of Composite Materials Using Weibull-Type Integrals for Uniaxial and Biaxial Loading.  

National Technical Information Service (NTIS)

The Weibull distribution model for brittle fracture is applied to a hole size study in uniaxial tension and to a study in biaxial tension. This application of the Weibull model uses a numerical integration of stress functions across a high-failure-risk vo...

R. C. Wetherhold

1979-01-01

90

Modeling root reinforcement using root-failure Weibull survival function  

NASA Astrophysics Data System (ADS)

Root networks contribute to slope stability through complicated interactions that include mechanical compression and tension. Due to the spatial heterogeneity of root distribution and the dynamic of root turnover, the quantification of root reinforcement on steep slope is challenging and consequently the calculation of slope stability as well. Although the considerable advances in root reinforcement modeling, some important aspect remain neglected. In this study we address in particular to the role of root strength variability on the mechanical behaviors of a root bundle. Many factors may contribute to the variability of root mechanical properties even considering a single class of diameter. This work presents a new approach for quantifying root reinforcement that considers the variability of mechanical properties of each root diameter class. Using the data of laboratory tensile tests and field pullout tests, we calibrate the parameters of the Weibull survival function to implement the variability of root strength in a numerical model for the calculation of root reinforcement (RBMw). The results show that, for both laboratory and field datasets, the parameters of the Weibull distribution may be considered constant with the exponent equal to 2 and the normalized failure displacement equal to 1. Moreover, the results show that the variability of root strength in each root diameter class has a major influence on the behavior of a root bundle with important implications when considering different approaches in slope stability calculation. Sensitivity analysis shows that the calibration of the tensile force and the elasticity of the roots are the most important equations, as well as the root distribution. The new model allows the characterization of root reinforcement in terms of maximum pullout force, stiffness, and energy. Moreover, it simplifies the implementation of root reinforcement in slope stability models. The realistic quantification of root reinforcement for tensile, shear and compression behavior allows the consideration of the stabilization effects of root networks on steep slopes and the influence that this has on the triggering of shallow landslides.

Schwarz, M.; Giadrossich, F.; Cohen, D.

2013-03-01

91

A Weibull characterization for tensile fracture of multicomponent brittle fibers  

NASA Technical Reports Server (NTRS)

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.

Barrows, R. G.

1977-01-01

92

Biparametric linear estimation of CFAR against Weibull clutter  

NASA Astrophysics Data System (ADS)

A new constant false alarm rate scheme against Weibull clutter is proposed and analyzed. The scheme estimates the detection threshold using a linear combination of a fixed number of ordered statistics drawn from a reference sample. A performance assessment is made to elicit the influence of various system and distributional parameters.

Guida, Maurizio; Longo, Maurizio; Lops, Marco

1992-01-01

93

Bayesian prediction for two-parameter weibull lifetime models  

Microsoft Academic Search

Prediction methods for the two-parameter Weibull distribution are computationally complicated. This paper shows how an approximate Bayesian method can be used to simplify the computation and presents a simpler alternative for computing prediction bounds derived classically by Lawless (1973).

I. G. Evans; A. M. Nigm

1980-01-01

94

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

Microsoft Academic Search

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

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

2010-01-01

95

WEIBULL PARAMETRELER? VE YÜZDEL?KLER? ?Ç?N GÜVEN ARALI?I TAHM?N ALGOR?TMALARI  

Microsoft Academic Search

This study concerns the use of Weibull distribution in statistical component reliability. Recently, estimation of confidence intervals and confidence lower bounds for Weibull parameters and percentiles in small samples has received increasing attention in the literature. In expensive or long experiments, it is crucial to keep the sample size to a minimum, however, the estimates become less reliable as the

Mehmet Akif DANACI; Endüstri Mühendisli?i Bölümü

2009-01-01

96

Calculation of Weibull strength parameters, Batdorf flaw density constants and related statistical quantities using PC-CARES  

NASA Technical Reports Server (NTRS)

This manual describes the operation and theory of the PC-CARES (Personal Computer-Ceramic Analysis and Reliability Evaluation of Structures) computer program for the IBM PC and compatibles running PC-DOS/MS-DOR OR IBM/MS-OS/2 (version 1.1 or higher) operating systems. The primary purpose of this code is to estimate Weibull material strength parameters, the Batdorf crack density coefficient, and other related statistical quantities. Included in the manual is the description of the calculation of shape and scale parameters of the two-parameter Weibull distribution using the least-squares analysis and maximum likelihood methods for volume- and surface-flaw-induced fracture in ceramics with complete and censored samples. The methods 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 line, as well as the techniques for calculating the Batdorf flaw-density constants are also described.

Szatmary, Steven A.; Gyekenyesi, John P.; Nemeth, Noel N.

1990-01-01

97

Parallel distributed viewshed analysis  

Microsoft Academic Search

——- ... .. 1. ABSTRACT The paper describes a number of distributed approaches to implementing a parallel vklbility a]g~rithm for Viewshed analysis. The problem can be simplified by considering a range of domain partitioning strategies for optimizing tie proc=sor worldoads. The best approaches are shown to work 22 times faster across a network of 24 processors. Such strategies allow traditional

J. Andrew Ware; David B. Kidner; Philip J. Rallings

1998-01-01

98

A novel and acurate delay and slew metrics for ramp inputs for on-chip VLSI RC interconnect using Weibull distribution function  

Microsoft Academic Search

In deep sub-micrometer (DSM) regime the on-chip interconnects delay is significantly more dominating than the gate delay. Several approaches have been proposed to capture the interconnect delay accurately and efficiently. Moments of the impulse response are widely used for interconnect delay analysis, from the explicit Elmore delay (the first moment of the impulse response) expression, to moment matching methods which

Rajib Kar; Vikas Maheshwari; Sangeeta Mondal; Ashis K. Mal; A. K. Bhattacharjee

2010-01-01

99

Suppression of Sea-Ice Clutter Observed by a Millimeter Wave Radar Using a New Log-Weibull\\/CFAR System  

Microsoft Academic Search

Sea-ice clutter was measured using a millimeter wave radar with frequency of 34.860GHz, beamwidth of 0.25° and pulse length of 30ns. To determine the sea-ice clutter amplitude statistics, we investigated the log-normal, Weibull, log-Weibull and K-distributions using the Akaike Information Criterion (AIC), which is more rigorous fit of the distribution to the data than the least-squares method. It is shown

S. Sayama; M. Sekine

2004-01-01

100

Transmission overhaul and replacement predictions using Weibull and renewel theory  

NASA Technical Reports Server (NTRS)

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.

Savage, M.; Lewicki, D. G.

1989-01-01

101

Transmission overhaul and replacement predictions using Weibull and renewal theory  

NASA Technical Reports Server (NTRS)

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.

Savage, M.; Lewicki, D. G.

1989-01-01

102

Weibull-k Revisited: "Tall" Profiles and Height Variation of Wind Statistics  

NASA Astrophysics Data System (ADS)

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-k 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.

Kelly, Mark; Troen, Ib; Jørgensen, Hans E.

2014-03-01

103

Measuring the Weibull modulus of microscope slides  

NASA Technical Reports Server (NTRS)

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.

Sorensen, Carl D.

1992-01-01

104

CA-CFAR in Weibull background  

Microsoft Academic Search

Constant False Alarm Rate (CFAR) processors are the commonly used detectors in radar to maintain control of the false alarm rate in the face of local variations in the background noise level. For this paper, the Cell-Averaging Constant False Alarm Rate (CA-CFAR) was studied and later simulated in a Weibull environment with the use of the Signal Workbench (SPW), to

Char Ming Wong; Chee Hang Chang; Weixian Liu; Jeffrey S Fu

2000-01-01

105

Shrinkage testimators for the shape parameter of weibull distributin under type ii censoring  

Microsoft Academic Search

In this paper we propose some shrinkage testimators for the shape parameter of the Weibull distribution when censored samples are available and study their properties. Comparison of the testimators with Singh and Bhatkulikar (1978) and with the usual estimator, interms of mean squared error are made. It is shown that the proposed testimators

B. N. Pandey; H. J. Malik

1989-01-01

106

On the efficiency of a testimator for the weibull shape parameter  

Microsoft Academic Search

In estimating the shape parameter of a two-parameter Weibull distribution from a failure-censored sample, a recently popular procedure is to employ a testimator which is a shrinkage estimator based on a preliminary hypothesis test for a guessed value of the parameter. Such an adaptive testimator is a linear compound of the guessed value and a statistic. A new compounding coefficient

Nimai Kumar Chandra; Arijit Chaudhuri

1990-01-01

107

The ATLAS distributed analysis system  

NASA Astrophysics Data System (ADS)

In the LHC operations era, analysis of the multi-petabyte ATLAS data sample by globally distributed physicists is a challenging task. To attain the required scale the ATLAS Computing Model was designed around the concept of Grid computing, realized in the Worldwide LHC Computing Grid (WLCG), the largest distributed computational resource existing in the sciences. The ATLAS experiment currently stores over 140 PB of data and runs about 140,000 concurrent jobs continuously at WLCG sites. During the first run of the LHC, the ATLAS Distributed Analysis (DA) service has operated stably and scaled as planned. More than 1600 users submitted jobs in 2012, with 2 million or more analysis jobs per week, peaking at about a million jobs per day. The system dynamically distributes popular data to expedite processing and maximally utilize resources. The reliability of the DA service is high and steadily improving; Grid sites are continually validated against a set of standard tests, and a dedicated team of expert shifters provides user support and communicates user problems to the sites. Both the user support techniques and the direct feedback of users have been effective in improving the success rate and user experience when utilizing the distributed computing environment. In this contribution a description of the main components, activities and achievements of ATLAS distributed analysis is given. Several future improvements being undertaken will be described.

Legger, F.; Atlas Collaboration

2014-06-01

108

Economic Design of – Control Charts Under Weibull Shock Models  

Microsoft Academic Search

In this article, a moditied version of Duncan's (1956) model for the economic design of -control charts is extended to deal with situations involving the Weibull shock model. In the traditional Duncan approach to Markovian shock models, the length of sampling intervals is kept constant. When the process-failure mechanism follows a Weibull model or some other model having an increasing

P. K. Banerjee; M. A. Rahim

1988-01-01

109

Aerospace Applications of Weibull and Monte Carlo Simulation with Importance Sampling  

NASA Technical Reports Server (NTRS)

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.

Bavuso, Salvatore J.

1998-01-01

110

A Weibull brittle material failure model for the ABAQUS computer program  

SciTech Connect

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.

Bennett, J.

1991-08-01

111

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

NASA Astrophysics Data System (ADS)

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

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

1995-11-01

112

Comparison of Weibull strength parameters from flexure and spin tests of brittle materials  

NASA Technical Reports Server (NTRS)

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.

Holland, Frederic A., Jr.; Zaretsky, Erwin V.

1991-01-01

113

Spatial and Temporal Patterns of Global Onshore Wind Speed Distribution  

SciTech Connect

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.

Zhou, Yuyu; Smith, Steven J.

2013-09-09

114

Application of public-domain statistical analysis software for evaluation and comparison of comet assay data  

Microsoft Academic Search

A novel approach for statistical analysis of comet assay data (i.e.: tail moment) is proposed, employing public-domain statistical software, the R system. The analytical strategy takes into account that the distribution of comet assay data, like the tail moment, is usually skewed and do not follow a normal distribution. Probability distributions used to model comet assay data included: the Weibull,

Pablo E. Verde; Laura A. Geracitano; Lílian L. Amado; Carlos E. Rosa; Adalto Bianchini; José M. Monserrat

2006-01-01

115

Strength Distribution in Paper.  

National Technical Information Service (NTIS)

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

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

1997-01-01

116

Moment series for moment estimators of the parameters of a Weibull density  

SciTech Connect

Taylor series for the first four moments of the coefficients of variation in sampling from a 2-parameter Weibull density are given: they are taken as far as the coefficient of n/sup -24/. From these a four moment approximating distribution is set up using summatory techniques on the series. The shape parameter is treated in a similar way, but here the moment equations are no longer explicit estimators, and terms only as far as those in n/sup -12/ are given. The validity of assessed moments and percentiles of the approximating distributions is studied. Consideration is also given to properties of the moment estimator for 1/c.

Bowman, K.O.; Shenton, L.R.

1982-01-01

117

Tensile properties of short fiber composites with fiber strength distribution  

Microsoft Academic Search

The influence of fiber rupture, fiber pull-out and fiber tensile strength distribution on the post-cracking behavior of short-randomly-distributed fiber reinforced brittle-matrix composites has been analyzed using an approach based on the Weibull weakest-link statistics. The analysis led to the development of a predicting model for the composite bridging stress-crack opening displacement (sc - d) law—a fundamental material property necessary for

M. Maalej

2001-01-01

118

Distributed Clustering Using Collective Principal Component Analysis  

Microsoft Academic Search

This paper considers distributed clustering of high dimensional heterogeneous data using a distributed Principal Component Analysis (PCA) technique called the Collective PCA. It presents the Collective PCA technique which can be used independent of the clustering application. It shows a way to integrate the Collective PCA with a given off-the-shelf clustering algorithm in order to develop a distributed clustering technique.

Hillol Kargupta; Weiyun Huang; Krishnamoorthy Sivakumar; Erik L. Johnson

2001-01-01

119

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

Microsoft Academic Search

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

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

2010-01-01

120

Amplitude-distribution analysis of acoustic emission  

Microsoft Academic Search

Amplitude distribution of acoustic-emission events generated during fracture of materials contains the potential information about the fracture mechanisms. A methodology is developed for the analysis of acousticemission burst signals. Based on this, the amplitude distributions can be characterized from the cumulative counts and events data alone. This simplifies the equipment as well as the data analysis. A model for amplitude

D. Dilipkumar; V. S. R. Gudimetla; W. E. Wood

1979-01-01

121

Weibull Statistics for Upper Ocean Currents with the Fokker-Planck Equation  

NASA Astrophysics Data System (ADS)

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.

Chu, P. C.

2012-12-01

122

Statistical analysis of bubble and crystal size distributions: Formulations and procedures  

NASA Astrophysics Data System (ADS)

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.

Proussevitch, Alexander A.; Sahagian, Dork L.; Tsentalovich, Evgeni P.

2007-07-01

123

Order Statistic and Algebraic Product CFAR Detector for Weibull Clutter  

Microsoft Academic Search

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

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

2006-01-01

124

Probabilistic Weibull behavior and mechanical properties of MEMS brittle materials  

Microsoft Academic Search

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

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

2003-01-01

125

Analysis of transient temperature distribution  

Microsoft Academic Search

This paper focuses on investigation of a numerical method for transient temperature distribution, in order to analyze one kind of malfunction of turbine nozzle guide component of a turbo-fan aeroengine. Thermal fatigue acts as the most important factor resulting in cracks at nozzle guide vanes and severe cracks produced may form failure of the component of the engine. However, transient

Hai Li; Tao Cheng; Jin Zhang

2004-01-01

126

An empirical analysis of waiting times for price changes and orders in a financial market  

NASA Astrophysics Data System (ADS)

We discuss an empirical analysis of waiting time distribution for price changes and orders in a financial market and its Weibull approximation. It is widely assumed that trades in financial markets occur independently and the waiting time distribution is exponential. However, recent empirical results [Raberto et al 2002, Scalas et al 2005 etc] of high frequency financial data show that the distribution is non-exponential. Therefore, in order to understand market behavior quantitatively and systematically, it is important to check the validity of the exponential distribution hypothesis and which non-exponential distribution is appropriate. In this talk, we analyze the waiting times of Sony bank USD/JPY rate and orders. We show that the waiting time distribution for not only price changes, but also orders, is non-exponential by using non-double auction market data. We also measure exactly how much better the Weibull distribution is as an approximation by using the Weibull paper and divergence measurements. Moreover, the estimated value of the shape parameter in Weibull distribution is similar in both price changes and orders waiting time distributions.

Sazuka, Naoya

2006-03-01

127

Reliability Evaluation of a Wind-Diesel Hybrid Power System with Battery Bank Using Discrete Wind Speed Frame Analysis  

Microsoft Academic Search

This paper discusses a new analytical approach of reliability evaluation for wind-diesel hybrid power system with battery bank for power supply in remote area. The proposed approach is developed on the basis of the discrete speed frame analysis of the Weibull wind speed distribution. By employing wind speed frame analysis, an analytical model of wind-diesel hybrid system is developed, which

X. Liu; S. Islam

2006-01-01

128

Special Distributions  

NSDL National Science Digital Library

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.

Siegrist, Kyle

2008-12-24

129

JADS Analysis Toolbox. A Tool for Analysis of Distributed Simulations.  

National Technical Information Service (NTIS)

Science Applications International Corporation (SAIC) has developed a software product for the Joint Advanced Distributed Simulation (JADS) called the JADS Analysis Toolbox that has been very helpful in the troubleshooting, analysis, and visualization of ...

D. G. Gonzalez J. Black

1999-01-01

130

Wind characterization analysis incorporating genetic algorithm: A case study in Taiwan Strait  

Microsoft Academic Search

In this paper, the genetic algorithm (GA) is originally applied to compute the Weibull parameters for wind characterization analysis, in which an objective function required in GA for searching optimization solution has been first defined as well. Wind data analyzed are observed at a wind farm in the Taiwan Strait from 2006 to 2008. To accurately describe wind speed distribution

Feng-Jiao Liu; Pai-Hsun Chen; Shyi-Shiun Kuo; De-Chuan Su; Tian-Pau Chang; Yu-Hua Yu; Tsung-Chi Lin

2011-01-01

131

A fuzzy-monte carlo simulation approach for fault tree analysis  

Microsoft Academic Search

Fault tree analysis is one of the key approaches used to analyze the reliability of critical systems. Fault trees are usually analyzed using mathematical approaches or Monte Carlo simulation (MCS). This paper presents a fuzzy-Monte Carlo simulation (FMCS) approach in which the uncertain data is generated by the MCS approach. The FMCS approach is applied to the Weibull probability distribution

Saman Aliari Zonouz; Seyed Ghassem Miremadi

2006-01-01

132

Analysis of Short Circuits for Distribution Systems  

Microsoft Academic Search

This paper presents a discussion and analysis of short circuits for low-voltage distribution systems. Many distribution systems are supplied from transformers connected in delta on the low-voltage side with the mid-tap of one secondary winding, or with one corner of the delta, connected to ground. As a result, short circuits on these systems often involve failure to ground, and an

Charles F. Dalziel

1942-01-01

133

Towards Distributed Memory Parallel Program Analysis  

SciTech Connect

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

Quinlan, D; Barany, G; Panas, T

2008-06-17

134

Shuttle Electrical Power Analysis Program (Sepap) Distribution Circuit Analysis Report.  

National Technical Information Service (NTIS)

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. (Author)

E. M. Torina

1975-01-01

135

Shuttle Electrical Power Analysis Program (SEPAP) distribution circuit analysis report  

NASA Technical Reports Server (NTRS)

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.

Torina, E. M.

1975-01-01

136

Distributed leadership as a unit of analysis  

Microsoft Academic Search

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

Peter Gronn

2002-01-01

137

Modeling particle distributions for stray light analysis  

NASA Astrophysics Data System (ADS)

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.

Fleming, John; Matheson, Bruce; Dittman, Michael G.; Grochocki, Frank; Firth, Brenda

2006-09-01

138

A common analysis framework for smart distribution networks applied to survivability analysis of distribution automation  

Microsoft Academic Search

Smart distribution networks shall improve the efficiency and reliability of power distribution by intelligently managing the available power and requested load. Such intelligent power networks pose challenges for information and communication technology (ICT). Their design requires a holistic assessment of traditional power system topology and ICT architecture. Existing analysis approaches focus on analyzing the power networks components separately. For example,

Anne Koziolek; Lucia Happe; Alberto Avritzer; Sindhu Suresh

2012-01-01

139

Exponentiated Weibull model for the irradiance probability density function of a laser beam propagating through atmospheric turbulence  

NASA Astrophysics Data System (ADS)

Many distributions have been proposed to model the probability density function of irradiance fluctuations. The most widespread models nowadays are the Lognormal (LN) and Gamma-Gamma (GG) distributions. Albeit these models comply with the actual PDF data most of the time, neither of them works in all scenarios and, depending on the conditions, one of the two have to be chosen. In this paper, a new model is presented resulting in the exponentiated Weibull (EW) distribution, along with a physical justification for the appearance of the model. Previously published data are used to compare the new model with the LN and GG distributions. Results suggest that the EW distribution is the better fit for data under all aperture averaging conditions and weak-to-strong turbulence regime.

Barrios, Ricardo; Dios, Federico

2013-02-01

140

Test Population Selection from Weibull-Based, Monte Carlo Simulations of Fatigue Life  

NASA Technical Reports Server (NTRS)

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.

Vlcek, Brian L.; Zaretsky, Erwin V.; Hendricks, Robert C.

2012-01-01

141

Test Population Selection from Weibull-Based, Monte Carlo Simulations of Fatigue Life  

NASA Technical Reports Server (NTRS)

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.

Vlcek, Brian L.; Zaretsky, Erwin V.; Hendricks, Robert C.

2008-01-01

142

Assessing a Tornado Climatology from Global Tornado Intensity Distributions  

Microsoft Academic Search

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

Bernold Feuerstein; Nikolai Dotzek; Jürgen Grieser

2005-01-01

143

Performance optimisations for distributed analysis in ALICE  

NASA Astrophysics Data System (ADS)

Performance is a critical issue in a production system accommodating hundreds of analysis users. Compared to a local session, distributed analysis is exposed to services and network latencies, remote data access and heterogeneous computing infrastructure, creating a more complex performance and efficiency optimization matrix. During the last 2 years, ALICE analysis shifted from a fast development phase to the more mature and stable code. At the same time, the frameworks and tools for deployment, monitoring and management of large productions have evolved considerably too. The ALICE Grid production system is currently used by a fair share of organized and individual user analysis, consuming up to 30% or the available resources and ranging from fully I/O-bound analysis code to CPU intensive correlations or resonances studies. While the intrinsic analysis performance is unlikely to improve by a large factor during the LHC long shutdown (LS1), the overall efficiency of the system has still to be improved by an important factor to satisfy the analysis needs. We have instrumented all analysis jobs with "sensors" collecting comprehensive monitoring information on the job running conditions and performance in order to identify bottlenecks in the data processing flow. This data are collected by the MonALISa-based ALICE Grid monitoring system and are used to steer and improve the job submission and management policy, to identify operational problems in real time and to perform automatic corrective actions. In parallel with an upgrade of our production system we are aiming for low level improvements related to data format, data management and merging of results to allow for a better performing ALICE analysis.

Betev, L.; Gheata, A.; Gheata, M.; Grigoras, C.; Hristov, P.

2014-06-01

144

Probability Distributions for Offshore Wind Speeds  

NASA Astrophysics Data System (ADS)

In planning offshore wind farms, short-term wind speeds play a central role in estimating various engineering parameters, such as power output, design load, fatigue load, etc. Lacking wind speed data at a specific site, the probability distribution of wind speed serves as the primary substitute for such measurements during parameter estimation. It is common practice to model wind speeds with the Weibull distribution, but recent literature suggests that many other distributions may perform better. Such studies are often limited in either the time-span or geographic scope of their datasets. Using 10-minute average wind speed time series ranging from 1 month to 20 years in duration collected from 178 buoys around North America, we show that the widely-accepted Weibull distribution provides a poor fit to the distribution of wind speeds when compared with other models. For example several other distributions, including the bimodal Weibull, Kappa and Wakeby models, fit the data remarkably well, yielding values significantly closer to 1 than the Weibull and many other distributions. Additionally, we show that the Kappa and Wakeby predict average wind turbine power output better than other distributions, including the bimodal Weibull. Our results show that more complicated models than the two-parameter Weibull are needed to capture the complex behavior of wind, and that using such models leads to improved engineering decisions.

Morgan, E. C.; Lackner, M.; Vogel, R. M.; Baise, L. G.

2009-12-01

145

Statistical distribution of natural fractures and the possible physical generating mechanism  

Microsoft Academic Search

We have fitted field measurements of fracture spacings (from the vicinity of Lake Strom Thurmond, Georgia, U.S.A.) to the Weibull, Schuhmann and fractal distributions. The fracture spacings follow a fractal and Weibull distribution which implies that they were formed as a result of a repetitive fragmentation process. The limited variation of the fracture density with orientation in the study area

F. K. Boadu; L. T. Long

1994-01-01

146

Global analysis of nuclear parton distributions  

NASA Astrophysics Data System (ADS)

We present a new global QCD analysis of nuclear parton distribution functions and their uncertainties. In addition to the most commonly analyzed data sets for the deep-inelastic scattering of charged leptons off nuclei and Drell-Yan dilepton production, we include also measurements for neutrino-nucleus scattering and inclusive pion production in deuteron-gold collisions. The analysis is performed at next-to-leading order accuracy in perturbative QCD in a general mass variable flavor number scheme, adopting a current set of free nucleon parton distribution functions, defined accordingly, as reference. The emerging picture is one of consistency, where universal nuclear modification factors for each parton flavor reproduce the main features of all data without any significant tension among the different sets. We use the Hessian method to estimate the uncertainties of the obtained nuclear modification factors and examine critically their range of validity in view of the sparse kinematic coverage of the present data. We briefly present several applications of our nuclear parton densities in hard nuclear reactions at BNL-RHIC, CERN-LHC, and a future electron-ion collider.

de Florian, Daniel; Sassot, Rodolfo; Zurita, Pia; Stratmann, Marco

2012-04-01

147

Efficient and Ethical Response-Adaptive Randomization Designs for Multi-Arm Clinical Trials With Weibull Time-to-Event Outcomes.  

PubMed

We consider a design problem for a clinical trial with multiple treatment arms and time-to-event primary outcomes that are modeled using the Weibull family of distributions. The D-optimal design for the most precise estimation of model parameters is derived, along with compound optimal allocation designs that provide targeted efficiencies for various estimation problems and ethical considerations. The proposed optimal allocation designs are studied theoretically and are implemented using response-adaptive randomization for a clinical trial with censored Weibull outcomes. We compare the merits of our multiple-objective response-adaptive designs with traditional randomization designs and show that our designs are more flexible, realistic, generally more ethical, and frequently provide higher efficiencies for estimating different sets of parameters. PMID:24697678

Sverdlov, Oleksandr; Ryeznik, Yevgen; Wong, Weng-Kee

2014-01-01

148

Distribution System Analysis to support the Smart Grid  

Microsoft Academic Search

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

R. C. Dugan; R. F. Arritt; T. E. McDermott; S. M. Brahma; K. Schneider

2010-01-01

149

Elemental distribution analysis of urinary crystals.  

PubMed

Various crystals are seen in human urine. Some of them, particularly calcium oxalate dihydrate, are seen normally. Pathological crystals indicate crystal formation initiating urinary stones. Unfortunately, many of the relevant crystals are not recognized in light microscopic analysis of the urinary deposit performed in most of the clinical laboratories. Many crystals are not clearly identifiable under the ordinary light microscopy. The objective of the present study was to perform scanning electron microscopic (SEM) assessment of various urinary deposits and confirm the identity by elemental distribution analysis (EDAX). 50 samples of urinary deposits were collected from urinary stone clinic. Deposits containing significant crystalluria (more than 10 per HPF) were collected under liquid paraffin in special containers and taken up for SEM studies. The deposited crystals were retrieved with appropriate Pasteur pipettes, and placed on micropore filter paper discs. The fluid was absorbed by thicker layers of filter paper underneath and discs were fixed to brass studs. They were then gold sputtered to 100 A and examined under SEM (Jeol JSM 35C microscope). When crystals were seen, their morphology was recorded by taking photographs at different angles. At appropriate magnification, EDAX probe was pointed to the crystals under study and the wave patterns analyzed. Components of the crystals were recognized by utilizing the data. All the samples analyzed contained significant number of crystals. All samples contained more than one type of crystal. The commonest crystals encountered included calcium oxalate monohydrate (whewellite 22%), calcium oxalate dihydrate (weddellite 32%), uric acid (10%), calcium phosphates, namely, apatite (4%), brushite (6%), struvite (6%) and octocalcium phosphate (2%). The morphological appearances of urinary crystals described were correlated with the wavelengths obtained through elemental distribution analysis. Various urinary crystals that are not reported under light microscopy could be recognized by SEM-EDAX combination. EDAX is a significant tool for recognizing unknown crystals not identified by ordinary light microscopy or SEM alone. PMID:19536530

Fazil Marickar, Y M; Lekshmi, P R; Varma, Luxmi; Koshy, Peter

2009-10-01

150

Ceramics Analysis and Reliability Evaluation of Structures (CARES). Users and programmers manual  

NASA Technical Reports Server (NTRS)

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.

Nemeth, Noel N.; Manderscheid, Jane M.; Gyekenyesi, John P.

1990-01-01

151

Electron density distribution analysis for nitroguanidine  

SciTech Connect

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.

Ritchie, J.P.; Cromer, D.T.; Stewart, R.F.; Wasserman, H.J.; Ryan, R.R.

1985-01-01

152

Predictive Failure of Cylindrical Coatings Using Weibull Analysis.  

National Technical Information Service (NTIS)

Rotating, coated wiping rollers used in a high-speed printing application failed primarily from fatigue. Two coating materials were evaluated: a hard, cross-linked, plasticized polyvinyl chloride (PVC) and a softer, plasticized PVC. A total of 447 tests w...

B. L. Vlcek E. V. Zaretsky R. C. Hendricks

2002-01-01

153

Analysis of stratocumulus cloud fields using LANDSAT imagery: Size distributions and spatial separations  

NASA Technical Reports Server (NTRS)

Stratocumulus cloud fields in the FIRE IFO region are analyzed using LANDSAT Thematic Mapper imagery. Structural properties such as cloud cell size distribution, cell horizontal aspect ratio, fractional coverage and fractal dimension are determined. It is found that stratocumulus cloud number densities are represented by a power law. Cell horizontal aspect ratio has a tendency to increase at large cell sizes, and cells are bi-fractal in nature. Using LANDSAT Multispectral Scanner imagery for twelve selected stratocumulus scenes acquired during previous years, similar structural characteristics are obtained. Cloud field spatial organization also is analyzed. Nearest-neighbor spacings are fit with a number of functions, with Weibull and Gamma distributions providing the best fits. Poisson tests show that the spatial separations are not random. Second order statistics are used to examine clustering.

Welch, R. M.; Sengupta, S. K.; Chen, D. W.

1990-01-01

154

A critique of distributional analysis in the spatial model  

Microsoft Academic Search

Distributional analysis is widely used to study social choice in Euclidean models (35, 36, 1, 5, 11, 19, 8, 2, e.g). This method assumes a continuum of voters distributed according a probability measure. Since innite populations do not exist, the goal of distributional analysis is to give insight into the behavior of large nite populations. However, properties of nite populations

Craig A. Tovey

2010-01-01

155

Distribution system short circuit analysis-A rigid approach  

Microsoft Academic Search

The authors introduce a method of short-circuit analysis applicable to more rigid study of large-scale distribution systems. This approach is oriented toward applications in distribution system operation analysis. The solution method is an iterative compensation method, which uses a single optimally ordered factorization of the bus admittance matrix [YBus], commonly used in power flow analysis, to simulate the fault condition.

Tsai-Hsiang Chen; MO-Shing Chen; Wei-Jen Lee; Paul Kotas; Peter Van Olinda

1992-01-01

156

On the gap between an empirical distribution and an exponential distribution of waiting times for price changes in a financial market  

NASA Astrophysics Data System (ADS)

We analyze waiting times for price changes in a foreign currency exchange rate. Recent empirical studies of high-frequency financial data support that trades in financial markets do not follow a Poisson process and the waiting times between trades are not exponentially distributed. Here we show that our data is well approximated by a Weibull distribution rather than an exponential distribution in the non-asymptotic regime. Moreover, we quantitatively evaluate how much an empirical data is far from an exponential distribution using a Weibull fit. Finally, we discuss a transition between a Weibull-law and a power-law in the long time asymptotic regime.

Sazuka, Naoya

2007-03-01

157

Dynamic data distribution with control flow analysis  

Microsoft Academic Search

This paper describes the design of a data distribution tool which automatically derives the data mapping for the arrays and the parallelization strategy for the loops in a Fortran 77 program. The layout generated can be static or dynamic, and the distribution is one-dimensional BLOCK or CYCLIC. The tool takes into account the control flow statements in the code in

Jordi Garcia; Eduard Ayguade; Jesus Labarta

1996-01-01

158

Reference Wind Speed Distributions and Height Profiles for Wind Turbine Design and Performance Evaluation Applications.  

National Technical Information Service (NTIS)

The purpose of this report is to provide a set of reference or standard values of wind profiles, wind speed distributions and their effects on wind turbine performance for engineering design applications. Based on measured Weibull distribution parameters,...

A. Mikhail C. G. Justus W. R. Hargraves

1976-01-01

159

Power Flow Analysis for Balanced and Unbalanced Radial Distribution Systems  

Microsoft Academic Search

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

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

160

Comparative analysis for penetration of distributed generation in power systems  

Microsoft Academic Search

This paper addresses comparative analysis for penetration of distributed generation (DG) from the perspective of a distribution company (disco). Penetration of distributed generator (Size and location) is obtained through different approaches: Cost minimization and System Energy loss minimization. The methodology adopted permits the planner to decide optimal location and size of DG with compromise between System cost and System energy

Deependra Singh; K. S. Verma

2008-01-01

161

Analysis of Distribution Research and Development Planning.  

National Technical Information Service (NTIS)

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

L. Isaksen

1975-01-01

162

GIS-based poverty and population distribution analysis in China  

Microsoft Academic Search

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

Jing Cui; Yingjie Wang; Hong Yan

2009-01-01

163

A User-Oriented Power Distribution System Analysis Program.  

National Technical Information Service (NTIS)

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

J. A. Underwood

1976-01-01

164

An analysis of the dynamic behaviour of earnings distributions  

Microsoft Academic Search

An analysis of the dynamic behaviour of earnings distributions is conducted here in three ways. First, the method of dimensional analysis, in the context of Buckingham's Pi theorem, is employed to demonstrate that earnings distributions, which are almost always dynamic in character, should, under certain conditions and a special coordinate transformation, be self-similar and time-invariant. Application of the theorem to

Ruben D. Cohen

1998-01-01

165

Fracture mechanics concepts in reliability analysis of monolithic ceramics  

NASA Technical Reports Server (NTRS)

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.

Manderscheid, Jane M.; Gyekenyesi, John P.

1987-01-01

166

Distribution system short circuit analysis-a rigid approach  

Microsoft Academic Search

A rigid approach to short circuit analysis for large-scale distribution systems is introduced. The approach uses an individual (a-b-c) phase-based system representation, a nontrivial transformer model, and includes the contribution due to load. The method can, therefore, be applied to balanced or unbalanced, radial, network, or mixed-type distribution systems. This approach is oriented toward applications in distribution system operation analysis

Tsai-Hsiang Chen; Mo-Shing Chen; Wei-Jen Lee; Paul Kotas; Peter Van Olinda

1991-01-01

167

Global QCD Analysis of Fragmentation and Parton Distribution Functions  

SciTech Connect

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

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

2009-08-04

168

Flexural strength distribution of 3D SiC/SiC composite  

NASA Astrophysics Data System (ADS)

Flexural strength of a four-step, three-dimensional (3D) braiding SiC/SiC composite was tested at room temperature. The strength distribution was studied based on Weibull distribution and Normal distribution as well as examined by the Kolmogorov test. The results indicated that the flexural failure behavior of the composite was rather brittle with a small displacement. And the statistical strength distribution of the 3D SiC/SiC composite was in agreement with two-parameter Weibull distribution of the Weibull modulus, m=8.1545 and normal distribution. And the predicated mean flexural strength of the 3D SiC/SiC composite by the two-parameter Weibull distribution was consistent with the tested value.

Wu, Shoujun; Cheng, Laifei; Dong, Ning; Zhang, Litong; Xu, Yongdong

2006-12-01

169

A Framework for Callosal Fiber Distribution Analysis  

Microsoft Academic Search

This paper presents a framework for analyzing the spatial distribution of neural fibers in the brain, with emphasis on interhemispheric fiber bundles crossing through the corpus callosum. The proposed approach combines methodologies for fiber tracking and spatial normalization and is applied on diffusion tensor images and standard magnetic resonance images.

Dongrong Xu; Susumu Mori; Meiyappan Solaiyappan; Peter C. M. van Zijl; Christos Davatzikos

2002-01-01

170

DISTRIBUTION SYSTEM RELIABILITY ANALYSIS USING A MICROCOMPUTER  

EPA Science Inventory

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

171

Integer sparse distributed memory: analysis and results.  

PubMed

Sparse distributed memory is an auto-associative memory system that stores high dimensional Boolean vectors. Here we present an extension of the original SDM, the Integer SDM that uses modular arithmetic integer vectors rather than binary vectors. This extension preserves many of the desirable properties of the original SDM: auto-associativity, content addressability, distributed storage, and robustness over noisy inputs. In addition, it improves the representation capabilities of the memory and is more robust over normalization. It can also be extended to support forgetting and reliable sequence storage. We performed several simulations that test the noise robustness property and capacity of the memory. Theoretical analyses of the memory's fidelity and capacity are also presented. PMID:23747569

Snaider, Javier; Franklin, Stan; Strain, Steve; George, E Olusegun

2013-10-01

172

Economic analysis of efficient distribution transformer trends  

SciTech Connect

This report outlines an approach that will account for uncertainty in the development of evaluation factors used to identify transformer designs with the lowest total owning cost (TOC). The TOC methodology is described and the most highly variable parameters are discussed. The model is developed to account for uncertainties as well as statistical distributions for the important parameters. Sample calculations are presented. The TOC methodology is applied to data provided by two utilities in order to test its validity.

Downing, D.J.; McConnell, B.W.; Barnes, P.R.; Hadley, S.W.; Van Dyke, J.W.

1998-03-01

173

On the Weibull shape factor of intrinsic breakdown of dielectric films and its accurate experimental determination. Part II: experimental results and the effects of stress conditions  

Microsoft Academic Search

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

Ernest Y. Wu; J. Sune; W. Lai

2002-01-01

174

Analysis of Stress Distribution Beneath Embankments.  

National Technical Information Service (NTIS)

A mathematical analysis adapted to computer calculation is used to calculate stresses and displacements for complicated soil movements and for a large class of boundary conditions. Vertical stresses are found to be insensitive to variation in material pro...

T. W. Lambe R. C. Hirschfeld J. T. Christian

1966-01-01

175

A Comparison of Distribution Free and Non-Distribution Free Factor Analysis Methods  

ERIC Educational Resources Information Center

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…

Ritter, Nicola L.

2012-01-01

176

Analysis of models for the calculation of strength realization of aramide fibers in threads and microplastics  

Microsoft Academic Search

It has been shown in [2] that the strength of Aramide fibers can be described with a sufficient degree of accuracy by means of the statistical theory of strength [3]. Weibull's distribution was taken as the distribution function for the strength of monofibers, It was found that Weibull's function can be unimodal or bimodal, depending on the structure of the

L. V. Kompaniets; V. V. Potapov; G. A. Grigoryan; A. M. Kuperman; L. V. Puchkov; É. S. Zelenskii; É. V. Prut; N. S. Enikolopyan

1983-01-01

177

Simulation of probability distributions commonly used in hydrological frequency analysis  

NASA Astrophysics Data System (ADS)

Random variable simulation has been applied to many applications in hydrological modelling, flood risk analysis, environmental impact assessment, etc. However, computer codes for simulation of distributions commonly used in hydrological frequency analysis are not available in most software libraries. This paper presents a frequency-factor-based method for random number generation of five distributions (normal, log-normal, extreme-value type I, Pearson type III and log-Pearson type III) commonly used in hydrological frequency analysis. The proposed method is shown to produce random numbers of desired distributions through three means of validation: (1) graphical comparison of cumulative distribution functions (CDFs) and empirical CDFs derived from generated data; (2) properties of estimated parameters; (3) type I error of goodness-of-fit test. An advantage of the method is that it does not require CDF inversion, and frequency factors of the five commonly used distributions involves only the standard normal deviate. Copyright

Cheng, Ke-Sheng; Chiang, Jie-Lun; Hsu, Chieh-Wei

2007-01-01

178

Separating structural heterogeneities from stochastic variations in fluorescence resonance energy transfer distributions via photon distribution analysis.  

PubMed

We establish a probability distribution analysis (PDA) method for the analysis of fluorescence resonance energy transfer (FRET) signals to determine with high precision the originating value of a shot-noise-limited signal distribution. PDA theoretical distributions are calculated explicitly including crosstalk, stochastic variations, and background and represent the minimum width that a FRET distribution must have. In this way an unambiguous distinction is made between shot-noise distributions and distributions broadened by heterogeneities. This method simultaneously and effectively extracts highly resolved information from FRET distributions. The theoretical histograms match the exact profile of histograms generated from constant transfer efficiency experimental data with a chi2 near unity. The chi2 surface suggests an ultimate level of precision with FRET of < 1% of the Förster radius. Distributions of FRET signals in donor-acceptor-labeled DNA were unambiguously identified as being broader than shot-noise variations could explain. A model describing a Gaussian distribution of distances was tested with the PDA method and demonstrated 5 A inhomogeneities due to dye motions. The capability of this method to recover quantitative information from FRET distributions has potential applications for studying molecular conformations and dynamics. Potential sources for artifacts such as acceptor photobleaching, spectrally different observation volumes, and fluctuations of the Förster radius are ruled out. PMID:16571010

Antonik, Matthew; Felekyan, Suren; Gaiduk, Alexander; Seidel, Claus A M

2006-04-01

179

Surface flaw reliability analysis of ceramic components with the SCARE finite element postprocessor program  

NASA Technical Reports Server (NTRS)

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.

Gyekenyesi, John P.; Nemeth, Noel N.

1987-01-01

180

Statistical distribution of natural fractures and the possible physical generating mechanism  

NASA Astrophysics Data System (ADS)

We have fitted field measurements of fracture spacings (from the vicinity of Lake Strom Thurmond, Georgia, U.S.A.) to the Weibull, Schuhmann and fractal distributions. The fracture spacings follow a fractal and Weibull distribution which implies that they were formed as a result of a repetitive fragmentation process. The limited variation of the fracture density with orientation in the study area suggests that the stress distribution generating these fractures may be uniform.

Boadu, F. K.; Long, L. T.

1994-06-01

181

WATER DISTRIBUTION SYSTEM ANALYSIS: FIELD STUDIES, MODELING AND MANAGEMENT  

EPA Science Inventory

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

182

Electrical Power Distribution and Control Modeling and Analysis.  

National Technical Information Service (NTIS)

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 Powe...

I. S. Mehdi J. S. Fu M. Liffring

2001-01-01

183

Evaluation of various distributions for flood frequency analysis  

Microsoft Academic Search

A statistical model comprising nine different probability distri­ butions used especially for flood frequency analysis was applied to annual flood peak series with at least 30 observations for 11 unregulated streams in the Rhine Basin in Germany and two streams in Scotland. The para­ meters of most of those distributions were estimated by the methods of maximumlikelihoodandprobability-weightedmoments. The distributions were

TEFARUK HAKTANIR; HANS B. HORLACHER

1993-01-01

184

Karst database implementation in Minnesota: analysis of sinkhole distribution  

Microsoft Academic Search

This paper presents the overall sinkhole distributions and conducts hypothesis tests of sinkhole distributions and sinkhole formation using data stored in the Karst Feature Database (KFD) of Minnesota. Nearest neighbor analysis (NNA) was extended to include different orders of NNA, different scales of concentrated zones of sinkholes, and directions to the nearest sinkholes. The statistical results, along with the sinkhole

Y. Gao; E. C. Alexander Jr; R. J. Barnes

2005-01-01

185

Unified load flow analysis for emerging distribution systems  

Microsoft Academic Search

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

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

2010-01-01

186

Performance analysis of static locking in replicated distributed database systems  

NASA Technical Reports Server (NTRS)

Data replication and transaction deadlocks can severely affect the performance of distributed database systems. Many current evaluation techniques ignore these aspects, because it is difficult to evaluate through analysis and time consuming to evaluate through simulation. A technique is used that combines simulation and analysis to closely illustrate the impact of deadlock and evaluate performance of replicated distributed database with both shared and exclusive locks.

Kuang, Yinghong; Mukkamala, Ravi

1991-01-01

187

Performance analysis of static locking in replicated distributed database systems  

NASA Technical Reports Server (NTRS)

Data replications and transaction deadlocks can severely affect the performance of distributed database systems. Many current evaluation techniques ignore these aspects, because it is difficult to evaluate through analysis and time consuming to evaluate through simulation. Here, a technique is discussed that combines simulation and analysis to closely illustrate the impact of deadlock and evaluate performance of replicated distributed databases with both shared and exclusive locks.

Kuang, Yinghong; Mukkamala, Ravi

1991-01-01

188

A Weibull-PBPK model for assessing risk of arsenic-induced skin lesions in children  

Microsoft Academic Search

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

Chung-Min Liao; Tzu-Ling Lin; Szu-Chieh Chen

2008-01-01

189

A study on the ageing process for polyester resin using improved Weibull statistics  

Microsoft Academic Search

Surface tracking on organic solid insulators is one of the main reasons for failure in high voltage systems. Due to various factors, such as humidity, pollution, ice load, increase in local voltage, etc., it is hard to estime the lifetime of an insulator. For many years, Weibull statistics have been widely used and accepted as a successful mathematical method of

M. Ugur; A. Kuntman; A. Ersoy

2003-01-01

190

Investigation of the ageing process in polymeric insulators by using improved Weibull statistics  

Microsoft Academic Search

Surface tracking on organic solid insulators is one of the main reasons for failure in high voltage (HV) systems. Due to various factors, such as humidity, pollution, ice load, increase in local voltage, etc., it is hard to make an estimation about the life of an insulator. For many years Weibull statistics have been widely used and accepted as a

Mukden UGUR; Ayten KUNTMAN

2002-01-01

191

Analysis of Distribution Level Residential Demand Response  

SciTech Connect

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

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

2009-03-23

192

Modeling and analysis of solar distributed generation  

NASA Astrophysics Data System (ADS)

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.

Ortiz Rivera, Eduardo Ivan

193

Distribuicoes probabilisticas de velocidades do vento para avaliacao do potencial energetico eolico. (Probabilistic distributions of wind velocity for the evaluation of the wind power potential).  

National Technical Information Service (NTIS)

The theoretical model of wind speed distributions allow valuable information about the probability of events relative to the variable in study eliminating the necessity of a new experiment. The most used distributions has been the Weibull and the Rayleigh...

E. Z. Vendramini

1986-01-01

194

Integrating software architectures for distributed simulations and simulation analysis communities  

Microsoft Academic Search

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

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

2005-01-01

195

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

SciTech Connect

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

Tuffner, Francis K.; Singh, Ruchi

2011-08-09

196

Weibull master curves and fracture toughness testing Part III Master curves for the evaluation of dynamic Charpy impact tests  

Microsoft Academic Search

The existence of specimen-size-independent quasi-static Weibull master curves for macroscopically homogeneous solids characterizing strength and failure of both purely brittle materials and rather tough materials, which undergo an amount of stable crack growth prior to failure, has already been proved in earlier publications. In this paper, the concept of Weibull master curves is extended to the case of dynamic testing

M. Lambrigger

1999-01-01

197

A distribution short circuit analysis approach using hybrid compensation method  

Microsoft Academic Search

This paper addresses a new approach for real-time short circuit analysis of radial and weakly meshed distribution networks. The approach works based on a well documented radial power flow study method, and uses a hybrid compensation method to account for loops, PV nodes, and fault currents simultaneously. The three-phase short circuit analysis, in its actual a-b-c phase representation, can be

Xiaofeng Zhang; Farajollah Soudi; D. Shirmohammadi; C. S. Cheng

1995-01-01

198

Particle Size Analysis, Description and Analysis of Particle Size Distribution.  

National Technical Information Service (NTIS)

Particle size analysis and its use to measure mechanical processes of material conversion and property changes occuring during that conversion are studied. The linear measurements lie in the range from 0.01 to 0.1 microns and goes up to a few cm. Particle...

K. Leschonski

1974-01-01

199

Equal-gain and maximal-ratio combining over nonidentical Weibull fading channels  

Microsoft Academic Search

We study the performance of -branch equal-gain combining (EGC) and maximal-ratio combining (MRC) receivers operating over nonidentical Weibull-fading channels. Closed-form expressions are derived for the moments of the signal-to-noise ratio (SNR) at the output of the combiner and significant per- formance criteria, for both independent and correlative fading, such as average output SNR, amount of fading and spectral efficiency at

George K. Karagiannidis; Dimitris A. Zogas; Nikos C. Sagias; Stavros A. Kotsopoulos; George S. Tombras

2005-01-01

200

Rapid Analysis of Mass Distribution of Radiation Shielding  

NASA Technical Reports Server (NTRS)

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.

Zapp, Edward

2007-01-01

201

Analysis of water distribution systems using a perturbation method  

Microsoft Academic Search

The analysis of a water distribution network requires the solution of a set of nonlinear equations. The current methods are all iterative and require a good initial estimate to reach the solution quickly without any convergence problems. In this study a perturbation expansion is applied to the set of nonlinear equations to obtain a series of linear equations that can

H. A. Basha; B. G. Kassab

1996-01-01

202

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

Microsoft Academic Search

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

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

1999-01-01

203

An Economic Analysis of the Distribution of Police Patrol Forces.  

National Technical Information Service (NTIS)

The purpose of the study is to use the techniques of economic analysis to investigate the distribution of police among the various districts of a city. Police protection refers to resources used primarily for the purposes of crime control and prevention. ...

J. F. Giertz

1970-01-01

204

Distributed medical images analysis on a Grid infrastructure  

Microsoft Academic Search

In this paper medical applications on a Grid infrastructure, the MAGIC-5 Project, are presented and discussed. MAGIC-5 aims at developing Computer Aided Detection (CADe) software for the analysis of medical images on distributed databases by means of GRID Services. The use of automated systems for analyzing medical images improves radiologists' performance; in addition, it could be of paramount importance in

R. Bellottia; P. Cerellob; S. Tangaroa; V. Bevilacquan; M. Castellanon; G. Mastronardin; I. De Mitrih; G. De Nunzioi; G. Garganoa Faucif; A. Lauriag; E. Lopez Torresj; R. Magrof; G. L. Masalad; R. Massafraa; A. Preite Martineze; M. Quartak; G. Rasof; A. Reticoe; S. Stumbod; A. Tatae; S. Squarciao; E. Molinario; B. Canesio

205

Combining Probability Distributions From Experts in Risk Analysis  

Microsoft Academic Search

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

Robert T. Clemen; Robert L. Winkler

1999-01-01

206

Asymptotic Distributions of the Estimators of Communalities in Factor Analysis.  

ERIC Educational Resources Information Center

Asymptotic distributions of the estimators of communalities are derived for the maximum likelihood method in factor analysis. It is shown that equating the asymptotic standard error of the communality estimate to the unique variance estimate is not correct for the unstandardized case. Monte Carlo simulations illustrate the study. (SLD)

Ichikawa, Masanori

1992-01-01

207

Two-Dimensional Fluorescence Intensity Distribution Analysis: Theory and Applications  

Microsoft Academic Search

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

Peet Kask; Kaupo Palo; Nicolas Fay; Leif Brand; Ülo Mets; Dirk Ullmann; Joern Jungmann; Johannes Pschorr; Karsten Gall

2000-01-01

208

Shark: Fast Data Analysis Using Coarse-grained Distributed Memory.  

National Technical Information Service (NTIS)

Shark is a research data analysis system built on a novel coarse- grained distributed shared-memory abstraction. Shark marries query processing with deep data analy- sis, providing a uni ed system for easy data manipulation using SQL and pushing sophistic...

C. Engle

2013-01-01

209

Distributed response analysis of conductive behavior in single molecules  

PubMed Central

The ab initio computational approach of distributed response analysis is used to quantify how electrons move across conjugated molecules in an electric field, in analogy to conduction. The method promises to be valuable for characterizing the conductive behavior of single molecules in electronic devices.

in het Panhuis, Marc; Munn, Robert W.; Popelier, Paul L. A.; Coleman, Jonathan N.; Foley, Brian; Blau, Werner J.

2002-01-01

210

Pointers and linked lists in electric power distribution circuit analysis  

Microsoft Academic Search

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

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

1991-01-01

211

The MOST immersive approach for parallel and distributed program analysis  

Microsoft Academic Search

Examining a program's state during execution is of major importance for software developers when analyzing an application for performance tuning or error detection. This demand for suitable analysis tools is further pushed by parallel and distributed programs, which process huge amounts of complex data. A solution to this problem is offered by visualization, such that even a large amount of

Bernhard Reitinger; D. Kranzlmuller; Jens Volkert

2001-01-01

212

Adaptive walks and distribution of beneficial fitness effects.  

PubMed

We study the adaptation dynamics of a maladapted asexual population on rugged fitness landscapes with many local fitness peaks. The distribution of beneficial fitness effects is assumed to belong to one of the three extreme value domains, viz. Weibull, Gumbel, and Fréchet. We work in the strong selection-weak mutation regime in which beneficial mutations fix sequentially, and the population performs an uphill walk on the fitness landscape until a local fitness peak is reached. A striking prediction of our analysis is that the fitness difference between successive steps follows a pattern of diminishing returns in the Weibull domain and accelerating returns in the Fréchet domain, as the initial fitness of the population is increased. These trends are found to be robust with respect to fitness correlations. We believe that this result can be exploited in experiments to determine the extreme value domain of the distribution of beneficial fitness effects. Our work here differs significantly from the previous ones that assume the selection coefficient to be small. On taking large effect mutations into account, we find that the length of the walk shows different qualitative trends from those derived using small selection coefficient approximation. PMID:24274696

Seetharaman, Sarada; Jain, Kavita

2014-04-01

213

Analyzing Distributed Functions in an Integrated Hazard Analysis  

NASA Technical Reports Server (NTRS)

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.

Morris, A. Terry; Massie, Michael J.

2010-01-01

214

Sensitivity analysis for high quantiles of ochratoxin A exposure distribution.  

PubMed

Using available data from a consumption survey and contamination data on ochratoxin A (OA) in food, a sensitivity analysis (SA) for high quantiles (95th and 99th quantiles) of OA exposure distribution was carried out, obtained by a Monte Carlo simulation in French children. Exposure assessment for food contaminants is important to control the risk of foodborne diseases. Risk assessors are interested in high quantiles of contaminant exposure distributions. As these exposure distributions are generally very asymmetrical, it is difficult to obtain relevant and stable high quantiles in such a context. Determining OA exposure distribution is complex because it is based on the sum of elementary exposure distributions (eight foodstuffs are analysed here), and each one of these is the product of a consumption distribution and a contamination distribution. The SA enables us to quantify the influences of the parameter variability of the consumption and contamination probability density functions (pdf) which have been fitted to the data, our simulation model inputs, on the 95th and 99th quantiles of the output exposure distribution. After some preliminary trials, we have postulated a quadratic polynomial regression model for the quantiles of OA exposure distribution in view of undertaking this SA. This regression model comprises 32 main factors, their 496 two-factor interactions and their 32 quadratic terms. The 32 factors are the parameters of the fitted pdf: 16 parameters of Gamma distributions relative to the eight consumed foods and 16 parameters of Gamma distributions relative to the eight food OA contaminations. For an optimal parameter estimation of such a large model, we used an experimental design approach depending on a resolution-V fractional factorial design of 6561 experiments. The factor ranges are established by a preliminary study of bootstrap sampling. From the bootstrap samples, the factor ranges are obtained taking into account the correlation between the two parameters of the fitted Gamma pdf. A full exposure distribution is simulated for each of the 6561 experiments. The consumption dependencies are taken into account by the Iman and Conover method. On the basis of this analysis, validated and useful models for each desired quantile are obtained showing a major influence of the parameters of "Cereals" (consumption and contamination) and slightly less so for parameter of "Pork" consumption in the sensitivity of the quantiles. PMID:11999111

Albert, I; Gauchi, J P

2002-05-01

215

Parametrizing the local dark matter speed distribution: A detailed analysis  

NASA Astrophysics Data System (ADS)

In a recent paper, a new parametrization for the dark matter (DM) speed distribution f(v) was proposed for use in the analysis of data from direct detection experiments. This parametrization involves expressing the logarithm of the speed distribution as a polynomial in the speed v. We present here a more detailed analysis of the properties of this parametrization. We show that the method leads to statistically unbiased mass reconstructions and exact coverage of credible intervals. The method performs well over a wide range of DM masses, even when finite energy resolution and backgrounds are taken into account. We also show how to select the appropriate number of basis functions for the parametrization. Finally, we look at how the speed distribution itself can be reconstructed, and how the method can be used to determine if the data are consistent with some test distribution. In summary, we show that this parametrization performs consistently well over a wide range of input parameters and over large numbers of statistical ensembles and can therefore reliably be used to reconstruct both the DM mass and speed distribution from direct detection data.

Kavanagh, Bradley J.

2014-04-01

216

Distributed signal analysis of free-floating paraboloidal membrane shells  

NASA Astrophysics Data System (ADS)

Multifarious thin paraboloidal shell structures with unique geometric characteristics are utilized in aerospace, telecommunication and other engineering applications over the years. Governing equations of motion of paraboloidal shells are complicated and closed-form analytical solutions of these partial differential equations (PDEs) are difficult to derive. Furthermore, distributed monitoring technique and its resulting global sensing signals of thin flexible membrane shells are not well understood. This study focuses on spatially distributed modal sensing characteristics of free-floating flexible paraboloidal membrane shells laminated with distributed sensor patches based on a new set of assumed mode shape functions. In order to evaluate overall sensing/control effects, microscopic sensing signal characteristic, sensor segmentation and location of distributed sensors on thin paraboloidal membrane shells with different curvatures are investigated. Parametric analysis suggests that the signal generation depends on modal membrane strains in the meridional and circumferential directions in which the latter is more significant than the former, while all bending strains vanish in membrane shells. This study (1) demonstrates an analysis method for distributed sensors laminated on lightweight paraboloidal flexible structures and (2) identifies critical components and regions that generate significant signals for various shell modes.

Yue, H. H.; Deng, Z. Q.; Tzou, H. S.

2007-07-01

217

Integrating software architectures for distributed simulations and simulation analysis communities.  

SciTech Connect

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

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

2005-10-01

218

Influence Of Lateral Load Distributions On Pushover Analysis Effectiveness  

SciTech Connect

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

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

2008-07-08

219

Local structure studies of materials using pair distribution function analysis  

NASA Astrophysics Data System (ADS)

A collection of pair distribution function studies on various materials is presented in this dissertation. In each case, local structure information of interest pushes the current limits of what these studies can accomplish. The goal is to provide insight into the individual material behaviors as well as to investigate ways to expand the current limits of PDF analysis. Where possible, I provide a framework for how PDF analysis might be applied to a wider set of material phenomena. Throughout the dissertation, I discuss 0 the capabilities of the PDF method to provide information pertaining to a material's structure and properties, ii) current limitations in the conventional approach to PDF analysis, iii) possible solutions to overcome certain limitations in PDF analysis, and iv) suggestions for future work to expand and improve the capabilities PDF analysis.

Peterson, Joseph W.

220

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

221

Comparing Distributions of Environmental Outcomes for Regulatory Environmental Justice Analysis  

PubMed Central

Economists have long been interested in measuring distributional impacts of policy interventions. As environmental justice (EJ) emerged as an ethical issue in the 1970s, the academic literature has provided statistical analyses of the incidence and causes of various environmental outcomes as they relate to race, income, and other demographic variables. In the context of regulatory impacts, however, there is a lack of consensus regarding what information is relevant for EJ analysis, and how best to present it. This paper helps frame the discussion by suggesting a set of questions fundamental to regulatory EJ analysis, reviewing past approaches to quantifying distributional equity, and discussing the potential for adapting existing tools to the regulatory context.

Maguire, Kelly; Sheriff, Glenn

2011-01-01

222

Analysis of Large-Scale Distributed Information Systems  

Microsoft Academic Search

Studies the effects of correlations between the inter-arrival times of different service classes. An analysis of distributed information systems reveals that such inter-class correlations exist, in part as a result of the interactions between the server and its clients. To gain insight into the performance implications of these correlations, we formulate a general stochastic model that explicitly captures client-server interactions,

Joseph L. Hellerstein; T. S. Jayram; Mark S. Squillante

2000-01-01

223

Measuring Protein Synthesis by Mass Isotopomer Distribution Analysis (MIDA)  

Microsoft Academic Search

The measurement of protein kinetics by isotopic techniques has been hindered by the long-standing difficulty of accurately measuring the isotope content of the biosynthetic precursor pool (aminoacyl-tRNA in tissues). Mass isotopomer distribution analysis (MIDA) is a stable isotope-mass spectrometric (MS) technique for measuring biosynthetic precursor enrichments from measurements on a polymeric product, based on combinatorial probabilities of labeled and unlabeled

Christina Papageorgopoulos; Kenny Caldwell; Cedric Shackleton; Hans Schweingrubber; Marc K. Hellerstein

1999-01-01

224

Electrical Power Distribution and Control Modeling and Analysis  

NASA Technical Reports Server (NTRS)

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.

Fu, Johnny S.; Liffring, Mark; Mehdi, Ishaque S.

2001-01-01

225

Software component quality prediction in the legacy product development environment using Weibull and other mathematical distributions  

Microsoft Academic Search

Software component quality has a major influence in software development project performances such as lead-time, time to market and cost. It also affects the other projects within the organization, the people assigned into the projects and the organization in general. Software development organization must have indication and prediction about software component quality and project performances in general. One of the

Lovre Hribar

2009-01-01

226

Estimation of component and parameter distributions in spectral analysis.  

PubMed

A method is presented for estimating the distributions of the components and parameters determined with spectral analysis when it is applied to a single data set. The method uses bootstrap resampling to simulate the effect of noise on the computed spectrum and to correct for possible bias in the estimates. A number of bootstrap procedures are reviewed, and one is selected for application to the kinetic analysis of positron emission tomography dynamic studies. The technique is shown to require minimal assumptions about noise in the measurements, and its small sample properties are established through Monte-Carlo simulations. The advantages and limitations of spectral analysis with bootstrap resampling for deriving inferences for tracer kinetic modeling are illustrated through sample analyses of time-activity curves for [18F]fluorodeoxyglucose and [15O]-labeled water. PMID:9809510

Turkheimer, F; Sokoloff, L; Bertoldo, A; Lucignani, G; Reivich, M; Jaggi, J L; Schmidt, K

1998-11-01

227

PERISCOPE: An Online-Based Distributed Performance Analysis Tool  

NASA Astrophysics Data System (ADS)

This paper presents PERISCOPE - an online distributed performance analysis tool that searches for a wide range of performance bottlenecks in parallel applications. It consists of a set of agents that capture and analyze application and hardware-related properties in an autonomous fashion. The paper focuses on the Periscope design, the different search methodologies, and the steps involved to do an online performance analysis. A new graphical user-friendly interface based on Eclipse is introduced. Through the use of this new easy-to-use graphical interface, remote execution, selection of the type of analysis, and the inspection of the found properties can be performed in an intuitive and easy way. In addition, a real-world application, namely, the GENE code, a grand challenge problem of plasma physics is analyzed using Periscope. The results are illustrated in terms of found properties and scalability issues.

Benedict, Shajulin; Petkov, Ventsislav; Gerndt, Michael

228

Probabilistic Life and Reliability Analysis of Model Gas Turbine Disk  

NASA Technical Reports Server (NTRS)

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.

Holland, Frederic A.; Melis, Matthew E.; Zaretsky, Erwin V.

2002-01-01

229

Job optimization in ATLAS TAG-based distributed analysis  

NASA Astrophysics Data System (ADS)

The ATLAS experiment is projected to collect over one billion events/year during the first few years of operation. The efficient selection of events for various physics analyses across all appropriate samples presents a significant technical challenge. ATLAS computing infrastructure leverages the Grid to tackle the analysis across large samples by organizing data into a hierarchical structure and exploiting distributed computing to churn through the computations. This includes events at different stages of processing: RAW, ESD (Event Summary Data), AOD (Analysis Object Data), DPD (Derived Physics Data). Event Level Metadata Tags (TAGs) contain information about each event stored using multiple technologies accessible by POOL and various web services. This allows users to apply selection cuts on quantities of interest across the entire sample to compile a subset of events that are appropriate for their analysis. This paper describes new methods for organizing jobs using the TAGs criteria to analyze ATLAS data. It further compares different access patterns to the event data and explores ways to partition the workload for event selection and analysis. Here analysis is defined as a broader set of event processing tasks including event selection and reduction operations ("skimming", "slimming" and "thinning") as well as DPD making. Specifically it compares analysis with direct access to the events (AOD and ESD data) to access mediated by different TAG-based event selections. We then compare different ways of splitting the processing to maximize performance.

Mambelli, M.; Cranshaw, J.; Gardner, R.; Maeno, T.; Malon, D.; Novak, M.

2010-04-01

230

Distribution of molecular aggregation by analysis of fluctuation moments.  

PubMed Central

The fluorescence from an open volume of a solution of fluorescent molecules fluctuates as the molecules randomly diffuse into and out of the volume. The distribution of degrees of aggregation or polymerization of the fluorescent molecules can be characterized without perturbing the system by measuring either the moments or the amplitude distribution of these fluctuations. We present an experimental verification of this approach applied to simple model systems consisting of solutions of fluorescent particles of well-defined size. We have also characterized the response of the photon-detection device (typically a photomultiplier), which is essential to the analysis of the fluorescence fluctuations, and have compared two methods for determining shot-noise contributions.

Qian, H; Elson, E L

1990-01-01

231

Current Distribution Analysis of Insulated Gate Bipolar Transistor Cells  

NASA Astrophysics Data System (ADS)

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

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

2010-04-01

232

Distributions  

NSDL National Science Digital Library

This online, interactive lesson on distributions provides examples, exercises, and applets which explore the basic types of probability distributions and the ways distributions can be defined using density functions, distribution functions, and quantile functions.

Siegrist, Kyle

2008-12-24

233

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

NASA Astrophysics Data System (ADS)

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

Mulchrone, Kieran F.

2013-01-01

234

Numerical analysis of decoy state quantum key distribution protocols  

SciTech Connect

Decoy state protocols are a useful tool for many quantum key distribution systems implemented with weak coherent pulses, allowing significantly better secret bit rates and longer maximum distances. In this paper we present a method to numerically find optimal three-level protocols, and we examine how the secret bit rate and the optimized parameters are dependent on various system properties, such as session length, transmission loss, and visibility. Additionally, we show how to modify the decoy state analysis to handle partially distinguishable decoy states as well as uncertainty in the prepared intensities.

Harrington, Jim W [Los Alamos National Laboratory; Rice, Patrick R [Los Alamos National Laboratory

2008-01-01

235

Analysis of vegetation distribution in relation to surface morphology  

NASA Astrophysics Data System (ADS)

The scaling relationship between curvature, and local slope of a given point on the landscape and its drainage area reveal information about the dominant erosion processes over geomorphic time scales. Vegetation is known to influence erosion rates and landslide initiation, and also it is influenced by such processes and climatic regimes. Understanding the influence of vegetation dynamics on landscape organization is a fundamental challenge in the Earth Science field. In this study we considered two headwater catchments with vegetation mostly characterized by grass species (high altitude grassland), but also shrubs (mainly Alnus viridis), and high forest (mainly Picea abies) are common. We analyzed then the statistics related to vegetation distribution and different morphological patterns. High resolution LiDAR data served as the basis upon which derive Digital Terrain Models (DTMs) and mathematical attributes of landscape morphology including slope gradient, drainage area, aspect, surface curvature, topographic wetness index, slope - area and curvature - area loglog diagrams. The results reveal distinct differences in the curvature-area and slope-area relationships of each vegetation type. For a given drainage area, mean landscape slope is generally found to increase with woody vegetation. Profound landsliding signature is detected in areas interested by Alnus viridis distribution, thus underlining the relation between such pioneer species with slope instability. This preliminary analysis suggested that, when high resolution topography is available, is possible to better characterize the vegetation distribution based on surface morphology thus providing a useful tool for better understanding the processes and the role of vegetation in the landscape evolution.

Savio, Francesca; Prosdocimi, Massimo; Tarolli, Paolo; Rulli, Cristina

2013-04-01

236

Analysis of Fuel Ethanol Transportation Activity and Potential Distribution Constraints  

SciTech Connect

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

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

2010-01-01

237

Data intensive high energy physics analysis in a distributed cloud  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

238

Evaluation of Distribution Analysis Software for DER Applications  

SciTech Connect

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

Staunton, RH

2003-01-23

239

Power flow study and voltage stability analysis for distribution systems with distributed generation  

Microsoft Academic Search

The voltage instability phenomena may occur in distribution networks. The decline of voltage stability level will restrict the increase of load served by distribution companies. Distributed generation (DG) is increasingly drawing great attention of people. The development of DGs will bring new chances to traditional power systems. DGs connected to distribution networks are potential to improve the system voltage stability.

Haiyan Chen; Jinfu Chen; Dongyuan Shi; Xianzhong Duan

2006-01-01

240

Prediction of the Inert Strength Distribution of Si3N4 Diesel Valves  

SciTech Connect

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

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

1999-01-25

241

Analysis of the Spectral Energy Distributions of Fermi bright blazars  

SciTech Connect

Blazars are a small fraction of all extragalactic sources but, unlike other objects, they are strong emitters across the entire electromagnetic spectrum. In this study we have conducted a detailed investigation of the broad-band spectral properties of the gamma-ray selected blazars of the Fermi LAT Bright AGN Sample (LBAS). By combining the accurately estimated Fermi gamma-ray spectra with Swift, radio, NIR-Optical and hard-X/gamma-ray data, collected within three months of the LBAS data taking period, we were able to assemble high-quality and quasi-simultaneous Spectral Energy Distributions (SED) for 48 LBAS blazars. Here we show the procedure for the multi wavelength analysis.

Gasparrini, D.; Cutini, S. [ASI Science Data Center, ASDC, ESRIN, Frascati (Italy); Consorzio interuniversitario per la Fisica Spaziale (CIFS), Torino (Italy); Colafrancesco, S.; Giommi, P. [ASI Science Data Center, ASDC, ESRIN, Frascati (Italy); Agenzia Spaziale Italiana, Roma (Italy); Raino, S. [Dipartimento di Fisica, 'M.Merlin' dell' Universita e del Politecnico di Bari (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Bari, 70126 Bari (Italy)

2010-03-26

242

Theoretical stability analysis of quantum dash distributed Bragg reflector lasers  

NASA Astrophysics Data System (ADS)

A detailed theoretical analysis of stability in a quantum dash distributed Bragg reflector (DBR) laser is presented under the small-signal condition. The influence of p-type doping and inhomogeneous line broadening on the hysteresis width of the quantum dash DBR laser is studied using a rate equation model that includes all of the multidiscrete energy levels in the valence and conduction bands. Our calculations show that a large hysteresis width is obtained by detuning the laser by ~10 meV above the ground state energy and doping the dashes by acceptor concentration NA=3.7×1017 cm-3. Also we find that a large self-pulsation frequency is obtained by detuning the laser by -15 meV from the ground state energy and doping the dashes by NA=2.5×1017 cm-3. The laser hysteresis width can be greatly reduced by doping the dashes with NA>1×1018 cm-3.

Qasaimeh, Omar; Qasaimeh, Hadeel

2009-12-01

243

A Distributed Flocking Approach for Information Stream Clustering Analysis  

SciTech Connect

Intelligence analysts are currently overwhelmed with the amount of information streams generated everyday. There is a lack of comprehensive tool that can real-time analyze the information streams. Document clustering analysis plays an important role in improving the accuracy of information retrieval. However, most clustering technologies can only be applied for analyzing the static document collection because they normally require a large amount of computation resource and long time to get accurate result. It is very difficult to cluster a dynamic changed text information streams on an individual computer. Our early research has resulted in a dynamic reactive flock clustering algorithm which can continually refine the clustering result and quickly react to the change of document contents. This character makes the algorithm suitable for cluster analyzing dynamic changed document information, such as text information stream. Because of the decentralized character of this algorithm, a distributed approach is a very natural way to increase the clustering speed of the algorithm. In this paper, we present a distributed multi-agent flocking approach for the text information stream clustering and discuss the decentralized architectures and communication schemes for load balance and status information synchronization in this approach.

Cui, Xiaohui [ORNL; Potok, Thomas E [ORNL

2006-01-01

244

Reliability analysis of a structural ceramic combustion chamber  

NASA Technical Reports Server (NTRS)

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.

Salem, Jonathan A.; Manderscheid, Jane M.; Freedman, Marc R.; Gyekenyesi, John P.

1990-01-01

245

Reliability analysis of a structural ceramic combustion chamber  

NASA Technical Reports Server (NTRS)

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.

Salem, Jonathan A.; Manderscheid, Jane M.; Freedman, Marc R.; Gyekenyesi, John P.

1991-01-01

246

An Open Architecture for Distributed Malware Collection and Analysis  

NASA Astrophysics Data System (ADS)

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.

Cavalca, Davide; Goldoni, Emanuele

247

Application of Principal Component Analysis to the Analysis of Atmospheric Aerosol Size Distributions  

NASA Astrophysics Data System (ADS)

Atmospheric size distributions provide important fundamental information for studying atmospheric particle physics. To capture enough information using a distribution with reasonable resolution results in massive data sets. For example, 5-minute scans with 30 size bins produces 8640 data points per day. The complexity of such data set usually creates difficulties in data handling and interpretation. Principal Component Analysis (PCA) provides a way to reduce the dimensionality of data sets and produces a simpler yet quantitatively equivalent data set. The simplified data set usually provides an easier mean for data interpretation. In applying PCA to size distribution data, there are several important aspects that one needs to pay attention to. These include proper weighting for the data, correct selection of the number of components to extract and a rotation scheme to transform the result to simple structure for interpretation. In this poster, these important issues in applying PCA to size distribution data will be discussed. A new weighting scheme for size distribution data has been developed. This new weighting scheme allows one to fit the size distribution data more accurately without requiring too many components. Application of Varimax rotation to the eigenvectors enables one to turn the eigenvectors to a simple and physically meaningful size distribution function. As a result, a complete distribution can be broken down into a series of simple and independent distributions for easy interpretation. Furthermore, procedure on how to extract the correct number of components will be addressed. Finally, some field study measurements from Pacific 2001 and other studies held in Southern Ontario will be used as an illustration of how to make use of the rotated scores to explain some atmospheric process such as local nucleation and transport.

Chan, T. W.; Mozurkewich, M.

2003-12-01

248

Quantitative energy-filtered image analysis in cytochemistry. II. Morphometric analysis of element-distribution images.  

PubMed

A combination of energy-filtered electron microscopy (EFEM) and an image-analysis system (IBAS/2000) is used for a morphometric analysis of chemical reaction products in cells. Electron energy-loss spectroscopic element-distribution images are acquired from cytochemical reaction products in a variety of cellular objects: (1) colloidal thorium particles in extra-cellular coat material, (2) iron-containing ferritin particles in liver parenchymal cells, (3) barium-containing reaction products in endoplasmic reticulum stacks, (4) elements present in lysosomal cerium- and barium-containing precipitates connected with acid phosphatase (AcPase) or aryl sulphatase (AS) enzyme activity. Areas or area fractions are determined from such element-distribution images by application of an objective image segmentation method. By superposition of two or more element-distribution images, mutual element relations are qualitatively established in lysosomal cerium- and barium-containing precipitates connected with acid phosphatase (AcPase) or aryl sulphatase (AS) enzyme activity. By comparing electron spectroscopic images (ESI) with element-distribution images, the mutual contrast per element relations are quantitatively investigated. The obtained gain in resolution in such electron energy-loss spectroscopic element-distribution images will be explained and discussed. PMID:2336735

Sorber, C W; Van Dort, J B; Ringeling, P C; Cleton-Soeteman, M I; De Bruijn, W C

1990-01-01

249

Spectral Analysis of Distributions: Finding Periodic Components in Eukaryotic Enzyme Length Data  

Microsoft Academic Search

We introduce the spectral analysis of distributions (SAD), a method for detecting and eval- uating possible periodicity in experimental data distributions (histograms) of arbitrary shape. SAD determines whether a given empirical distribution contains a periodic compo- nent. We also propose a system of probabilistic mixture distributions to model a histogram consisting of a smooth background together with peaks at periodic

Eugene Kolker; Brian C. Tjaden; Robert Hubley; Edward N. Trifonov; Andrew F. Siegel

2002-01-01

250

Unsymmetrical Short-Circuit Fault Analysis for Weakly Meshed Distribution Systems  

Microsoft Academic Search

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

Jen-Hao Teng

2010-01-01

251

Crystal Size Distribution analysis of Merapi Andesites and cogenetic inclusions  

NASA Astrophysics Data System (ADS)

Mt. Merapi in Central Java, Indonesia, is one of the most active stratovolcanoes on Earth [1]. Previous petrographic and geochemical studies [e.g. 2-4] identified the presence of a large plumbing system with a complex and multiphase history involving accumulation, magma mixing, crustal assimilation, equilibration and degassing. This study uses Crystal Size Distribution (CSD) analysis [5, 6] of recent Merapi eruptive products to assess if the different crystal populations and the complex history identified by geochemical techniques can be resolved by CSD. Moreover, CSD analysis can give additional information on processes occurring during storage and ascent as well as information on the timing of such processes [5, 6]. CSD analyses of plagioclase in four Merapi andesites indicate the presence of two main crystal populations. However, geochemical studies identified up to four plagioclase crystal types based on major and isotope chemistry. The comparison of isotope and major element transects with the CSD analyses indicate that phenocrysts >2 mm, represent a period of crystal growth that involved accumulation and crustal assimilation. This is followed by textural re-equilibration and a second phase of crystal growth, represented by plagioclase phenocrysts and microcrysts <2 mm in size. CSDs of igneous medium to coarse grained cogenetic inclusions indicate a third <1 mm crystal population, potentially indicating induced decompressional crystallisation by degassing and amphibole breakdown, and or crustal assimilation. Secondary processes such as resorption and compaction are recorded in the omission of intermediate crystal sizes in CSD plots for some igneous inclusions. Although CSD analysis provides additional information about processes that occur beneath Merapi, petrographic and geochemical information were required to draw unique conclusions. Fluctuations in magma chamber conditions recorded by crystal geochemistry did not always form a new textural crystal population resolvable by CSD analysis. Merapi has a long eruptive history with emission of significant volumes of magma and regular replenishment. In order to produce the relatively homogenised whole rock and CSD data a large steady state magmatic system beneath Merapi is required. References: [1] Voight et al., 2000, J. Volcanol. Geotherm. Res. 100, 1-8 [2] Hammer et al., 2000, J. Volcanol. Geotherm. Res. 100, 165-192 [3] Gertisser & Keller, 2003, J. Petrol. 44, 457-489 [4] Chadwick et al., 2007, J. Petrol. 48, 1793-1812 [5] Chadwick, 2008, PhD Thesis, University Dublin [6] Marsh, 1988, Cont. Mineral. Petrol. 99, 277-291 [7] Higgins, 2006, Cambridge University Press

van der Zwan, F. M.; Chadwick, J. P.; Troll, V. R.

2009-04-01

252

Modeling and analysis of PEMFC in distributed generation system  

Microsoft Academic Search

With the rising of distributed generation technology, fuel cell, as an important distributed generation source, has become increasingly attractive by virtue of their inherently clean, efficient and quiet service. The dynamic characteristics of distributed generation system lie largely on the property of DG sources in it. Firstly, the dynamic characteristics of the fuel cell in small, medium and large timescale

Bibin Huang; Peng Li; Dan Wang; Fei Ding; Chengshan Wang

2009-01-01

253

A mathematical analysis of the DCT coefficient distributions for images  

Microsoft Academic Search

Over the past two decades, there have been various studies on the distributions of the DCT coefficients for images. However, they have concentrated only on fitting the empirical data from some standard pictures with a variety of well-known statistical distributions, and then comparing their goodness of fit. The Laplacian distribution is the dominant choice balancing simplicity of the model and

Edmund Y. Lam; Joseph W. Goodman

2000-01-01

254

Distribution and Phylogenetic Analysis of Family 19 Chitinases in Actinobacteria  

PubMed Central

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

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

2004-01-01

255

Failure Rate Analysis of Boeing 737 Brakes Employing Neural Network  

Microsoft Academic Search

The failure rate analysis of brake assemblies of a commercial airplane, i.e., Boeing 737, is analyzed using the artificial neural network and Weibull regression models. One-layered feed-forward back- propagation algorithm for artificial neural network whereas three parameters model for Weibull are used for the analysis. Three years of data are used for model building and validation. The results show that

Ahmed Z. Al-Garni; Ahmad Jamal; Farooq Saeed; Ayman H. Kassem

256

A distributed analysis of Human impact on global sediment dynamics  

NASA Astrophysics Data System (ADS)

Understanding riverine sediment dynamics is an important undertaking for both socially-relevant issues such as agriculture, water security and infrastructure management and for scientific analysis of landscapes, river ecology, oceanography and other disciplines. Providing good quantitative and predictive tools in therefore timely particularly in light of predicted climate and landuse changes. Ever increasing human activity during the Anthropocene have affected sediment dynamics in two major ways: (1) an increase is hillslope erosion due to agriculture, deforestation and landscape engineering and (2) trapping of sediment in dams and other man-made reservoirs. The intensity and dynamics between these man-made factors vary widely across the globe and in time and are therefore hard to predict. Using sophisticated numerical models is therefore warranted. Here we use a distributed global riverine sediment flux and water discharge model (WBMsed) to compare a pristine (without human input) and disturbed (with human input) simulations. Using these 50 year simulations we will show and discuss the complex spatial and temporal patterns of human effect on riverine sediment flux and water discharge.

Cohen, S.; Kettner, A.; Syvitski, J. P.

2012-12-01

257

Fourier analysis of polar cap electric field and current distributions  

NASA Technical Reports Server (NTRS)

A theoretical study of high-latitude electric fields and currents, using analytic Fourier analysis methods, is conducted. A two-dimensional planar model of the ionosphere with an enhanced conductivity auroral belt and field-aligned currents at the edges is employed. Two separate topics are treated. A field-aligned current element near the cusp region of the polar cap is included to investigate the modifications to the convection pattern by the east-west component of the interplanetary magnetic field. It is shown that a sizable one-cell structure is induced near the cusp which diverts equipotential contours to the dawnside or duskside, depending on the sign of the cusp current. This produces characteristic dawn-dusk asymmetries to the electric field that have been previously observed over the polar cap. The second topic is concerned with the electric field configuration obtained in the limit of perfect shielding, where the field is totally excluded equatorward of the auroral oval. When realistic field-aligned current distributions are used, the result is to produce severely distorted, crescent-shaped equipotential contours over the cap. Exact, analytic formulae applicable to this case are also provided.

Barbosa, D. D.

1984-01-01

258

CRACK GROWTH ANALYSIS OF SOLID OXIDE FUEL CELL ELECTROLYTES  

SciTech Connect

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

S. Bandopadhyay; N. Nagabhushana

2003-10-01

259

Development and Distribution of Data Analysis Reduction Tools: the ISOPHOT Interactive Analysis Case  

NASA Astrophysics Data System (ADS)

The different interactive data analysis software packages (``xIA'': CIA, LIA, PIA, SIA) developed for the ISO instruments were conceived primarily as calibration tools. However, all of them were used more and more for astronomical data reduction throughout the mission, imposing new requirements on user friendliness, documentation, distribution, compatibility and user help systems. The strategies followed in the case of the ISOPHOT Interactive Analysis as well as the achieved experiences, valuable in every current and future observatory, will be discussed in this paper.

Gabriel, C.

260

Bayesian estimation of generalized exponential distribution under noninformative priors  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

261

Performance Analysis of Distributed Fuzzy CA-CFAR Detector in Pearson Distributed Clutter  

Microsoft Academic Search

In order to improve the radar's detection performance under Pearson distributed background clutter, the problem of designing CA-CFAR detector based on fuzzy logic is studied in this paper. A kind of distributed fuzzy CA-CFAR detection scheme including two detectors is proposed here. Two detectors compute the values of the membership function to the false alarm space from the samples of

Long Cai; Xiaochuan Ma; Chengpeng Hao; Xiaoguang Yang

2009-01-01

262

Modeling and performance analysis of fuzzy based distributed generation supported distribution system  

Microsoft Academic Search

The traditional approach in an electrical power system is to have centralized large capacity power plants feeding power to distant load centers through an extensive transmission and distribution network. DG emerged as an alternative to upgrade transmission lines and increase the capacity of remote power plants. The connection of DG to a Distribution system meets the various challenges like power

S. S. Darly; P. Vanaja Ranjan; K. V. Bindu; A. Srikrishnan; P. R. Krishnan; B. J. Rabi

2010-01-01

263

Frequency distribution histograms for the rapid analysis of data  

NASA Technical Reports Server (NTRS)

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.

Burke, P. V.; Bullen, B. L.; Poff, K. L.

1988-01-01

264

Statistical distribution of mechanical properties for three graphite-epoxy material systems  

NASA Technical Reports Server (NTRS)

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.

Reese, C.; Sorem, J., Jr.

1981-01-01

265

Bivariate extreme value distributions  

NASA Technical Reports Server (NTRS)

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.

Elshamy, M.

1992-01-01

266

Analysis and calculation of load distribution for slewing bearing  

Microsoft Academic Search

The research of load distribution is not only an important part of bearing theory but the basis of studying the other performance indicators of bearings as well. Based on the contact theory of Hertz, the relation of geometric deformation of slewing bearing under certain loads is analyzed, and an analytical formula of load distribution for the slewing bearing under the

Li Yunfeng; Chen Hongtao

2011-01-01

267

A global analysis of root distributions for terrestrial biomes  

Microsoft Academic Search

Understanding and predicting ecosystem functioning (e.g., carbon and water fluxes) and the role of soils in carbon storage requires an accurate assessment of plant rooting distributions. Here, in a comprehensive literature synthesis, we analyze rooting patterns for terrestrial biomes and compare distributions for various plant functional groups. We compiled a database of 250 root studies, subdividing suitable results into 11

R. B. Jackson; J. Canadell; J. R. Ehleringer; H. A. Mooney; O. E. Sala; E. D. Schulze

1996-01-01

268

Evaluation of Distribution Analysis Software for DER Applications  

Microsoft Academic Search

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

Staunton

2003-01-01

269

Analysis of Parallel Downloading for Large File Distribution  

Microsoft Academic Search

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

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

2003-01-01

270

Analysis Model for Domestic Hot Water Distribution Systems: Preprint  

SciTech Connect

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.

Maguire, J.; Krarti, M.; Fang, X.

2011-11-01

271

Analysis of a class of distributed delay logistic differential equations  

Microsoft Academic Search

In this paper, we consider the illustrative example of generalised logistic equations where the carrying-capacity effect is modelled by a distributed-delay effect (which may be over the infinite past). These distributed delay differential equations, though simple in structure, possess a rich array of solutions. If the delay is sufficiently large a supercritical Hopf bifurcation occurs, which finally disappears asymptotically when

J. Donaldson

2003-01-01

272

Performance of dual maximal ratio combining diversity in nonidentical correlated Weibull fading channels using Pade\\/spl acute\\/ approximation  

Microsoft Academic Search

In this letter, we evaluate the performance of the dual-branch maximal ratio combining (MRC) diversity scheme in nonidentical correlated Weibull fading channels with arbitrary parameters. We first use the Pade´ approximation (PA) to find closed-form rational expressions for the moment generating function (MGF) of the output signal-to-noise ratio (SNR) of the MRC receiver. Different performance measures, such as the outage

Mahmoud H. Ismail; Mustafa M. Matalgah

2006-01-01

273

Analysis of temperature distribution in liquid-cooled turbine blades  

NASA Technical Reports Server (NTRS)

The temperature distribution in liquid-cooled turbine blades determines the amount of cooling required to reduce the blade temperature to permissible values at specified locations. This report presents analytical methods for computing temperature distributions in liquid-cooled turbine blades, or in simplified shapes used to approximate sections of the blade. The individual analyses are first presented in terms of their mathematical development. By means of numerical examples, comparisons are made between simplified and more complete solutions and the effects of several variables are examined. Nondimensional charts to simplify some temperature-distribution calculations are also given.

Livingood, John N B; Brown, W Byron

1952-01-01

274

Power distribution, the environment, and public health: A state-level analysis  

Microsoft Academic Search

This paper examines relationships among power distribution, the environment, and public health by means of a cross-sectional analysis of the 50 US states. A measure of inter-state variations in power distribution is derived from data on voter participation, tax fairness, Medicaid access, and educational attainment. We develop and estimate a recursive model linking the distribution of power to environmental policy,

James K. Boyce; Andrew R. Klemer; Paul H. Templet; Cleve E. Willis

1999-01-01

275

Fluorescence-Intensity Distribution Analysis and Its Application in Biomolecular Detection Technology  

Microsoft Academic Search

A methodology, fluorescence-intensity distribution analysis, has been developed for confocal microscopy studies in which the fluorescence intensity of a sample with a heterogeneous brightness profile is monitored. An adjustable formula, modeling the spatial brightness distribution, and the technique of generating functions for calculation of theoretical photon count number distribution serve as the two cornerstones of the methodology. The method permits

Peet Kask; Kaupo Palo; Dirk Ullmann; Karsten Gall

1999-01-01

276

Specification and testing of a comprehensive strategic analysis framework for distributed generation  

Microsoft Academic Search

This paper presents a framework for analysing the impact of distributed generation scenarios on distribution networks and businesses. The framework has been designed using knowledge gained from power industry experts through the use of knowledge engineering techniques. The expert knowledge acquired relating to distributed generation has been carefully structured to enable the specification of a comprehensive analysis framework. This framework

G. W. Ault; A. Cruden; J. R. McDonald

2000-01-01

277

Determination analysis of energy conservation standards for distribution transformers  

SciTech Connect

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

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

1996-07-01

278

Development of distribution system reliability and risk analysis models  

NASA Astrophysics Data System (ADS)

The overall objectives of a research project were to: determine distribution reliability assessment methods currently used by the industry; develop a general outage reporting scheme suitable for a wide variety of distributing utilities (reliability model); develop a model for predicting the reliability of future system configurations (risk model); and compile a handbook of reliability assessment methods designed specifically for use by the practicing distribution engineer. Emphasis was placed on compiling and organizing reliability assessment techniques presently used by the industry. The project examined reliability evaluation from two perspectives: historical and predictive assessment. Two reliability assessment models, HISRAM - the historical reliability assessment model and PRAM - the predictive reliability assessment model were developed. Each model was tested in a utility environment by the Duquesne Light Company and the Public Service Electric and Gas Company of New Jersey. A survey of 56 diverse utilities served as a basis for examining current distribution reliability assessment practices in the electric power industry.

Northcote-Green, J. E. D.; Vismor, T. D.; Brooks, C. L.

1981-08-01

279

Industry Sector Analysis Mexico: Electric Power Production and Distribution Equipment.  

National Technical Information Service (NTIS)

The Industry Sector Analyses (I.S.A.) for electric power production and distribution equipment contains statistical and narrative information on projected market demand, end-users, receptivity of Mexican consumers to U.S. products, the competitive situati...

J. S. Wood R. W. Miller

1988-01-01

280

Analysis of Small Water Management Structures in Irrigation Distribution Systems.  

National Technical Information Service (NTIS)

The intent of the report has been to sort through the large volume of literature in an attempt to define the specific research needs regarding small water management structures used in irrigation distribution systems. In particular, the emphasis has been ...

G. V. Skogerboe W. R. Walker B. B. Hacking L. H. Austin

1969-01-01

281

Vibration Analysis of Rotating Machinery Using the Spectral Distribution Function  

NASA Astrophysics Data System (ADS)

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.

Davis, S. S.

1998-07-01

282

Diffractive parton distributions from the analysis with higher twist  

SciTech Connect

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

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

2009-03-23

283

Reference wind speed distributions and height profiles for wind turbine design and performance evaluation applications. [USA  

Microsoft Academic Search

The purpose of this report is to provide a set of reference or standard values of wind profiles, wind speed distributions and their effects on wind turbine performance for engineering design applications. Based on measured Weibull distribution parameters, representative average, low, and high variance data are given for height profiles of mean, 25 percentile, and 75 percentile wind speeds; and

C. G. Justus; W. R. Hargraves; A. Mikhail

1976-01-01

284

Statistical analysis and modelling of small satellite reliability  

NASA Astrophysics Data System (ADS)

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.

Guo, Jian; Monas, Liora; Gill, Eberhard

2014-05-01

285

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

ERIC Educational Resources Information Center

In the article "Exploring the Sensitivity of Horn's Parallel Analysis to the Distributional Form of Random Data," Dinno (this issue) provides strong evidence that the distribution of random data does not have a significant influence on the outcome of the analysis. Hayton appreciates the thorough approach to evaluating this assumption, and agrees…

Hayton, James C.

2009-01-01

286

Reconfirmation of the Three-Domain Classification of Life by Cluster Analysis of Protein Length Distributions  

NASA Astrophysics Data System (ADS)

The classification of life should be based on the intrinsic mechanism in the evolution of life. We found new methods to classify life into Archaea, Bacteria and Eucarya based on the correlation analysis and spectral analysis of protein length distributions. We show that there is rich evolutionary information stored in the fluctuations of protein length distributions. The intrinsic mechanism of diversification of life is revealed by the properties of protein length distributions.

Li, Dirson Jian; Zhang, Shengli

287

ERDA analysis of the depth distribution of deuterium in ion-irradiated nickel  

Microsoft Academic Search

Elastic recoil detection analysis (ERDA) using 16 MeV 16O5+ ions as a probe, was applied to measure depth distribution of implanted deuterium in polycrystalline nickel specimens. Depth distribution of deuterium in helium pre-irradiated nickel at room temperature was in good agreement with the calculated damage distribution induced by the deuterium and helium ions, while no adequate correlation of deuterium distribution

Tohru Mitamura; Mititaka Terasawa; Kumiko Arashi; L. Liu; Shunya Yamamoto; Peter Goppelt-Langer; Hidefumi Takeshita; Yasushi Aoki; Hiroshi Naramoto

1997-01-01

288

A fractal approach to dynamic inference and distribution analysis  

PubMed Central

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

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

2013-01-01

289

Inductance and Current Distribution Analysis of a Prototype HTS Cable  

NASA Astrophysics Data System (ADS)

This project is partly supported by NSFC Grant 51207146, RAEng Research Exchange scheme of UK and EPSRC EP/K01496X/1. Superconducting cable is an emerging technology for electricity power transmission. Since the high power capacity HTS transmission cables are manufactured using a multi-layer conductor structure, the current distribution among the multilayer structure would be nonuniform without proper optimization and hence lead to large transmission losses. Therefore a novel optimization method has been developed to achieve evenly distributed current among different layers considering the HTS cable structure parameters: radius, pitch angle and winding direction which determine the self and mutual inductance. A prototype HTS cable has been built using BSCCO tape and tested to validate the design the optimal design method. A superconductor characterization system has been developed using the Labview and NI data acquisition system. It can be used to measure the AC loss and current distribution of short HTS cables.

Zhu, Jiahui; Zhang, Zhenyu; Zhang, Huiming; Zhang, Min; Qiu, Ming; Yuan, Weijia

2014-05-01

290

Sampling error in the bending strength distribution of dimension lumber  

Microsoft Academic Search

Summary  Information is presented on the magnitude of errors associated with various sampling simulation schemes of the distribution\\u000a of three different populations, representing actual bending strength of dimension lumber. Errors were determined between the\\u000a simulated and actual distributions. Graphical evaluations indicated good fits with the three-parameter form of the weibull\\u000a distribution for both original and simulated bending strength data, as well

P. J. Pellicane; J. Bodig

1981-01-01

291

Evaluation of frequency distributions for flood hazard analysis  

USGS Publications Warehouse

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

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

1995-01-01

292

Distributional Assumptions in Educational Assessments Analysis: Normal Distributions versus Generalized Beta Distribution in Modeling the Phenomenon of Learning  

ERIC Educational Resources Information Center

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…

Campos, Jose Alejandro Gonzalez; Moraga, Paulina Saavedra; Del Pozo, Manuel Freire

2013-01-01

293

Analysis of tablet compaction. II. Finite element analysis of density distributions in convex tablets.  

PubMed

A Drucker-Prager/cap constitutive model, where the elastic and plastic model parameters are expressed as a function of relative density (RD), was presented in a companion article together with experimental calibration procedures. Here, we examine the RD distribution in curved-faced tablets with special reference to the die wall lubrication conditions. The compaction of powders is examined using finite element analysis, which involves the following factors: constitutive behavior of powder, friction between powder and tooling, geometry of die and punches, sequence of punch motions, and initial conditions that result from die fill. The predictions of the model are validated using experimental RD maps. It is shown that different die wall lubrication conditions induce opposite density distribution trends in identical tablets (weight, height, and material). The importance of the internal tablet structure is illustrated with respect to break force, failure mode, and friability: it is demonstrated that for a given average tablet density the break force and failure mode are not unique. Also, tablet regions having lower density locally have higher propensity for damage. The applicability of finite element analysis for optimizations of formulation design, process development, tablet image, and tool design is discussed. PMID:15236453

Sinka, I C; Cunningham, J C; Zavaliangos, A

2004-08-01

294

Distribution  

Microsoft Academic Search

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

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

2006-01-01

295

Preliminary distributional analysis of US endangered bird species  

Microsoft Academic Search

A first exploration of applications of ecological niche modeling and geographic distributional prediction to endangered species protection is developed. Foci of richness of endangered bird species are identified in coastal California and along the southern fringe of the United States. Species included on the Endangered Species List on the basis of peripheral populations inflate these concentrations considerably. Species without protection

MANDALINE E. GODOWN; A. TOWNSEND PETERSON

2000-01-01

296

Metagenomic Analysis of Water Distribution System Bacterial Communities  

EPA Science Inventory

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...

297

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

EPA Science Inventory

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

298

ANALYSIS OF COARSELY GROUPED DATA FROM THE LOGNORMAL DISTRIBUTION  

EPA Science Inventory

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...

299

Analysis of distributed cooled high power millimeter wave windows  

SciTech Connect

The sectional high-frequency (100--170 GHz) distributed cooled window has been investigated both electromagnetically and thermally previously using computational electromagnetics (EM) and thermal codes. Recent data describes the relationship to some experimental data for the window. Results are presented for time domain CW EM analyses and CW thermal and stress calculations.

Nelson, S.D.; Caplan, M.; Reitter, T.A.

1995-09-09

300

Statistical sequential analysis for particle size distribution of magnetic nanoparticles  

Microsoft Academic Search

We present two statistical sequential analytical approaches to estimate particle size distribution of magnetic nanoparticles. They are termed sequential least square estimation and sequential linear minimum mean square error estimation, respectively. These approaches are implemented and quantified within the formalism of sequential estimation theory. The proposed methods are based on the data sampled sequentially in time and no matrix inversions

Gang Lei; Yanbin Li; J. Zhao; K. R. Shao

2008-01-01

301

Optimizing Distributed Practice: Theoretical Analysis and Practical Implications  

ERIC Educational Resources Information Center

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,…

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

2009-01-01

302

Analysis of the environmental benefits of Distributed Generation  

Microsoft Academic Search

The promotion of distributed generation (DG) is a direct consequence of an international drive for sustainable development and advances in technology. At present, the development of environmentally friendly (renewable energy sources) and high efficiency power generation (combined heat and power) has attracted significant attention all over the world. However, traditional supervision and management systems in the power industry prevent a

Kejun Qian; Chengke Zhou; Yue Yuan; Xiaodan Shi; Malcolm Allan

2008-01-01

303

Statistical analysis of solar measurements in Algeria using beta distributions  

Microsoft Academic Search

A method of smoothing solar data by beta probability distributions is implemented in this paper. In the first step, this method has been used to process daily sunshine duration data recorded at thirty-three meteorological stations in Algeria for eleven year periods or more. In the second step, it has been applied to hourly global solar irradiation flux measured in Algiers

F. Youcef Ettoumi; A. Mefti; A. Adane; M. Y. Bouroubi

2002-01-01

304

High Resolution PV Power Modeling for Distribution Circuit Analysis  

SciTech Connect

NREL has contracted with Clean Power Research to provide 1-minute simulation datasets of PV systems located at three high penetration distribution feeders in the service territory of Southern California Edison (SCE): Porterville, Palmdale, and Fontana, California. The resulting PV simulations will be used to separately model the electrical circuits to determine the impacts of PV on circuit operations.

Norris, B. L.; Dise, J. H.

2013-09-01

305

A novel technique for the analysis of radial distribution systems  

Microsoft Academic Search

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

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

2001-01-01

306

Bayesian Analysis of the Mass Distribution of Neutron Stars  

NASA Astrophysics Data System (ADS)

The distribution of masses for neutron stars is analyzed using the Bayesian statistical inference, evaluating the likelihood of two a priori gaussian peaks distribution by using fifty-five measured points obtained in a variety of systems. The results strongly suggest the existence of a bimodal distribution of the masses, with the first peak around 1.35M? ± 0.06M? and a much wider second peak at 1.73M? ± 0.36M?. We compared the two gaussian's model centered at 1.35M? and 1.55M? against a "single gaussian" model with 1.50M? ± 0.11M? using 3? that provided a wide peak covering objects the full range of observed of masses. In order to compare models, BIC (Baysesian Information Criterion) can be used and a strong evidence for two distributions model against one peak model was found. The results support earlier views related to the different evolutionary histories of the members for the first two peaks, which produces a natural separation (in spite that no attempt to "label" the systems has been made). However, the recently claimed low-mass group, possibly related to O - Mg - Ne core collapse events, has a monotonically decreasing likelihood and has not been identified within this sample.

Valentim, Rodolfo; Horvath, Jorge E.; Rangel, Eraldo M.

307

Distributed Detection Over Noisy Networks: Large Deviations Analysis  

Microsoft Academic Search

We study the large deviations performance of consensus+innovations distributed detection over noisy networks, where agents at a time step $k$ cooperate with their immediate neighbors (consensus) and assimilate their new observations (innovation.) We show that, under noisy communication, all agents can still achieve an exponential error rate, even when certain (or most) agents cannot detect the event of interest in

Dušan Jakovetic; José M. F. Moura; João Xavier

2012-01-01

308

Finite element analysis of stress distribution in thermal barrier coatings  

Microsoft Academic Search

A numerical simulation of crack development within APS TBC systems is presented. The TGO thickening and creep deformation of all system constituents is modelled. Two dimensional periodic unit cell is used to examine the effect of interfacial asperity on stress distribution and subsequent delamination of APS TBC. A study of cyclic loading and of creep of the base material on

Marcin Bia?as

2008-01-01

309

Probabilistic security analysis of shipboard DC zonal electrical distribution systems  

Microsoft Academic Search

Due to significant gains in terms of survivability, weight, manning, and cost obtained from DC zonal electrical distribution systems (DC ZEDS), various practical applications of DC ZEDS to shipboard electric power systems are expected in the foreseeing future. How to ensure whether shipboard DC ZEDS under different power outage events is secure becomes important for real-time operation and planning of

Chun-Lien Su; Chun-Teng Yeh

2008-01-01

310

Conduits and dike distribution analysis in San Rafael Swell, Utah  

NASA Astrophysics Data System (ADS)

Volcanic fields generally consist of scattered monogenetic volcanoes, such as cinder cones and maars. The temporal and spatial distribution of monogenetic volcanoes and probability of future activity within volcanic fields is studied with the goals of understanding the origins of these volcano groups, and forecasting potential future volcanic hazards. The subsurface magmatic plumbing systems associated with volcanic fields, however, are rarely observed or studied. Therefore, we investigated a highly eroded and exposed magmatic plumbing system on the San Rafael Swell (UT) that consists of dikes, volcano conduits and sills. San Rafael Swell is part of the Colorado Plateau and is located east of the Rocky Mountain seismic belt and the Basin and Range. The overburden thickness at the time of mafic magma intrusion (Pliocene; ca. 4 Ma) into Jurassic sandstone is estimated to be ~800 m based on paleotopographical reconstructions. Based on a geologic map by P. Delaney and colleagues, and new field research, a total of 63 conduits are mapped in this former volcanic field. The conduits each reveal features of root zone and / or lower diatremes, including rapid dike expansion, peperite and brecciated intrusive and host rocks. Recrystallized baked zone of host rock is also observed around many conduits. Most conduits are basaltic or shonkinitic with thickness of >10 m and associated with feeder dikes intruded along N-S trend joints in the host rock, whereas two conduits are syenitic and suggesting development from underlying cognate sills. Conduit distribution, which is analyzed by a kernel function method with elliptical bandwidth, illustrates a N-S elongate higher conduit density area regardless of the azimuth of closely distributed conduits alignment (nearest neighbor distance <200 m). In addition, dike density was calculated as total dike length in unit area (km/km^2). Conduit and sill distribution is concordant with the high dike density area. Especially, the distribution of conduits is not random with respect to the dike distribution with greater than 99% confidence on the basis of the Kolmogorov-Smirnov test. On the other hand, dike density at each conduits location also suggests that there is no threshold of dike density for conduit formation. In other words, conduits may be possible to develop from even short mapped dikes in low dike density areas. These results show effectiveness of studying volcanic vent distribution to infer the size of magmatic system below volcanic fields and highlight the uncertainty of forecasting the location of new monogenetic volcanoes in active fields, which may be associated with a single dike intrusion.

Kiyosugi, K.; Connor, C.; Wetmore, P. H.; Ferwerda, B. P.; Germa, A.

2011-12-01

311

Weibull statistical analysis of area effect on the breakdown strength in polymer films  

Microsoft Academic Search

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

Saeed UI-Haq; G. R. G. Raju

2002-01-01

312

Limiting exit location distributions in the stochastic exit problem  

SciTech Connect

Consider a two-dimensional continuous-time dynamical system, with an attracting fixed point S. If the deterministic dynamics are perturbed by white noise (random perturbations) of strength {epsilon}, the system state will eventually leave the domain of attraction {Omega} of S. The authors analyze the case when, as {epsilon} {yields} 0, the exit location on the boundary {partial_derivative}{Omega} is increasingly concentrated near a saddle point H of the deterministic dynamics. They show using formal methods that the asymptotic form of the exit location distribution on {partial_derivative}{Omega} is generically non-Gaussian and asymmetric, and classify the possible limiting distributions. A key role is played by a parameter {mu}, equal to the ratio {vert_bar}{lambda}{sub s}(H){vert_bar}/{lambda}{sub u}(H) of the stable and unstable eigenvalues of the linearized deterministic flow at H. If {mu} < 1, then the exit location distribution is generically asymptotic as {epsilon} {r_arrow} 0 to a Weibull distribution with shape parameter 2/{mu}, on the {Omicron}({epsilon}{sup {mu}/2}) lengthscale near H. If {mu} > 1, it is generically asymptotic to a distribution on the {Omicron}({epsilon}{sup 1/2}) lengthscale, whose moments they compute. The treatment employs both matched asymptotic expansions and stochastic analysis. As a byproduct of the treatment, the authors clarify the limitations of the traditional Eyring formula for the weak-noise exit time asymptotics.

Maier, R.S.; Stein, D.L. [Univ. of Arizona, Tucson, AZ (United States)] [Univ. of Arizona, Tucson, AZ (United States)

1997-06-01

313

Moment analysis of the probability distribution of different sandpile models  

NASA Astrophysics Data System (ADS)

We reconsider the moment analysis of the Bak-Tang-Wiesenfeld and the stochastic sandpile model introduced by Manna [J. Phys. A 24, L363 (1991)] in two and three dimensions. In contrast to recently performed investigations our analysis reveals that the models are characterized by different scaling behavior, i.e., they belong to different universality classes.

Lübeck, S.

2000-01-01

314

Flaw strength distributions and statistical parameters for ceramic fibers: The normal distribution  

NASA Astrophysics Data System (ADS)

The present paper investigates large sets of ceramic fibre failure strengths (500 to 1000 data) produced using tensile tests on tows that contained either 500 or 1000 filaments. The probability density function was determined through acoustic emission monitoring which allowed detection and counting of filament fractures. The statistical distribution of filament strengths was described using the normal distribution. The Weibull equation was then fitted to this normal distribution for estimation of statistical parameters. A perfect agreement between both distributions was obtained, and a quite negligible scatter in statistical parameters was observed, as opposed to the wide variability that is reported in the literature. Thus it was concluded that flaw strengths are distributed normally and that the statistical parameters that were derived are the true ones. In a second step, the conventional method of estimation of Weibull parameters was applied to these sets of data and, then, to subsets selected randomly. The influence of other factors involved in the conventional method of determination of statistical parameters is discussed. It is demonstrated that selection of specimens, sample size, and method of construction of so-called Weibull plots are responsible for statistical parameters variability.

R'Mili, M.; Godin, N.; Lamon, J.

2012-05-01

315

Nonlinear structural analysis on distributed-memory computers  

NASA Technical Reports Server (NTRS)

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

Watson, Brian C.; Noor, Ahmed K.

1995-01-01

316

Exploring Vector Fields with Distribution-based Streamline Analysis  

SciTech Connect

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.

Lu, Kewei; Chaudhuri, Abon; Lee, Teng-Yok; Shen, Han-Wei; Wong, Pak C.

2013-02-26

317

Diffractive parton distributions from the analysis with higher twist  

SciTech Connect

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

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

2007-12-01

318

Periodic analysis of total ozone and its vertical distribution  

NASA Technical Reports Server (NTRS)

Both total ozone and vertical distribution ozone data from the period 1957 to 1972 are analyzed. For total ozone, improved monthly zonal means for both hemispheres are computed by weighting individual station monthly means by a factor which compensates for the close grouping of stations in certain regions of latitude bands. Longitudinal variability show maxima in summer in both hemispheres, but, in winter, only in the Northern Hemisphere. The geographical distributions of the long term mean, and the annual, quasibiennial and semiannual waves in total ozone over the Northern Hemisphere are presented. The extratropical amplitude of the annual wave is by far the largest of the three, as much as 120 m atm cm over northern Siberia. There is a tendency for all three waves to have maxima in high latitudes. Monthly means of the vertical distribution of ozone determined from 3 to 8 years of ozonesonde data over North America are presented. Number density is highest in the Arctic near 18 km. The region of maximum number density slopes upward toward 10 N, where the long term mean is 45 x 10 to the 11th power molecules cm/3 near 26 km.

Wilcox, R. W.; Nastrom, G. D.; Belmont, A. D.

1975-01-01

319

Analysis of charged hadron multiplicity distributions at RHIC  

NASA Astrophysics Data System (ADS)

It is demonstrated that with Heinz's collective flow model charged particle distributions at AGS and lower SPS energies (less than 20 GeV/n), can successfully be analyzed, but that the model fails for the RHIC data. Heinz's model calculation underestimates the tails of the charged particle distributions from RHIC, the discrepancy becoming bigger as the energy increases. To study the multiplicity distributions at RHIC we develop the so-called ''Thermalization Component Model'', which is based on Heinz's collective flow model. It is realized that the limitation of phase space of collective flow can be reflected in that of the thermalization region. By comparing the contributions of particle production from the thermalization regions at different energies and different centralities, we can deepen our understanding of the features of collective motion at RHIC. Supported by Excellent Youth Foundation of Hubei Scientific Committee(2006ABB036), Education Commission of Hubei Province of China (Z20081302) and Natural Science Foundation of China Three Gorges University (2003C02)

Xiong, Wei; Feng, Sheng-Qin

2008-08-01

320

Structural reliability analysis of laminated CMC components  

NASA Technical Reports Server (NTRS)

For laminated ceramic matrix composite (CMC) materials to realize their full potential in aerospace applications, design methods and protocols are a necessity. The time independent failure response of these materials is focussed on and a reliability analysis is presented associated with the initiation of matrix cracking. A public domain computer algorithm is highlighted that was coupled with the laminate analysis of a finite element code and which serves as a design aid to analyze structural components made from laminated CMC materials. Issues relevant to the effect of the size of the component are discussed, and a parameter estimation procedure is presented. The estimation procedure allows three parameters to be calculated from a failure population that has an underlying Weibull distribution.

Duffy, Stephen F.; Palko, Joseph L.; Gyekenyesi, John P.

1991-01-01

321

Part I: porosity dependence of the Weibull modulus for hydroxyapatite and other brittle materials.  

PubMed

Porous brittle materials are used as filters, catalyst supports, solid oxide fuel cells and biomedical materials. However the literature on the Weibull modulus, m, versus volume fraction porosity, P, is extremely limited despite the importance of m as a gauge of mechanical reliability. In Part I of this study, m is determined for 441 sintered hydroxyapatite (HA) specimens fractured in biaxial flexure for 0.08 ? P ? 0.62. In this study, we analyze a combined data set collected from the literature that represents work from a total of 17 different research groups (including the present authors), eight different materials and more than 1560 oxide and non-oxide specimens, the m versus P plot is "U-shaped" with a wide band of m values for P<0.1 (Region I) and P>0.55 (Region III), and a narrower band of m values in the intermediate porosity region of 0.1, and the Young's modulus E for the HA specimens tested in Part I along with literature data for other brittle materials. Both and E are power law functions of the degree of densification, ?, where ?=1-P/P(G) and P(G) is the green (unfired) porosity. PMID:22402151

Fan, X; Case, E D; Ren, F; Shu, Y; Baumann, M J

2012-04-01

322

White Matter Changes in Primary Dystonia Determined by 2D Distribution Analysis of Diffusion Tensor Images  

PubMed Central

Purpose To determine brain tissue affected by dystonia by making group comparison of parameter-based diffusion tensor imaging (DTI) distributions of patients with control subjects. A 2D distribution analysis of mean diffusivity and fractional anisotropy index was used for modeling brain tissues according to the inherent diffusion characteristics. Materials and Methods Seven affected carriers of the DYT1 dystonia mutation and eight healthy control subjects were imaged for a previous study. We employed a 2D distribution analysis of all the diffusion voxels and a four compartmental brain model for group comparison of the dystonia subjects and controls. Results Our analysis showed disease involvement in the white matter of the patients. Excellent tissue characterization was achieved automatically using the 2D distribution analysis based on a physical brain model. Conclusion This 2D analysis implicated white matter in dystonia and could be useful as a screening tool in diseases with unknown pathologies.

Vo, An; Eidelberg, David; Ulug, Aziz M.

2014-01-01

323

Distributed Multiscale Data Analysis and Processing for Sensor Networks.  

National Technical Information Service (NTIS)

While multiresolution data analysis, processing, and compression hold considerable promise for sensor network applications, progress has been confounded by two factors. First, typical sensor data are irregularly spaced, which is incompatible with standard...

H. Choi R. Baraniuk R. Wagner S. Sarvotham

2005-01-01

324

GSM-Distributed RTK for Precise Analysis of Speed Skiing  

Microsoft Academic Search

The applications to dynamic sports for an accurate analysis of trajectories represent a new perspective for carrier phase-based GPS positioning. Introduced in competitive skiing, the GPS technique provides all the qualitative data for a complete analysis of position\\/velocity\\/acceleration so that the measured trajectories can be compared throughout the entire track. Consequently, it can help the athletes to find the fastest

J. Skaloud; H. Gontran; B. Merminod

2004-01-01

325

Analysis of distributed control systems with shared communication and computation resources  

Microsoft Academic Search

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

Payam Naghshtabrizi; Joao P. Hespanha

2009-01-01

326

Groundwork for Integrated Analysis of Distributed S3C Data  

NASA Astrophysics Data System (ADS)

We present a vision for the evolution of existing and future NASA Sun Solar System Connection (S3C) data resources into an integrated data analysis environment. Focusing first on the time-series datasets typical of in- situ measurements, we describe an architecture designed to overcome the traditional barriers to integrated analysis, namely data access and format variations. We are building a groundwork layer on top of which it will be possible to construct common science libraries for plotting and analysis, very similar to the common set of image processing tools developed within the Solar community (for which the data format problem is greatly simplified due to the nearly universal use of FITS). The core of our approach is the use of a set internal data models, one for each type of in-situ science data. We present preliminary versions of the data models for comment. Furthermore, the areas in which data model design have a significant impact on science analysis capabilities will be discussed. The approach presented here is currently deployed in the DataShop analysis tool (http://sd-www.jhuapl.edu/datashop) and is also planned for use in the Virtual Heliospheric Observatory (VHO, http://vho.nasa.gov) and the Virtual Space Physics Observatory (VSPO, http://vspo.gsfc.nasa.gov).

Vandegriff, J.; Roberts, A.; Szabo, A.

2006-05-01

327

Multi-species analysis of ion distributions at Mars  

NASA Astrophysics Data System (ADS)

This study focuses on using the Mars Test Particle simulation to compare observations with virtual detections of O+, O2+, CO2+, and H+ in an orbital configuration in the Mars space environment. These planetary pick-up ions are formed when the solar wind directly interacts with the neutral atmosphere, causing the ions to be accelerated by the background convective electric field. The subsequent mass loading and ion escape are still the subject of great interest, specifically with respect to which species dominates ion loss from Mars. Modeling efforts and observations have found different results; some conclude that O+ is the most dominant escaping ion while others conclude that O2+ has the larger total loss rate. Furthermore, mass loss might actually favor CO2+ because of its tri-atomic structure. To address this unresolved issue, this study will present velocity space distributions for different species and discuss fluxes and escape rates using different modeling parameters. The simulation will also illustrate individual particle traces, which reveal the origin and trajectories of the different ion species. Finally, results from different solar conditions will be presented with respect to ion fluxes and energies as well as overall escape in order to robustly describe the physical processes controlling planetary ion distributions and atmospheric escape.

Curry, S.; Liemohn, M. W.; Fang, X.; Ma, Y.; Johnson, B.; Bougher, S. W.; Dong, C.

2012-12-01

328

Analysis of an algorithm for distributed recognition and accountability  

SciTech Connect

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

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

1993-08-01

329

Visualization and analysis of lipopolysaccharide distribution in binary phospholipid bilayers  

SciTech Connect

Lipopolysaccharide (LPS) is an endotoxin released from the outer membrane of Gram-negative bacteria during infections. It have been reported that LPS may play a role in the outer membrane of bacteria similar to that of cholesterol in eukaryotic plasma membranes. In this article we compare the effect of introducing LPS or cholesterol in liposomes made of dipalmitoylphosphatidylcholine/dioleoylphosphatidylcholine on the solubilization process by Triton X-100. The results show that liposomes containing LPS or cholesterol are more resistant to solubilization by Triton X-100 than the binary phospholipid mixtures at 4 {sup o}C. The LPS distribution was analyzed on GUVs of DPPC:DOPC using FITC-LPS. Solid and liquid-crystalline domains were visualized labeling the GUVs with LAURDAN and GP images were acquired using a two-photon microscope. The images show a selective distribution of LPS in gel domains. Our results support the hypothesis that LPS could aggregate and concentrate selectively in biological membranes providing a mechanism to bring together several components of the LPS-sensing machinery.

Henning, Maria Florencia [Instituto de Investigaciones Bioquimicas La Plata (INIBIOLP), CCT-La Plata, CONICET, Facultad de Ciencias Medicas, UNLP, Calles 60 y 120, 1900 La Plata (Argentina)] [Instituto de Investigaciones Bioquimicas La Plata (INIBIOLP), CCT-La Plata, CONICET, Facultad de Ciencias Medicas, UNLP, Calles 60 y 120, 1900 La Plata (Argentina); Sanchez, Susana [Laboratory for Fluorescence Dynamics, University of California-Irvine, Irvine, CA (United States)] [Laboratory for Fluorescence Dynamics, University of California-Irvine, Irvine, CA (United States); Bakas, Laura, E-mail: lbakas@biol.unlp.edu.ar [Instituto de Investigaciones Bioquimicas La Plata (INIBIOLP), CCT-La Plata, CONICET, Facultad de Ciencias Medicas, UNLP, Calles 60 y 120, 1900 La Plata (Argentina) [Instituto de Investigaciones Bioquimicas La Plata (INIBIOLP), CCT-La Plata, CONICET, Facultad de Ciencias Medicas, UNLP, Calles 60 y 120, 1900 La Plata (Argentina); Departamento de Ciencias Biologicas, Facultad de Ciencias Exactas, UNLP, Calles 47 y 115, 1900 La Plata (Argentina)

2009-05-22

330

The analysis of biodiversity using rank abundance distributions.  

PubMed

Biodiversity is an important topic of ecological research. A common form of data collected to investigate patterns of biodiversity is the number of individuals of each species at a series of locations. These data contain information on the number of individuals (abundance), the number of species (richness), and the relative proportion of each species within the sampled assemblage (evenness). If there are enough sampled locations across an environmental gradient then the data should contain information on how these three attributes of biodiversity change over gradients. We show that the rank abundance distribution (RAD) representation of the data provides a convenient method for quantifying these three attributes constituting biodiversity. We present a statistical framework for modeling RADs and allow their multivariate distribution to vary according to environmental gradients. The method relies on three models: a negative binomial model, a truncated negative binomial model, and a novel model based on a modified Dirichlet-multinomial that allows for a particular type of heterogeneity observed in RAD data. The method is motivated by, and applied to, a large-scale marine survey off the coast of Western Australia, Australia. It provides a rich description of biodiversity and how it changes with environmental conditions. PMID:19432789

Foster, Scott D; Dunstan, Piers K

2010-03-01

331

Cluster analysis of roadside ultrafine particle size distributions  

NASA Astrophysics Data System (ADS)

This study reports the diurnal, seasonal, and annual variation of ultrafine particle size distributions in downtown Toronto. The k-means clustering algorithm was applied to five years of size-resolved data for particles with diameters less than 100 nm. Continuous particle number concentrations were measured 16 m from a major arterial roadway between March 2006 and May 2011 using a Fast Mobility Particle Sizer. Eight particle size distribution (PSD) types were identified. The PSD types exhibited distinct weekday-weekend and diurnal patterns. The relative frequency that each PSD occurred varied with season and wind direction and was correlated with other pollutants. These temporal patterns and correlation helped in elucidating the sources and processes that each of the eight PSD represent. Finally, similar PSD types were observed in residential areas located 6 and 15 km away from the central monitoring site suggesting that these PSD types may be generalizable to other sites. Identification of PSD types was found to be a valuable tool to support the interpretation of PSD data so as to elucidate the sources and processes contributing to ultrafine particle concentrations.

Sabaliauskas, Kelly; Jeong, Cheol-Heon; Yao, Xiaohong; Jun, Yun-Seok; Evans, Greg

2013-05-01

332

A data analysis expert system for large established distributed databases  

NASA Technical Reports Server (NTRS)

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.

Gnacek, Anne-Marie; An, Y. Kim; Ryan, J. Patrick

1987-01-01

333

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

Microsoft Academic Search

This paper deals with analysis of statistical properties of multi-look processed polarimetric SAR data. Based on an assumption that the multi-look polarimetric measurement is a product between a Gamma-distributed texture variable and a Wishart-distributed polarimetric speckle variable, it is shown that the multi-look polarimetric measurement from a nonhomogeneous region obeys a generalized K-distribution. In order to validate this statistical model,

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

1995-01-01

334

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

Microsoft Academic Search

This study provides a step-wise analysis of a conceptual grid-based distributed rainfall-runoff model, the United States National Weather Service (US NWS) Hydrology Laboratory Research Distributed Hydrologic Model (HL-RDHM). It evaluates model parameter sensitivities for annual, monthly, and event time periods with the intent of elucidating the key parameters impacting the distributed model's forecasts. This study demonstrates a methodology that balances

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

2007-01-01

335

Dynamic Condor-based Services for Distributed Image Analysis  

Microsoft Academic Search

Interactive image processing is an important requirement in many industrial applications, such as the inspection of industrial parts within a manufacturing environment, or the processing of images from surveillance cameras. Being able to achieve this quickly and accurately is often essential for the success of such industrial applications. A service-based approach that autonomously launches Image Analysis Services (accessible through a

Simon Caton; Omer F. Rana; Bruce Batchelor

2007-01-01

336

Geostatistical analysis of China inbound tourism spatial distribution structure  

Microsoft Academic Search

As an important method of GIS-based spatial analysis, geostatistics has been applied in a variety of scientific disciplines, which has expanded from natural phenomena to some socio-economic problems (metropolitan house price, land price), for its special power to reveal the spatial characteristics, structure and process of regionalized variables. China inbound tourism phenomenon can also be taken as regionalized variable as

Fajian Liu; Jie Zhang; Jinhe Zhang; Yawen Zhu; Dongdong Chen

2010-01-01

337

A Distributed Flocking Approach for Information Stream Clustering Analysis  

Microsoft Academic Search

Intelligence analysts are currently overwhelmed with the amount of information streams generated everyday. There is a lack of comprehensive tool that can real-time analyze the information streams. Document clustering analysis plays an important role in improving the accuracy of information retrieval. However, most clustering technologies can only be applied for analyzing the static document collection because they normally require a

Xiaohui Cui; Thomas E. Potok

2006-01-01

338

Temporal Distributions of Problem Behavior Based on Scatter Plot Analysis.  

ERIC Educational Resources Information Center

A large-scale analysis was conducted of problem behavior by observing 20 individuals living in residential facilities. Data were converted into scatter plot formats. When the data were transformed into aggregate "control charts," 12 of 15 sets of data revealed 30-minute intervals during which problem behavior was more likely to occur. (Author/CR)

Kahng, SungWoo; Iwata, Brian A.; Fischer, Sonya M.; Page, Terry J.; Treadwell, Kimberli R. H.; Williams, Don E.; Smith, Richard G.

1998-01-01

339

Sensitivity Analysis of Distributed Soil Moisture Profiles by Active Distributed Temperature Sensing  

NASA Astrophysics Data System (ADS)

Monitoring and measuring the fluctuations of soil moisture at large scales in the filed remains a challenge. Although sensors based on measurement of dielectric properties such as Time Domain Reflectometers (TDR) and capacity-based probes can guarantee reasonable responses, they always operate on limited spatial ranges. On the other hand optical fibers, attached to a Distribute Temperature Sensing (DTS) system, can allow for high precision soil temperature measurements over distances of kilometers. A recently developed technique called Active DTS (ADTS) and consisting of a heat pulse of a certain duration and power along the metal sheath covering the optical fiber buried in the soil, has proven a promising alternative to spatially-limited probes. Two approaches have been investigated to infer distributed soil moisture profiles in the region surrounding the optic fiber cable by analyzing the temperature variations during the heating and the cooling phases. One directly relates the change of temperature to the soil moisture (independently measured) to develop specific calibration curve for the soil used; the other requires inferring the thermal properties and then obtaining the soil moisture by inversion of known relationships. To test and compare the two approaches over a broad range of saturation conditions a large lysimeter has been homogeneously filled with loamy soil and 52 meters of fiber optic cable have been buried in the shallower 0.8 meters in a double coil rigid structure of 15 loops along with a series of capacity-based sensors (calibrated for the soil used) to provide independent soil moisture measurements at the same depths of the optical fiber. Thermocouples have also been wrapped around the fiber to investigate the effects of the insulating cover surrounding the cable, and in between each layer in order to monitor heat diffusion at several centimeters. A high performance DTS has been used to measure the temperature along the fiber optic cable. Several soil moisture profiles have been generated in the lysimeter either varying the water table height or by wetting the soil from the top. The sensitivity of the ADTS method for heat pulses of different duration and power and ranges of spatial and temporal resolution are presented.

Ciocca, F.; Van De Giesen, N.; Assouline, S.; Huwald, H.; Lunati, I.

2012-12-01

340

Application of digital image analysis for size distribution measurements of microbubbles.  

National Technical Information Service (NTIS)

This work employs digital image analysis to measure the size distribution of microbubbles generated by the process of electroflotation for use in solid/liquid separation processes. Microbubbles are used for separations in the mineral processing industry a...

S. E. Burns S. Yiacoumi D. Frost C. Tsouris

1997-01-01

341

Instrumental Neutron Activation Analysis in the Measurement of Trace Element Distribution at Two Coal Conversion Plants.  

National Technical Information Service (NTIS)

Instrumental neutron activation analysis was used to study the elemental concentration in the complex materials produced by the H-Coal process and the low Btu gasification process at the University of Minnesota at Duluth (UMD). Trace element distribution ...

L. M. Roseberry F. F. Dyer

1984-01-01

342

Thermal analysis of soft magnetic composite motors using a hybrid model with distributed heat sources  

Microsoft Academic Search

This paper presents a hybrid thermal model with distributed heat sources for thermal analysis of soft magnetic composite (SMC) motors. The model uses a combination of lumped and distributed thermal parameters, which can be obtained from motor dimensions and thermal constants. The model can be used to calculate the core loss in each part, in combination with three-dimensional magnetic field

Youguang Guo; Jian Guo Zhu; Wei Wu

2005-01-01

343

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

SciTech Connect

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

Not Available

1991-08-01

344

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

SciTech Connect

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

Sihombing, P.

1991-08-20

345

Numerical Analysis of Temperature Distribution in Friction Welding of Carbon Steel  

Microsoft Academic Search

The purpose of this study is to estimate temperature distribution in the vicinity of weld interface during a friction welding process involving an upset process. On the base of a simple model of friction heat input, a non-steady heat conduction analysis was carried out by finite element method. As a result from a comparison of the estimated temperature distribution with

Yoshihiro Isshiki; Hiroshi Yamaguchi; Gosaku Kawai; Koichi Ogawa

2007-01-01

346

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

Microsoft Academic Search

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

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

2010-01-01

347

Analysis of disc brake temperature distribution during single braking under non-axisymmetric load  

Microsoft Academic Search

This paper aims to study and compare the temperature distributions caused by mutual sliding of two members of the disc brake system basing on two- and three-dimensional FE modelling techniques and complexity of the phenomenon. First step of the analysis based on the previously developed model where the intensity of heat flux was assumed to be uniformly distributed on the

Adam Adamowicz; Piotr Grzes

2011-01-01

348

A pair distribution function analysis of zeolite beta  

SciTech Connect

We describe the structural refinement of zeolite beta using the local structure obtained with the pair distribution function (PDF) method. A high quality synchrotron and two neutron scattering datasets were obtained on two samples of siliceous zeolite beta. The two polytypes that make up zeolite beta have the same local structure; therefore refinement of the two structures was possible using the same experimental PDF. Optimized structures of polytypes A and B were used to refine the structures using the program PDFfit. Refinements using only the synchrotron or the neutron datasets gave results inconsistent with each other but a cyclic refinement with the two datasets gave a good fit to both PDFs. The results show that the PDF method is a viable technique to analyze the local structure of disordered zeolites. However, given the complexity of most zeolite frameworks, the use of both X-ray and neutron radiation and high-resolution patterns is essential to obtain reliable refinements.

Martinez-Inesta, M.M.; Peral, I.; Proffen, T.; Lobo, R.F. (Delaware); (LANL)

2010-07-20

349

An analysis of the Seasat Satellite Data Distribution System  

NASA Technical Reports Server (NTRS)

A computerized data distribution network for remote accessing of Seasat generated data is described. The service is intended as an experiment to determine user needs and operational abilities for utilizing on-line satellite generated oceanographic data. Synoptic weather observations are input to the U.S. Fleet Numerical Oceanographic Central for preparation and transfer to a PDP 11/60 central computer, from which all access trunks originate. The data available includes meteorological and sea-state information in the form of analyses and forecasts, and users are being monitored for reactions to the system design, data products, system operation, and performance evaluation. The system provides data on sea level and upper atmospheric pressure, sea surface temperature, wind magnitude and direction, significant wave heights, direction, and periods, and spectral wave data. Transmissions have a maximum rate of 1.1 kbit/sec over the telephone line.

Ferrari, A. J.; Renfrow, J. T.

1980-01-01

350

Analysis of phase distribution phenomena in microgravity environments  

NASA Technical Reports Server (NTRS)

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.

Lahey, Richard, Jr.; Bonetto, Fabian

1994-01-01

351

Southern Arizona riparian habitat: Spatial distribution and analysis  

NASA Technical Reports Server (NTRS)

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.

Lacey, J. R.; Ogden, P. R.; Foster, K. E.

1975-01-01

352

A comparison of six statistical distributions for analysis of chromosome aberration data for radiation biodosimetry.  

PubMed

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

Ainsbury, Elizabeth A; Vinnikov, Volodymyr A; Maznyk, Nataliya A; Lloyd, David C; Rothkamm, Kai

2013-07-01

353

Photoelastic analysis of stress distribution with different implant systems.  

PubMed

The aim of this study was to evaluate stress distribution with different implant systems through photoelasticity. Five models were fabricated with photoelastic resin PL-2. Each model was composed of a block of photoelastic resin (10 × 40 × 45 mm) with an implant and a healing abutment: model 1, internal hexagon implant (4.0 × 10 mm; Conect AR, Conexão, São Paulo, Brazil); model 2, Morse taper/internal octagon implant (4.1 × 10 mm; Standard, Straumann ITI, Andover, Mass); model 3, Morse taper implant (4.0 × 10 mm; AR Morse, Conexão); model 4, locking taper implant (4.0 × 11 mm; Bicon, Boston, Mass); model 5, external hexagon implant (4.0 × 10 mm; Master Screw, Conexão). Axial and oblique load (45°) of 150 N were applied by a universal testing machine (EMIC-DL 3000), and a circular polariscope was used to visualize the stress. The results were photographed and analyzed qualitatively using Adobe Photoshop software. For the axial load, the greatest stress concentration was exhibited in the cervical and apical thirds. However, the highest number of isochromatic fringes was observed in the implant apex and in the cervical adjacent to the load direction in all models for the oblique load. Model 2 (Morse taper, internal octagon, Straumann ITI) presented the lowest stress concentration, while model 5 (external hexagon, Master Screw, Conexão) exhibited the greatest stress. It was concluded that Morse taper implants presented a more favorable stress distribution among the test groups. The external hexagon implant showed the highest stress concentration. Oblique load generated the highest stress in all models analyzed. PMID:22208909

Pellizzer, Eduardo Piza; Carli, Rafael Imai; Falcón-Antenucci, Rosse Mary; Verri, Fellippo Ramos; Goiato, Marcelo Coelho; Villa, Luiz Marcelo Ribeiro

2014-04-01

354

Mechanistic information from analysis of molecular weight distributions of starch.  

PubMed

A methodology is developed for interpreting the molecular weight distributions of debranched amylopectin, based on techniques developed for quantitatively and qualitatively finding mechanistic information from the molecular weight distributions of synthetic polymers. If the only events occurring are random chain growth and stoppage (i.e., the rates are independent of degree of polymerization over the range in question), then the number of chains of degree of polymerization N, P(N), is linear in ln P(N) with a negative slope, where the slope gives the ratio of the stoppage and growth rates. This starting point suggests that mechanistic inferences can be made from a plot of lnP against N. Application to capillary electrophoresis data for the P(N) of debranched starch from across the major taxa, from bacteria (Escherichia coli), green algae (Chlamydomonas reinhardtii), mammals (Bos), and flowering plants (Oryza sativa, rice; Zea mays, maize; Triticum aestivum, wheat; Hordeum vulgare, barley; and Solanum tuberosum, potato), gives insights into the biosynthetic pathways, showing the differences and similarities of the alpha-1,4-glucans produced by the various species. Four characteristic regions for storage starch from the higher plants are revealed: (1) an initial increasing region corresponding to the formation of new branches, (2) a linear ln P region with negative slope, indicating random growth and stoppage, (3) a region corresponding to the formation of the crystalline lamellae and subsequent elongation of chains, and (4) a second linear ln P with negative slope region. Each region can be assigned to specific enzymatic processes in starch synthesis, including determining the ranges of degrees of polymerization which are subject to random and nonrandom processes. PMID:16004469

Castro, Jeffrey V; Dumas, Céline; Chiou, Herbert; Fitzgerald, Melissa A; Gilbert, Robert G

2005-01-01

355

Advanced analysis of metal distributions in human hair  

SciTech Connect

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

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

2008-06-09

356

Analysis of electron temperature distribution by Kinetic modeling of electron energy distribution function in JAEA 10 ampere negative ion source  

NASA Astrophysics Data System (ADS)

In large negative ion sources of the neutral beam injector (NBI) for large fusion devices, such as ITER and JT-60SA, one of issues is that negative ion beam might be partially intercepted at acceleration grids due to a spatial non-uniformity of negative ion production on large extraction area. Previous experiments have shown that fast electrons emitted from filament cathodes are transported in a longitudinal direction by B × grad B drift and the spatial distribution of electron temperature (Te) is strongly related with the non-uniformity of negative ion production. In this study, a three-dimensional electron transport analysis code including detailed collision processes has been developed to clarify a physical mechanism of non-uniform Te distribution. Electron density and temperature in the analysis agree well with measurements by Langmuir probe in the JAEA 10A ion source. Then, this study has clarified that the non-uniformity of Te distribution is mainly caused by the following reasons; i) fast electrons drifted in the longitudinal direction survive near the end wall with high energy up to E = 25 - 60 eV and ii) they produce thermal electrons by collision with plasma particles there.

Shibata, T.; Terasaki, R.; Kashiwagi, M.; Inoue, T.; Dairaku, M.; Taniguchi, M.; Tobari, H.; Umeda, N.; Watanabe, K.; Sakamto, K.; Hatayama, A.

2013-02-01

357

Solving Electrical Distribution Problems Using Hybrid Evolutionary Data Analysis Techniques  

Microsoft Academic Search

Abstract. Real-world electrical engineering problems can take advantage of the last Data Analysis methodologies. In this paper we will show that Genetic Fuzzy Rule-Based Systems and Genetic Programming,techniques are good choices for tackling with some,practical modeling,problems. We claim that both evolutionary processes may produce good numerical results while providing us with a model,that can be interpreted by a human,being. We

Oscar Cordón; Francisco Herrera; Luciano Sánchez

1999-01-01

358

Power systems analysis for direct current (dc) distribution systems  

SciTech Connect

Many standards, guidelines, etc., currently exist which provide guidance for dc power systems analysis. These documents are scattered throughout the industry (i.e., IEEE, UL, NEMA, GE, etc.), and primarily treat the subject as though hand calculations are being performed. It is the intent of this paper to provide guidance for performing computer aided dc power systems analyzes. This paper will cover load flow/voltage drop and short circuit calculations.

Fleischer, K. [Public Service Electric and Gas, Hancock`s Bridge, NJ (United States). Salem Nuclear Generating Station] [Public Service Electric and Gas, Hancock`s Bridge, NJ (United States). Salem Nuclear Generating Station; Munnings, R.S. [VECTRA Technologies, Inc., Lincolnshire, IL (United States)] [VECTRA Technologies, Inc., Lincolnshire, IL (United States)

1996-09-01

359

Distributed finite element analysis using a transputer network  

NASA Technical Reports Server (NTRS)

The principal objective of this research effort was to demonstrate the extraordinarily cost effective acceleration of finite element structural analysis problems using a transputer-based parallel processing network. This objective was accomplished in the form of a commercially viable parallel processing workstation. The workstation is a desktop size, low-maintenance computing unit capable of supercomputer performance yet costs two orders of magnitude less. To achieve the principal research objective, a transputer based structural analysis workstation termed XPFEM was implemented with linear static structural analysis capabilities resembling commercially available NASTRAN. Finite element model files, generated using the on-line preprocessing module or external preprocessing packages, are downloaded to a network of 32 transputers for accelerated solution. The system currently executes at about one third Cray X-MP24 speed but additional acceleration appears likely. For the NASA selected demonstration problem of a Space Shuttle main engine turbine blade model with about 1500 nodes and 4500 independent degrees of freedom, the Cray X-MP24 required 23.9 seconds to obtain a solution while the transputer network, operated from an IBM PC-AT compatible host computer, required 71.7 seconds. Consequently, the $80,000 transputer network demonstrated a cost-performance ratio about 60 times better than the $15,000,000 Cray X-MP24 system.

Watson, James; Favenesi, James; Danial, Albert; Tombrello, Joseph; Yang, Dabby; Reynolds, Brian; Turrentine, Ronald; Shephard, Mark; Baehmann, Peggy

1989-01-01

360

Making distributed ALICE analysis simple using the GRID plug-in  

NASA Astrophysics Data System (ADS)

We have developed an interface within the ALICE analysis framework that allows transparent usage of the experiment's distributed resources. This analysis plug-in makes it possible to configure back-end specific parameters from a single interface and to run with no change the same custom user analysis in many computing environments, from local workstations to PROOF clusters or GRID resources. The tool is used now extensively in the ALICE collaboration for both end-user analysis and large scale productions.

Gheata, A.; Gheata, M.

2012-06-01

361

CARES/LIFE Ceramics Analysis and Reliability Evaluation of Structures Life Prediction Program  

NASA Technical Reports Server (NTRS)

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.

Nemeth, Noel N.; Powers, Lynn M.; Janosik, Lesley A.; Gyekenyesi, John P.

2003-01-01

362

Scaling invariant distributions of firms’ exit in OECD countries  

NASA Astrophysics Data System (ADS)

Self-similar models are largely used to describe the extinction rate of biological species. In this paper we analyse the extinction rate of firms in eight OECD countries. Firms are classified by industrial sectors and sizes. We find that while a power-law distribution with exponent close to 2 fits the extinction rate very well by sector, a Weibull distribution is more appropriate if one analyses the firms’ size.

Guilmi, Corrado Di; Gallegati, Mauro; Ormerod, Paul

2004-03-01

363

Independent Orbiter Assessment (IOA): Analysis of the Electrical Power Distribution and Control Subsystem, Volume 2  

NASA Technical Reports Server (NTRS)

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.

Schmeckpeper, K. R.

1987-01-01

364

Electron density distribution analysis for some nitrated cubanes  

SciTech Connect

The investigators performed SCF molecular orbital calculations at fixed geometries for cubane, nitrocubane (NC), and 1,2-dinitrocubane (DNC) using the 3-21G basis set. Electron density distributions were then calculated from the approximate wavefunctions and subjected to various analyses. Fixed geometries and the small 3-21G basis set were used for reasons of comparison and economy. While these constraints limit the quantitative usefulness of the results, the investigators hope qualitative trends will be faithfully revealed. In all cases carbon-carbon and carbon-hydrogen bond lengths are 1.572 A and 1.076 A, respectively, and bond angles in the cubyl moiety were those of cubane. Carbon-nitrogen bonds and nitrogen-oxygen bonds were fixed at 1.44 A and 1.22 A, respectively, and the carbon-nitrogen-oxygen bond angles were set at 114.0/sup 0/. In all cases the C-N bond lies along a body diagonal. In NC, symmetry group C/sub s/, the plane of the nitro group is in the symmetry plane. In DNC, symmetry group C/sub 2/, the planes of the nitro groups are canted 45/sup 0/ from a planar arrangement. 3 refs.

Ritchie, J.P.

1985-01-01

365

Hint of polar distribution in calcium channels under PIXE analysis.  

PubMed

Pollen tubes ofLilium longiflorum were treated for 10-30 min with 10(-5) M CoCl2, which binds to calcium channels in the plasma membrane and blocks them. Cobalt analyses were performed with the Heidelberg proton microprobe, using 3 MeV protons, a beam current of about 200 pA, and a spot size of 3×5 ?m(2). X-ray spectra revealed that coblat has much higher concentrations in the cell than in the surrounding dried medium. The line scans, taken along the longitudinal cell axis in 1-?m steps, showed a cobalt gradient similar to the calcium gradient of the same cell. Based on our findings, we can conclude that neither do the cobalt signals come from the cell wall nor is the cobalt exclusively bound to the intracellular calcium-binding sites. There-fore, the present results suggest a polar distribution in calcium channels in the plasma membrane of pollen tubes. PMID:24254671

Reiss, H D; Traxel, K

1987-08-01

366

Motion synthesis and force distribution analysis for a biped robot.  

PubMed

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

Trojnacki, Maciej T; Zieli?ska, Teresa

2011-01-01

367

Development of distribution system reliability and risk analysis models  

NASA Astrophysics Data System (ADS)

The two reliability models, their testing, and the modifications of a unified distribution planning model to calculate reliability indices are described. The historical reliability assessment model HISRAM is designed to suit most utilities. Four implementation levels with different input data requirements and output capabilities permit a utility to select a level appropriate to its needs. User-defined divisions, causes and output options further add to the program flexibility. A unique feature of HISRAM is the program generation of the appropriate outage reporting form following level selection and initialization. This allows the engineer to review data input requirements before field implementation. It has the capability of estimating component failure rates and restoration times upon provision of suitable input data. The predictive reliability assessment model PRAM uses continuity criteria, together with component failure rates and restoration times to calculate load point indices. System indices similar to those produced by HISRAM are also calculated. Varying degrees of detail for representing the protection system are available through three user-selected models. Both models were tested through application. The conclusions and recommendations of the entire project are included.

Vismor, T. D.; Northcote-Green, J. E. D.; Kostyal, S. J.; Brooks, C. L.

1981-08-01

368

An empirical analysis of the distribution of overshoots in a stationary Gaussian stochastic process  

NASA Technical Reports Server (NTRS)

The frequency distribution of overshoots in a stationary Gaussian stochastic process is analyzed. The primary processes involved in this analysis are computer simulation and statistical estimation. Computer simulation is used to simulate stationary Gaussian stochastic processes that have selected autocorrelation functions. An analysis of the simulation results reveals a frequency distribution for overshoots with a functional dependence on the mean and variance of the process. Statistical estimation is then used to estimate the mean and variance of a process. It is shown that for an autocorrelation function, the mean and the variance for the number of overshoots, a frequency distribution for overshoots can be estimated.

Carter, M. C.; Madison, M. W.

1973-01-01

369

Husimi distribution and phase-space analysis of a Dicke-model quantum phase transition  

NASA Astrophysics Data System (ADS)

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 is done using two frameworks: a numerical treatment and an analytical variational approximation. Additionally, we propose a characterization of the Dicke model quantum phase transition by means of the zeros of the Husimi distribution in the variational approach.

Romera, E.; del Real, R.; Calixto, M.

2012-05-01

370

Distributed representation as a principle for the analysis of cockpit information displays.  

PubMed

This article examines the representational properties of cockpit information displays from the perspective of distributed representations (Zhang & Norman, 1994). The basic idea is that the information needed for many tasks in a cockpit is distributed across the external information displays in the cockpit and the internal minds of the pilots. It is proposed that the relative distribution of internal and external information is the major factor of a display's representational efficiency. Several functionally equivalent but representationally different navigation displays are selected to illustrate how the principle of distributed representations is applied to the analysis of the representational efficiencies of cockpit information displays. PMID:11541073

Zhang, J

1997-01-01

371

Impact analysis of automotive structures with distributed smart material systems  

NASA Astrophysics Data System (ADS)

New class of automobiles has structural skins that are quite different from their current designs. Particularly, new families of composite skins are developed with new injection molding processes. These skins while support the concept of lighter vehicles of the future, are also susceptible to damage upon impact. It is important that their design should be based on a better understanding on the type of impact loads and the resulting strains and damage. It is possible that these skins can be integrally designed with active materials to counter damages. This paper presents a preliminary analysis of a new class of automotive skins, using piezoceramic as a smart material. The main objective is to consider the complex system with, the skin to be modeled as a layered plate structure involving a lightweight material with foam and active materials imbedded on them. To begin with a cantilever beam structure is subjected to a load through piezoceramic and the resulting strain at the active material site is predicted accounting for the material properties, piezoceramic thickness, adhesive thickness including the effect of adhesives. A finite element analysis is carried out to compare experimental work. Further work in this direction would provide an analytical tool that will provide the basis for algorithms to predict and counter impacts on the future class of automobiles.

Peelamedu, Saravanan M.; Naganathan, Ganapathy; Buckley, Stephen J.

1999-06-01

372

Wavelet analysis of baryon acoustic structures in the galaxy distribution  

NASA Astrophysics Data System (ADS)

Context. Baryon acoustic oscillations (BAO) are imprinted in the density field by acoustic waves travelling in the plasma of the early universe. Their fixed scale can be used as a standard ruler to study the geometry of the universe. Aims: The BAO have been previously detected using correlation functions and power spectra of the galaxy distribution. We present a new method to detect the real-space structures associated with BAO. These baryon acoustic structures are spherical shells of relatively small density contrast, surrounding high density central regions. Methods: We design a specific wavelet adapted to search for shells, and exploit the physics of the process by making use of two different mass tracers, introducing a specific statistic to detect the BAO features. We show the effect of the BAO signal in this new statistic when applied to the ? - cold dark matter (?CDM) model, using an analytical approximation to the transfer function. We confirm the reliability and stability of our method by using cosmological N-body simulations from the MareNostrum Institut de Ciències de l'Espai (MICE). Results: We apply our method to the detection of BAO in a galaxy sample drawn from the Sloan Digital Sky Survey (SDSS). We use the "main" catalogue to trace the shells, and the luminous red galaxies (LRG) as tracers of the high density central regions. Using this new method, we detect, with a high significance, that the LRG in our sample are preferentially located close to the centres of shell-like structures in the density field, with characteristics similar to those expected from BAO. We show that stacking selected shells, we can find their characteristic density profile. Conclusions: We delineate a new feature of the cosmic web, the BAO shells. As these are real spatial structures, the BAO phenomenon can be studied in detail by examining those shells. Full Table 1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/542/A34

Arnalte-Mur, P.; Labatie, A.; Clerc, N.; Martínez, V. J.; Starck, J.-L.; Lachièze-Rey, M.; Saar, E.; Paredes, S.

2012-06-01

373

Numerical analysis of atomic density distribution in arc driven negative ion sources.  

PubMed

The purpose of this study is to calculate atomic (H(0)) density distribution in JAEA 10 ampere negative ion source. A collisional radiative model is developed for the calculation of the H(0) density distribution. The non-equilibrium feature of the electron energy distribution function (EEDF), which mainly determines the H(0) production rate, is included by substituting the EEDF calculated from 3D electron transport analysis. In this paper, the H(0) production rate, the ionization rate, and the density distribution in the source chamber are calculated. In the region where high energy electrons exist, the H(0) production and the ionization are enhanced. The calculated H(0) density distribution without the effect of the H(0) transport is relatively small in the upper region. In the next step, the effect should be taken into account to obtain more realistic H(0) distribution. PMID:24593565

Yamamoto, T; Shibata, T; Kashiwagi, M; Hatayama, A; Sawada, K; Hanada, M

2014-02-01

374

Sensitivity analysis of voltage imbalance in distribution networks with rooftop PVs  

Microsoft Academic Search

A comprehensive voltage imbalance sensitivity analysis and stochastic evaluation based on the rating and location of single-phase grid-connected rooftop photovoltaic cells (PVs) in a residential low voltage distribution network are presented. The voltage imbalance at different locations along a feeder is investigated. In addition, the sensitivity analysis is performed for voltage imbalance in one feeder when PVs are installed in

Farhad Shahnia; Ritwik Majumder; Arindam Ghosh; Gerard Ledwich; Firuz Zare

2010-01-01

375

Continuous Extensions of Matrix Formulations in Correspondence Analysis, with Applications to the FGM Family of Distributions  

Microsoft Academic Search

Correspondence analysis is a multivariate technique used to visualizecategorical data, usually data in a two-way contingency table. Someextensions of correspondence analysis to a continuous bivariate distributionare presented, firstly from a canonical correlation analysisperspective and then from a continuous scaling perspective. These extensionsare applied to the Farlie-Gumbel-Morgenstern (FGM) familyof bivariate distributions with given marginals, and also to a generalizationof this...

C. m. Cuadras; J. Fortiana

1998-01-01

376

Analysis on the Spatial Distribution of Logistics Industry in South China  

Microsoft Academic Search

We apply methods of exploratory spatial data analysis (ESDA) to examine variation in logistics industry in south China based on the characteristics of regional logistics. This paper investigates the regional disparities at city level in south China by global and local spatial autocorrelation analysis, with the support of Arc Map and Geoda software. It visualizes the regional distribution of logistics

Zhen Zhang

2011-01-01

377

Analysis on the spatial distribution of logistics industry in northeast China  

Microsoft Academic Search

We apply methods of exploratory spatial data analysis (ESDA) to examine variation in logistics industry in northeast China based on the characteristics of regional logistics. This paper investigates the regional disparities at city level in northeast China by global and local spatial autocorrelation analysis, with the support of Geoda software. It visualizes the regional distribution of logistics industry by box

Zhen Zhang

2010-01-01

378

Transformer and load modeling in short circuit analysis for distribution systems  

Microsoft Academic Search

Accuracy of short circuit analysis depends on the modeling of transformers and loads. This paper addresses implementation of various transformer and load models in a short-circuit analysis for three-phase unbalanced distribution systems. Detailed transformer models are derived and incorporated into a production grade short circuit program with three different load models. Our studies show that different transformer connections, load models,

A. Tan; W.-H. E. Liu; D. Shirmohammadi

1997-01-01

379

Incidence, histopathologic analysis and distribution of tumours of the hand  

PubMed Central

Background The aim of this large collective and meticulous study of primary bone tumours and tumourous lesions of the hand was to enhance the knowledge about findings of traumatological radiographs and improve differential diagnosis. Methods This retrospective study reviewed data collected from 1976 until 2006 in our Bone Tumour Registry. The following data was documented: age, sex, radiological investigations, tumour location, histopathological features including type and dignity of the tumour, and diagnosis. Results The retrospective analysis yielded 631 patients with a mean age of 35.9?±?19.2 years. The majority of primary hand tumours were found in the phalanges (69.7%) followed by 24.7% in metacarpals and 5.6% in the carpals. Only 10.6% of all cases were malignant. The major lesion type was cartilage derived at 69.1%, followed by bone cysts 11.3% and osteogenic tumours 8.7%. The dominant tissue type found in phalanges and metacarpals was of cartilage origin. Osteogenic tumours were predominant in carpal bones. Enchondroma was the most commonly detected tumour in the hand (47.1%). Conclusions All primary skeletal tumours can be found in the hand and are most often of cartilage origin followed by bone cysts and osteogenic tumours. This study furthermore raises awareness about uncommon or rare tumours and helps clinicians to establish proper differential diagnosis, as the majority of detected tumours of the hand are asymptomatic and accidental findings on radiographs.

2014-01-01

380

Distributional Benefit Analysis of a National Air Quality Rule  

PubMed Central

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

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

2011-01-01

381

Distributional benefit analysis of a national air quality rule.  

PubMed

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

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

2011-06-01

382

A network analysis of food flows within the United States of America.  

PubMed

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

Lin, Xiaowen; Dang, Qian; Konar, Megan

2014-05-20

383

Hyperdimensional Analysis of Amino Acid Pair Distributions in Proteins  

PubMed Central

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

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

2011-01-01

384

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

385

Strength distribution of reinforcing fibers in a Nicalon fiber/chemically vapor infiltrated silicon carbide matrix composite  

NASA Technical Reports Server (NTRS)

The strength distribution of fibers within a two-dimensional laminate ceramic/ceramic composite consisting of an eight harness satin weave of Nicalon continuous fiber within a chemically vapor infiltrated SiC matrix was determined from analysis of the fracture mirrors of the fibers. Comparison of the fiber strengths and the Weibull moduli with those for Nicalon fibers prior to incorporation into composites suggests that possible fiber damage may occur either during the weaving or during another stage of the composite manufacture. Observations also indicate that it is the higher-strength fibers which experience the greatest extent of fiber pullout and thus make a larger contribution to the overall composite toughness than do the weaker fibers.

Eckel, Andrew J.; Bradt, Richard C.

1989-01-01

386

FASEP ultra-automated analysis of fibre length distribution in glass-fibre-reinforced products  

NASA Astrophysics Data System (ADS)

Reinforced plastic materials are widely used in high sophisticated applications. The length distribution of the fibres influences the mechanical properties of the final product. A method for automatic determination of this length distribution was developed. After separating the fibres out of the composite material without any damage, and preparing them for microscopical analysis, a mosaic of microscope pictures is taken. After image processing and analysis with mathematical methods, a complete statistic of the fibre length distribution could be determined. A correlation between fibre length distribution and mechanical properties, measured e.g. with material test methods, like tensile and impact tests, was found. This is a method to optimize the process and selection of material for the plastic parts. In result this enhances customer satisfaction and, maybe much more important, reduces costs for the manufacturer.

Hartwich, Mark R.; Höhn, Norbert; Mayr, Helga; Sandau, Konrad; Stengler, Ralph

2009-06-01

387

A Lightning Surge Analysis for the Rationalization of the Grounding System in Power Distribution Lines  

NASA Astrophysics Data System (ADS)

The grounding system is one of the most important lightning-protection features of power distribution lines. Based on the statistical distribution of surge currents through lightning arrestors caused by indirect lightning strokes and electrical surges in customers, a rated value of the grounding resistance for lightning arrestors on distribution lines was specified in the 1960's. TEPCO had conducted field research to measure the waveforms of surge voltage and current in order to rationalize the lightning protection design of distribution lines. And the authors proposed a lightning-surges analysis model based on the observation data. In this study, a lightning surge analysis for the rationalization of the grounding system was carried out by means of the EMTP. The calculation conditions were set based on the observation data. The calculated results suggest that a simple grounding design is possible. That can be useful for the Electric Power Companies to manage grounding systems.

Miyazaki, Teru; Okabe, Shigemitsu; Aiba, Kiyoshi; Hirai, Takao; Yoshinaga, Jun

388

Dehydration and phase transformation in chrysotile asbestos—A radial distribution analysis study  

Microsoft Academic Search

Radial distribution analysis of x-ray intensities diffracted by chrysotile samples untreated and treated at different temperatures\\u000a upto 900°C has been carried out. Interatomic distances, coordination numbers, mean square displacements and the interatomic\\u000a coupling constants for different pairs of atoms have been calculated from the radial distribution curves. The interatomic\\u000a distances and octahedral co-ordination number is found to decrease marginally upto

A K Datta; B K Mathur; B K Samantaray; S Bhattacherjee

1987-01-01

389

Analysis of the economic benefits to new energy-saving distribution transformer  

Microsoft Academic Search

Calculating the power loss of amorphous core transformer (AMT), S11 and S7 type distribution transformers in the same capability, and comparative analysis the economic benefits between AMT and S11 type transformer. It can be concluded that the effect of energy-saving of AMT is superior to the energy-saving effect of S11 type distribution transformers, and if replace the S7 type transformer

Zhang Zhi-Gang; Liu Lian-Xiao; Li Zhi-Yong; Pan Jin

2008-01-01

390

Determination of current and temperature distribution in overhead conductors by using electromagnetic-field analysis tools  

Microsoft Academic Search

This paper discusses the issue of skin-effect impact on a current's distribution. It presents an analytical approach for determining temperature distribution by using the Electromagnetic Field Analysis Tool's two-dimensional (2-D) program (ELEFANT 2D) over the cross sections of tube-type conductors. Using this implemented model, the authors determine the conductor's current density by taking into account the skin-effect impact on a

M. Zunec; I. Ticar; F. Jakl

2006-01-01

391

Lateral force distributions for the linear static analysis of base-isolated buildings  

Microsoft Academic Search

This paper presents a new approach for the evaluation of accurate lateral force distributions for the Linear Static Analysis\\u000a (LSA) of Base Isolated (BI-) buildings. In essence, the proposed lateral force distributions depend on a factor measuring\\u000a the degree of non- linearity of the Isolation System (IS) and on the ratio between the effective period of the BI-structure\\u000a (Tis) and

Donatello Cardone; Mauro Dolce; Giuseppe Gesualdi

2009-01-01

392

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

Microsoft Academic Search

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

Daniel Wüstner; Nils J. Færgeman

2008-01-01

393

Apportionment of multiple aerosol size distributions modes using factor analysis techniques  

SciTech Connect

This research in progress is concerned with developing the capability to ojectively partition aerosol size distribution data into a small number of modes, that together explain most of the variation of the observed data. It is desired to determine from analysis in the field of the optical spectrometer data when a particular mode is present and to collect filter samples to determine the chemical composition of that mode. The results would relate aerosol size distributions to chemical composition.

Williams, A.

1990-01-01

394

Apportionment of multiple aerosol size distributions modes using factor analysis techniques  

SciTech Connect

This research in progress is concerned with developing the capability to ojectively partition aerosol size distribution data into a small number of modes, that together explain most of the variation of the observed data. It is desired to determine from analysis in the field of the optical spectrometer data when a particular mode is present and to collect filter samples to determine the chemical composition of that mode. The results would relate aerosol size distributions to chemical composition.

Williams, A.

1990-12-31

395

A Novel Method for Load Flow Analysis of Unbalanced Three-Phase Radial Distribution Networks  

Microsoft Academic Search

This paper presents a novel method for load flow analysis in radially operated 3-phase distribution networks without solving the well-known conventional load flow equations. The method can be applied for distribution systems in which the loads are unbalanced. As the size of matrix used is very small compared to those in conventional methods,the amount of memory used is very small,the

Masoud Aliakbar GOLKAR

2007-01-01

396

Analysis of symmetric Y-junction laser arrays with uniform near-field distribution  

Microsoft Academic Search

The analysis of a Y-junction laser array is presented. It is shown that the lowest-order cavity mode of this array has the lowest threshold gain and is thus preferentially excited. This mode has a uniform near-field distribution. Compared with the sinusoidal near-field distribution of the supermodes of the evanescently coupled laser arrays, this uniformity not only can delay the onset

K.-L. Chen; Shyh Wang

1986-01-01

397

Goodness-of-fit analysis for lumber data  

Microsoft Academic Search

Four different probability distributions were studied to evaluate their relative goodness-of-fit in describing the modulus of rupture (MOR) and modulus of elasticity (MOE) of populations of dimension lumber. The distributions under consideration were the normal, lognormal, Weibull and Johnson's SB. The populations of lumber consisted of 96 data sets of various species groups, mechanical properties, sizes, structural grades and growth

P. J. Pellicane; Fort Collins

1985-01-01

398

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

PubMed Central

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

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

2009-01-01

399

Signal detection analysis of response distributions for intensity and speech judgments  

NASA Astrophysics Data System (ADS)

Schouten and van Hessen [J. Acoust. Soc. Am. 104, 2980-2990 (1998)] reported rating response distributions for intensity and speech continua. These empirical distributions were claimed to reflect each subject's internal decision axes, allowing direct evaluation of the distribution assumptions underlying the common Gaussian equal-variance model signal detection theory (SDT). The observed distributions were deemed roughly Gaussian. However, the original analyses implicitly assume that the rating scale is a direct, interval reflection of internal likelihood values. We used the data instead to construct ROC curves, an analysis that assumes an ordinal relationship between the rating responses and the decision axes. Our ROC analyses show that the representations of the intensity stimuli reasonably approximate a Gaussian model. In contrast, the distributions underlying the speech stimuli are clearly not Gaussian, but imply discrete representations. We discuss appropriate decision models for judgments of intensity and speech continua.

Pastore, Richard E.; MacMillan, Neil A.

2002-05-01

400

Modal analysis of a cantilever beam by use of Brillouin based distributed dynamic strain measurements  

NASA Astrophysics Data System (ADS)

In this work we report an experimental modal analysis of a cantilever beam, carried out by use of a Brillouin optical time-domain analysis (BOTDA) setup operated at a fixed pump-probe frequency shift. The employed technique permitted us to carry out distributed strain measurements along the vibrating beam at a maximum acquisition rate of 108 Hz. The mode shapes of the first three bending modes (1.7, 10.8, 21.6 Hz) were measured for the structure under test. The good agreement between the experimental and numerical results based on a finite-element method (FEM) analysis demonstrates that Brillouin based distributed sensors are well suited to perform the modal analysis of a vibrating structure. This type of analysis may be useful for applications in structural health monitoring where changes in mode shapes are used as indicators of the damage to the structure.

Minardo, Aldo; Coscetta, Agnese; Pirozzi, Salvatore; Bernini, Romeo; Zeni, Luigi

2012-12-01

401

Simplified representation of atmospheric aerosol size distributions using absolute principal component analysis  

NASA Astrophysics Data System (ADS)

Principal component analysis provides a fast and robust method to reduce the data dimensionality of an aerosol size distribution data set. Here we describe a methodology for applying principal component analysis to aerosol size distribution measurements. We illustrate the method by applying it to data obtained during five field studies. Most variations in the sub-micrometer aerosol size distribution over periods of weeks can be described using 5 components. Using 6 to 8 components preserves virtually all the information in the original data. A key aspect of our approach is the introduction of a new method to weight the data; this preserves the orthogonality of the components while taking the measurement uncertainties into account. We also describe a new method for identifying the approximate number of aerosol components needed to represent the measurement quantitatively. Applying Varimax rotation to the resultant components decomposes a distribution into independent monomodal distributions. Normalizing the components provides physical meaning to the component scores. The method is relatively simple, computationally fast, and numerically robust. The resulting data simplification provides an efficient method of representing complex data sets and should greatly assist in the analysis of size distribution data.

Chan, T. W.; Mozurkewich, M.

2007-02-01

402

Simplified representation of atmospheric aerosol size distributions using absolute principal component analysis  

NASA Astrophysics Data System (ADS)

Principal component analysis provides a fast and robust method to reduce the data dimensionality of an aerosol size distribution data set. Here we describe a methodology for applying principal component analysis to aerosol size distribution measurements. We illustrate the method by applying it to data obtained during five field studies. Most variations in the sub-micrometer aerosol size distribution over periods of weeks can be described using 5 components. Using 6 to 8 components preserves virtually all the information in the original data. A key aspect of our approach is the introduction of a new method to weight the data; this preserves the orthogonality of the components while taking the measurement uncertainties into account. We also describe a new method for identifying the approximate number of aerosol components needed to represent the measurement quantitatively. Applying Varimax rotation to the resultant components decomposes a distribution into independent monomodal distributions. Normalizing the components provides physical meaning to the component scores. The method is relatively simply, computationally fast, and numerically robust. The resulting data simplification provides an efficient method of representing complex data sets and should greatly assist in the analysis of size distribution data.

Chan, T. W.; Mozurkewich, M.

2006-10-01

403

powerlaw: A Python Package for Analysis of Heavy-Tailed Distributions  

PubMed Central

Power laws are theoretically interesting probability distributions that are also frequently used to describe empirical data. In recent years, effective statistical methods for fitting power laws have been developed, but appropriate use of these techniques requires significant programming and statistical insight. In order to greatly decrease the barriers to using good statistical methods for fitting power law distributions, we developed the powerlaw Python package. This software package provides easy commands for basic fitting and statistical analysis of distributions. Notably, it also seeks to support a variety of user needs by being exhaustive in the options available to the user. The source code is publicly available and easily extensible.

Alstott, Jeff; Bullmore, Ed; Plenz, Dietmar

2014-01-01

404

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

405

Sensitivity Analysis of CLIMEX Parameters in Modeling Potential Distribution of Phoenix dactylifera L.  

PubMed Central

Using CLIMEX and the Taguchi Method, a process-based niche model was developed to estimate potential distributions of Phoenix dactylifera L. (date palm), an economically important crop in many counties. Development of the model was based on both its native and invasive distribution and validation was carried out in terms of its extensive distribution in Iran. To identify model parameters having greatest influence on distribution of date palm, a sensitivity analysis was carried out. Changes in suitability were established by mapping of regions where the estimated distribution changed with parameter alterations. This facilitated the assessment of certain areas in Iran where parameter modifications impacted the most, particularly in relation to suitable and highly suitable locations. Parameter sensitivities were also evaluated by the calculation of area changes within the suitable and highly suitable categories. The low temperature limit (DV2), high temperature limit (DV3), upper optimal temperature (SM2) and high soil moisture limit (SM3) had the greatest impact on sensitivity, while other parameters showed relatively less sensitivity or were insensitive to change. For an accurate fit in species distribution models, highly sensitive parameters require more extensive research and data collection methods. Results of this study demonstrate a more cost effective method for developing date palm distribution models, an integral element in species management, and may prove useful for streamlining requirements for data collection in potential distribution modeling for other species as well.

Shabani, Farzin; Kumar, Lalit

2014-01-01

406

Sensitivity analysis of CLIMEX parameters in modelling potential distribution of Lantana camara L.  

PubMed

A process-based niche model of L. camara L. (lantana), a highly invasive shrub species, was developed to estimate its potential distribution using CLIMEX. Model development was carried out using its native and invasive distribution and validation was carried out with the extensive Australian distribution. A good fit was observed, with 86.7% of herbarium specimens collected in Australia occurring within the suitable and highly suitable categories. A sensitivity analysis was conducted to identify the model parameters that had the most influence on lantana distribution. The changes in suitability were assessed by mapping the regions where the distribution changed with each parameter alteration. This allowed an assessment of where, within Australia, the modification of each parameter was having the most impact, particularly in terms of the suitable and highly suitable locations. The sensitivity of various parameters was also evaluated by calculating the changes in area within the suitable and highly suitable categories. The limiting low temperature (DV0), limiting high temperature (DV3) and limiting low soil moisture (SM0) showed highest sensitivity to change. The other model parameters were relatively insensitive to change. Highly sensitive parameters require extensive research and data collection to be fitted accurately in species distribution models. The results from this study can inform more cost effective development of species distribution models for lantana. Such models form an integral part of the management of invasive species and the results can be used to streamline data collection requirements for potential distribution modelling. PMID:22815881

Taylor, Subhashni; Kumar, Lalit

2012-01-01

407

Sensitivity Analysis of CLIMEX Parameters in Modelling Potential Distribution of Lantana camara L.  

PubMed Central

A process-based niche model of L. camara L. (lantana), a highly invasive shrub species, was developed to estimate its potential distribution using CLIMEX. Model development was carried out using its native and invasive distribution and validation was carried out with the extensive Australian distribution. A good fit was observed, with 86.7% of herbarium specimens collected in Australia occurring within the suitable and highly suitable categories. A sensitivity analysis was conducted to identify the model parameters that had the most influence on lantana distribution. The changes in suitability were assessed by mapping the regions where the distribution changed with each parameter alteration. This allowed an assessment of where, within Australia, the modification of each parameter was having the most impact, particularly in terms of the suitable and highly suitable locations. The sensitivity of various parameters was also evaluated by calculating the changes in area within the suitable and highly suitable categories. The limiting low temperature (DV0), limiting high temperature (DV3) and limiting low soil moisture (SM0) showed highest sensitivity to change. The other model parameters were relatively insensitive to change. Highly sensitive parameters require extensive research and data collection to be fitted accurately in species distribution models. The results from this study can inform more cost effective development of species distribution models for lantana. Such models form an integral part of the management of invasive species and the results can be used to streamline data collection requirements for potential distribution modelling.

Taylor, Subhashni; Kumar, Lalit

2012-01-01

408

Sensitivity analysis of CLIMEX parameters in modeling potential distribution of Phoenix dactylifera L.  

PubMed

Using CLIMEX and the Taguchi Method, a process-based niche model was developed to estimate potential distributions of Phoenix dactylifera L. (date palm), an economically important crop in many counties. Development of the model was based on both its native and invasive distribution and validation was carried out in terms of its extensive distribution in Iran. To identify model parameters having greatest influence on distribution of date palm, a sensitivity analysis was carried out. Changes in suitability were established by mapping of regions where the estimated distribution changed with parameter alterations. This facilitated the assessment of certain areas in Iran where parameter modifications impacted the most, particularly in relation to suitable and highly suitable locations. Parameter sensitivities were also evaluated by the calculation of area changes within the suitable and highly suitable categories. The low temperature limit (DV2), high temperature limit (DV3), upper optimal temperature (SM2) and high soil moisture limit (SM3) had the greatest impact on sensitivity, while other parameters showed relatively less sensitivity or were insensitive to change. For an accurate fit in species distribution models, highly sensitive parameters require more extensive research and data collection methods. Results of this study demonstrate a more cost effective method for developing date palm distribution models, an integral element in species management, and may prove useful for streamlining requirements for data collection in potential distribution modeling for other species as well. PMID:24722140

Shabani, Farzin; Kumar, Lalit

2014-01-01

409

Statistical analysis of steam generator tube degradation  

Microsoft Academic Search

Statistical methods are investigated for use in evaluating and predicting the progression of steam generator tube degradation due to corrosion and other causes. It is found that the Weibull statistical distribution provides an easy to use and effective method for predicting damage progression. Other statistical functions, such as the log-normal, can also be used, often with essentially equivalent results. Statistical

R. W. Staehle; J. A. Gorman; K. D. Stavropoulos

1991-01-01

410

Weibull Multiplicative Model and Machine Learning Models for Full-Automatic Dark-Spot Detection from SAR Images  

NASA Astrophysics Data System (ADS)

As a major aspect of marine pollution, oil release into the sea has serious biological and environmental impacts. Among remote sensing systems (which is a tool that offers a non-destructive investigation method), synthetic aperture radar (SAR) can provide valuable synoptic information about the position and size of the oil spill due to its wide area coverage and day/night, and all-weather capabilities. In this paper we present a new automated method for oil-spill monitoring. A new approach is based on the combination of Weibull Multiplicative Model and machine learning techniques to differentiate between dark spots and the background. First, the filter created based on Weibull Multiplicative Model is applied to each sub-image. Second, the sub-image is segmented by two different neural networks techniques (Pulsed Coupled Neural Networks and Multilayer Perceptron Neural Networks). As the last step, a very simple filtering process is used to eliminate the false targets. The proposed approaches were tested on 20 ENVISAT and ERS2 images which contained dark spots. The same parameters were used in all tests. For the overall dataset, the average accuracies of 94.05 % and 95.20 % were obtained for PCNN and MLP methods, respectively. The average computational time for dark-spot detection with a 256 × 256 image in about 4 s for PCNN segmentation using IDL software which is the fastest one in this field at present. Our experimental results demonstrate that the proposed approach is very fast, robust and effective. The proposed approach can be applied to the future spaceborne SAR images.

Taravat, A.; Del Frate, F.

2013-09-01

411

Distributed Denial of Service Defense Attack Tradeoff Analysis (DDOS-DATA)  

Microsoft Academic Search

Under sponsorship of the Defense Advanced Research Projects Agency's (DARPA) Fault Tolerant Networks (FTN) program, the Johns Hopkins University Applied Physics Laboratory (JHU\\/APL) has been conducting the distributed denial of service defense attack tradeoff analysis (DDOS-DATA). DDOS-DATA uses analysis to understand DDOS attacks, mitigation technologies, and their interaction. Through this effort, we have developed a better understanding of attacker-to-mitigation and

W. J. Blackert; D. M. Gregg; A. K. Castner; R. L. Hom; R. M. Jokerst; E. M. Kyle

2003-01-01

412

Correlation-aware statistical timing analysis with non-gaussian delay distributions  

Microsoft Academic Search

Process variations have a growing impact on circuit performance for today's integrated circuit (IC) technologies. The Non-Gaussian delay distributions as well as the correlations among delays make statistical timing analysis more challenging than ever. In this paper, we present an efficient block-based statistical timing analysis approach with linear complexity with respect to the circuit size, which can accurately predict Non-Gaussian

Yaping Zhan; Andrzej J. Strojwas; Xin Li; Lawrence T. Pileggi; David Newmark; Mahesh Sharma

2005-01-01

413

Strategic Sequencing for State Distributed PV Policies: A Quantitative Analysis of Policy Impacts and Interactions  

SciTech Connect

State and local policymakers show increasing interest in spurring the development of customer-sited distributed generation (DG), in particular solar photovoltaic (PV) markets. Prompted by that interest, this analysis examines the use of state policy as a tool to support the development of a robust private investment market. This analysis builds on previous studies that focus on government subsidies to reduce installation costs of individual projects and provides an evaluation of the impacts of policies on stimulating private market development.

Doris, E.; Krasko, V.A.

2012-10-01

414

Outlier aware data aggregation in distributed wireless sensor network using robust principal component analysis  

Microsoft Academic Search

To address the problem of outlier detection in wireless sensor networks, in this paper we propose a robust principal component analysis based technique to detect anomalous or faulty sensor data in a distributed wireless sensor network with a focus on data integrity and accuracy problem. The main key features are that it considers the correlation existing among the sensor data

N. Chitradevi; V. Palanisamy; K. Baskaran; U. B. Nisha

2010-01-01

415

Size-Distribution Analysis of Macromolecules by Sedimentation Velocity Ultracentrifugation and Lamm Equation Modeling  

Microsoft Academic Search

A new method for the size-distribution analysis of polymers by sedimentation velocity analytical ultracentrifugation is described. It exploits the ability of Lamm equation modeling to discriminate between the spreading of the sedimentation boundary arising from sample heterogeneity and from diffusion. Finite element solutions of the Lamm equation for a large number of discrete noninteracting species are combined with maximum entropy

Peter Schuck

2000-01-01

416

Geomorphic features of a badland (biancane) area (Central Italy): characterisation, distribution and quantitative spatial analysis  

Microsoft Academic Search

The biancana landscapes, rather common in several Italian areas, have a very complex morphology. Different geomorphic features often occur along the same hillslope. From a morphological survey of an experimental site in southern Tuscany, the forms were classified, and their distribution analysed. Spatial analysis of the biancane provided insights into the range of forces responsible for their formation and evolution.

Costanza Calzolari; Fabrizio Ungaro

1998-01-01

417

Analysis of a cone-based distributed topology control algorithm for wireless multi-hop networks  

Microsoft Academic Search

The topology of a wireless multi-hop network can be controlled by varying the transmission power at each node. In this paper, we give a detailed analysis of a cone-based distributed topology control algorithm. This algorithm, introduced in [16], does not assume that nodes have GPS information available; rather it depends only on directional information. Roughly speaking, the basic idea of

Li Li; Joseph Y. Halpern; Paramvir Bahl; Yi-Min Wang; Roger Wattenhofer

2001-01-01

418

Distributed, Collaborative Data Analysis from Heterogeneous Sites Using a Scalable Evolutionary Technique  

Microsoft Academic Search

This paper documents an early effort to develop an experimental, collaborative data analysis technique for learning classifiers from a collection of heterogeneous datasets distributed over a network. The proposed technique makes use of a scalable evolutionary algorithm, called the GEMGA to classify datasets. This paper describes the developed technique and the results of the use of this technique through the

H. Kargupta; E. Johnson; E. Sanseverino; D. Hershberger; L. Silvestre

2002-01-01

419

Analysis and minimization of losses in electric-power transmission and distribution systems  

Microsoft Academic Search

A comprehensive approach is taken to the loss analysis and minimization in electrical power systems at both transmission and distribution levels. New methods were developed to calculate the power and energy losses in bulk-power transmission systems. The methods incorporate the effect of the actual on-line control and operation of the system to improve the accuracy of calculations. To calculate the

Baran

1988-01-01

420

Mapping a forest mosaic – A comparison of vegetation and bird distributions using geographic boundary analysis  

Microsoft Academic Search

Many areas of ecological inquiry require the ability to detect and characterize change in ecological variables across both space and time. The purpose of this study was to investigate ways in which geographic boundary analysis techniques could be used to characterize the pattern of change over space in plant distributions in a forested wetland mosaic. With vegetation maps created using

Kimberly R. Hall; Susan L. Maruca

2001-01-01

421

Analysis of electromagnetic force distribution on end winding for motor reliance  

Microsoft Academic Search

The design of electrical rotating machine is required to have high capacity and electrical loading without comparable increase in size. In this paper, we looked into the electromagnetic force of end winding part of electrical motor by using 3D finite element method to analyze distribution of end winding forces more exactly. And we also performed stress analysis of end windings

Ki-Chan Kim; Kab-Jae Lee; Ju Lee

2005-01-01

422

Systematic analysis of transverse momentum distribution and non-extensive thermodynamics theory  

SciTech Connect

A systematic analysis of transverse momentum distribution of hadrons produced in ultrarelativistic p+p and A+A collisions is presented. We investigate the effective temperature and the entropic parameter from the non-extensive thermodynamic theory of strong interaction. We conclude that the existence of a limiting effective temperature and of a limiting entropic parameter is in accordance with experimental data.

Sena, I.; Deppman, A. [Instituto de Fisica - Universidade de Sao Paulo (Brazil)

2013-03-25

423

Estimating Flexible Distributions of Ideal-Points with External Analysis of Preferences.  

ERIC Educational Resources Information Center

Two ideal-point probabilistic choice models from the external analysis of preferences are presented that allow for more flexible distributions of ideal-points. The first extends the probit model of W. Kamakura and R. Srivastava. The second is based on simplifying assumptions that lead to a multidimensional histogram of ideal-points. (SLD)

Kamakura, Wagner A.

1991-01-01

424

An Ecological Analysis of the Geographic Distribution of Veterinarians in the United States  

ERIC Educational Resources Information Center

Measures of the ecological characteristics of states were developed through factor analysis. Then ecological characteristics of states and cities were related to the geographic distribution of veterinarians and physicians. Population size is the strongest correlate of the number of health professionals. Results for pet veterinarians resemble…

Richards, James M., Jr.

1977-01-01

425

Comparison of deuterium incorporation and mass isotopomer distribution analysis for measurement of human cholesterol biosynthesis  

Microsoft Academic Search

To compare endogenous cholesterol biosynthesis measured by deuterium incorporation (DI) and mass isoto- pomer distribution analysis (MIDA), cholesterol fractional and absolute synthetic rates were measured simultaneously by both techniques under identical physiological condi- tions. Twelve subjects (22 to 39 years of age) underwent a dual stable isotope protocol, involving oral deuterium oxide administration and measurement of incorporation of deute- rium

Marco Di Buono; Peter J. H. Jones; Louis Beaumier; Linda J. Wykes

426

Distributed intelligent architecture for falling detection and physical activity analysis in the elderly  

Microsoft Academic Search

A novel approach for the detection of falls, the analysis of body postures, mobility and metabolic energy expenditure of elderly people has been developed. It is based on a distributed intelligence architecture, supported by it wireless personal area network (WPAN) which allows a full 24-hour supervision of the user, both indoor and outdoor home. An open design methodology lets the

M. Prado; J. Reina-Tosina; L. Roa

2002-01-01

427

Studies on supply logistics distribution center location based on principal component analysis for coal enterprise  

Microsoft Academic Search

The location of logistics distribution center holds an very important position in the coal enterprise supply logistics system planning, the decision-makers need to consider various factors comprehensively. The traditional location method considers little about the interaction between the indexes during the location process. This paper introduce the principal component analysis (PCA)method in the location of logistics, and use this method

Wensheng Wang; Qingyang Zhao

2010-01-01

428

Spatiotemporal Load-Analysis Model for Electric Power Distribution Facilities Using Consumer Meter-Reading Data  

Microsoft Academic Search

The load analysis for the distribution system and facilities has relied on measurement equipment. Moreover, load monitoring incurs huge costs in terms of installation and main- tenance. This paper presents a new model to analyze wherein facilities load under a feeder every 15 min using meter-reading data that can be obtained from a power consumer every 15 min or a

Jin-Ho Shin; Bong-Jae Yi; Young-Il Kim; Heon-Gyu Lee; Keun Ho Ryu

2011-01-01

429

A simplified approach for load flow analysis of radial distribution network with embedded generation  

Microsoft Academic Search

This paper presents a simple approach for load flow analysis of a radial distribution network with embedded generation. The proposed approach utilizes forward and backward sweep algorithm based on Kirchoffpsilas current law (KCL) and Kirchoffpsilas voltage law (KVL) for evaluating the node voltages iteratively. In this approach, computation of branch current depends only on the current injected at the neighbouring

K Vinoth Kumar; M. P. Selvan

2008-01-01

430

A Simplified Approach for Load Flow Analysis of Radial Distribution Network  

Microsoft Academic Search

This paper presents a simple approach for load flow analysis of a radial distribution network. The proposed approach utilizes forward and backward sweep algorithm based on Kirchoff's current law (KCL) and Kirchoff's voltage law (KVL) for evaluating the node voltages iteratively. In this approach, computation of branch current depends only on the current injected at the neighbouring node and the

K. Vinoth Kumar; M. P. Selvan

2008-01-01

431

Continuous dose-response modeling and risk analysis with the gamma and reciprocal gamma distributions  

Microsoft Academic Search

Kodell and West (1993) describe two methods for calculating pointwise upper confidence limits on the risk function with normally distributed responses and using a certain definition of adverse quantitative effect. But Banga et al. (2000) have shown that these normal theory methods break down when applied to skew data. We accordingly develop a risk analysis model and associated likelihood-based methodology

Senin Banga; Ganapati P. Patil; Charles Taillie

2002-01-01

432

Global Sensitivity Analysis of a Distributed Hydrologic Model Using Latin Hypercube Sampling  

Microsoft Academic Search

Having a good understanding of sensitive model parameters is vital for effective calibration of highly parameterized distributed hydrologic models. A Latin Hypercube Sampling and Multiple-Linear Regression based global sensitivity analysis approach is used in this study to investigate the effect of model parameter variability on simulated stages in the Everglades National Park (ENP) in Florida, USA. The study is conducted

T. Dessalegne; S. U. Senarath; R. J. Novoa

2009-01-01

433

An Analysis of Variance Approach for the Estimation of Response Time Distributions in Tests  

ERIC Educational Resources Information Center

Generalizability theory and analysis of variance methods are employed, together with the concept of objective time pressure, to estimate response time distributions and the degree of time pressure in timed tests. By estimating response time variance components due to person, item, and their interaction, and fixed effects due to item types and…

Attali, Yigal

2010-01-01

434

Global Distribution of Tropospheric Aerosols: A 3-D Model Analysis of Satellite Data  

NASA Technical Reports Server (NTRS)

This report describes objectives completed for the GACP (Global Climatology Aerosol Project). The objectives included the analysis of satellite aerosol data, including the optical properties and global distributions of major aerosol types, and human contributions to major aerosol types. The researchers have conducted simulations and field work.

Chin, Mian

2002-01-01

435

Elemental regional distribution in human brain tumours — PIXE analysis of biopsy and autopsy samples  

NASA Astrophysics Data System (ADS)

The elemental regional distribution in human brain tissue was obtained using PIXE analysis. A histo-pathological investigation was used to classify the samples into three different groups: (1) normal tissue, (2) tumour front and (3) tumour centre. Significant differences between the mean values of phosphorous, calcium, iron, zinc and selenium concentrations in each group are reported.

Tapper, U. A. S.; Malmqvist, K. G.; Brun, A.; Salford, L. G.

1987-03-01

436

Infrared thermoimage analysis as real time technique to evaluate in-field pesticide spraying quality distribution  

NASA Astrophysics Data System (ADS)

Tests and calibration of sprayers have been considered a very important task for chemicals use reduction in agriculture and for improvement of plant phytosanitary protection. A reliable, affordable and easy-to-use method to observe the distribution in the field is required and the infrared thermoimage analysis can be considered as a potential method based on non-contact imaging technologies. The basic idea is that the application of colder water (10 °C less) than the leaves surface makes it possible to distinguish and measure the targeted areas by means of a infrared thermoimage analysis based on significant and time persistent thermal differences. Trials were carried out on a hedge of Prunus laurocerasus, 2.1 m height with an homogenous canopy. A trailed orchard sprayer was employed with different spraying configurations. A FLIRTM (S40) thermocamera was used to acquire (@ 50 Hz) thermal videos, in a fixed position, at frame rate of 10 images/s, for nearly 3 min. Distribution quality was compared to the temperature differences obtained from the thermal images between pre-treatment and post-treatment (?T)., according two analysis: time-trend of ?T average values for different hedge heights and imaging ?T distribution and area coverage by segmentation in k means clustering after 30 s of spraying. The chosen spraying configuration presented a quite good distribution for the entire hedge height with the exclusion of the lower (0-1 m from the ground) and the upper part (>1.9 m). Through the image segmentation performed of ?T image by k-means clustering, it was possible to have a more detailed and visual appreciation of the distribution quality among the entire hedge. The thermoimage analysis revealed interesting potentiality to evaluate quality distribution from orchards sprayers.

Menesatti, P.; Biocca, M.

2007-09-01

437

Generalized recurrence plots for the analysis of images from spatially distributed systems  

NASA Astrophysics Data System (ADS)

We propose a new method for the analysis of images showing patterns emerging from the evolution of spatially distributed systems. The generalized recurrence plot (GRP) and the generalized recurrence quantification analysis (GRQA) are exploited for the investigation of such patterns. We focus on snapshots of spatio-temporal processes such as the formation of Turing structures and traveling waves in the Belousov-Zhabotinsky reaction, satellite images of spatial chlorophyll distribution in seas and oceans (similar to turbulent flows), colonies of Dyctiostelium discoideum, fractals, and noise. The method is based on the GRP and GRQA and particularly on the measures determinism (DET) and entropy (ENT), providing a new criterion for the assessment and classification of images based on the simultaneous evaluation of their global and local structure. The DET-ENT diagram is introduced and compared with the classical image analysis entropy defined on the pixels’ values. The method proposed provides appealing performances in the case of images showing complex spatial patterns.

Facchini, Angelo; Mocenni, Chiara; Vicino, Antonio

2009-01-01

438

Water distribution system vulnerability analysis using weighted and directed network models  

NASA Astrophysics Data System (ADS)

The reliability and robustness against failures of networked water distribution systems are central tenets of water supply system design and operation. The ability of such networks to continue to supply water when components are damaged or fail is dependent on the connectivity of the network and the role and location of the individual components. This paper employs a set of advanced network analysis techniques to study the connectivity of water distribution systems, its relationship with system robustness, and susceptibility to damage. Water distribution systems are modeled as weighted and directed networks by using the physical and hydraulic attributes of system components. A selection of descriptive measurements is utilized to quantify the structural properties of benchmark systems at both local (component) and global (network) scales. Moreover, a novel measure of component criticality, the demand-adjusted entropic degree, is proposed to support identification of critical nodes and their ranking according to failure impacts. The application and value of this metric is demonstrated through two case study networks in the USA and UK. Discussion focuses on the potential for gradual evolution of abstract graph-based tools and techniques to more practical network analysis methods, where a theoretical framework for the analysis of robustness and vulnerability of water distribution networks to better support planning and management decisions is presented.

Yazdani, Alireza; Jeffrey, Paul

2012-06-01

439

Rank-Ordered Multifractal Analysis (ROMA) of probability distributions in fluid turbulence  

NASA Astrophysics Data System (ADS)

Rank-Ordered Multifractal Analysis (ROMA) was introduced by Chang and Wu (2008) to describe the multifractal characteristic of intermittent events. The procedure provides a natural connection between the rank-ordered spectrum and the idea of one-parameter scaling for monofractals. This technique has successfully been applied to MHD turbulence simulations and turbulence data observed in various space plasmas. In this paper, the technique is applied to the probability distributions in the inertial range of the turbulent fluid flow, as given in the vast Johns Hopkins University (JHU) turbulence database. In addition, a new way of finding the continuous ROMA spectrum and the scaled probability distribution function (PDF) simultaneously is introduced.

Wu, C. C.; Chang, T.

2011-04-01

440

Circulatory model of vascular and interstitial distribution kinetics of rocuronium: a population analysis in patients.  

PubMed

The time-course of the neuromuscular blocking effect of rocuronium depends on circulatory mixing and the rate of distribution into the interstitial space. In order to quantitatively evaluate these processes, a physiologically meaningful model of distribution kinetics based on circulatory transport and interstitial diffusion, was fitted to rocuronium disposition data in 10 patients using a population approach. Information on cardiac output and circulatory mixing was obtained from the kinetics of indocyanine green (ICG), which was injected simultaneously with rocuronium. As a compromise between physiological reality and parameter identifiability, the organs of the systemic circulation were lumped into a heterogeneous subsystem, described by an axially distributed model of extravascular diffusion. Diffusion into the interstitial space determines the rate of rocuronium distribution in the body (diffusional time constant 89 min). The resulting whole body distribution kinetics depends both on cardiac output and on the apparent permeability surface area product (0.16 l/min). The analysis of the ICG data revealed that heterogeneity of blood transit time through the systemic circulation decreased and that cardiopulmonary volume increased, respectively, with cardiac output. The approach should be useful for studying the effect of disease states on distribution kinetics of drugs. PMID:21125318

Weiss, Michael; Reekers, Marije; Vuyk, Jaap; Boer, Fred

2011-04-01

441

Finite difference based vibration simulation analysis of a segmented distributed piezoelectric structronic plate system  

NASA Astrophysics Data System (ADS)

Electrical modeling of piezoelectric structronic systems by analog circuits has the disadvantages of huge circuit structure and low precision. However, studies of electrical simulation of segmented distributed piezoelectric structronic plate systems (PSPSs) by using output voltage signals of high-speed digital circuits to evaluate the real-time dynamic displacements are scarce in the literature. Therefore, an equivalent dynamic model based on the finite difference method (FDM) is presented to simulate the actual physical model of the segmented distributed PSPS with simply supported boundary conditions. By means of the FDM, the four-ordered dynamic partial differential equations (PDEs) of the main structure/segmented distributed sensor signals/control moments of the segmented distributed actuator of the PSPS are transformed to finite difference equations. A dynamics matrix model based on the Newmark-? integration method is established. The output voltage signal characteristics of the lower modes (m <= 3, n <= 3) with different finite difference mesh dimensions and different integration time steps are analyzed by digital signal processing (DSP) circuit simulation software. The control effects of segmented distributed actuators with different effective areas are consistent with the results of the analytical model in relevant references. Therefore, the method of digital simulation for vibration analysis of segmented distributed PSPSs presented in this paper can provide a reference for further research into the electrical simulation of PSPSs.

Ren, B. Y.; Wang, L.; Tzou, H. S.; Yue, H. H.

2010-08-01

442

Spatial point pattern analysis of aerial survey data to assess clustering in wildlife distributions  

NASA Astrophysics Data System (ADS)

Assessing clustering in wildlife populations is crucial for understanding their dynamics. This assessment is made difficult for data obtained through aerial surveys because the shape and size of sampling units (strip transects) result in poor data supports, which generally hampers spatial analysis of these data. The problem may be solved by having more detailed data where exact locations of observed animal groups are recorded. These data, obtainable through GPS technology, are amenable to spatial analysis, thereby allowing spatial point pattern analysis to be used to assess observed spatial patterns relative to environmental factors like vegetation. Distance measures like the G-statistic and K-function classify such patterns into clustered, regular or completely random patterns, while independence between species is assessed through a multivariate extension of the K-function. Quantification of clustering is carried out using spatial regression. The techniques are illustrated with field data on three ungulates observed in an ecosystem in Kenya. Results indicate a relation between species spatial distribution and their dietary requirements, thereby concluding the usefulness of spatial point pattern analysis in investigating species spatial distribution. It also provides a technique for explaining and differentiating the distribution of wildlife species.

Khaemba, Wilson Mwale

443

Fluorescence-Intensity Distribution Analysis and Its Application in Biomolecular Detection Technology  

NASA Astrophysics Data System (ADS)

A methodology, fluorescence-intensity distribution analysis, has been developed for confocal microscopy studies in which the fluorescence intensity of a sample with a heterogeneous brightness profile is monitored. An adjustable formula, modeling the spatial brightness distribution, and the technique of generating functions for calculation of theoretical photon count number distribution serve as the two cornerstones of the methodology. The method permits the simultaneous determination of concentrations and specific brightness values of a number of individual fluorescent species in solution. Accordingly, we present an extremely sensitive tool to monitor the interaction of fluorescently labeled molecules or other microparticles with their respective biological counterparts that should find a wide application in life sciences, medicine, and drug discovery. Its potential is demonstrated by studying the hybridization of 5'-(6-carboxytetramethylrhodamine)-labeled and nonlabeled complementary oligonucleotides and the subsequent cleavage of the DNA hybrids by restriction enzymes.

Kask, Peet; Palo, Kaupo; Ullmann, Dirk; Gall, Karsten

1999-11-01

444

Intrinsic charm parton distribution functions from CTEQ-TEA global analysis  

NASA Astrophysics Data System (ADS)

We study the possibility of intrinsic (nonperturbative) charm in parton distribution functions (PDF) of the proton, within the context of the CT10 next-to-next-to-leading order global analysis. Three models for the intrinsic charm (IC) quark content are compared: (i) c^(x)=0 (zero-IC model); (ii) c^(x) is parametrized by a valence-like parton distribution (BHPS model); (iii) c^(x) is parametrized by a sea-like parton distribution (SEA model). In these models, the intrinsic charm content, c^(x), is included in the charm PDF at the matching scale Qc=mc=1.3 GeV. The best fits to data are constructed and compared. Correlations between the value of mc and the amount of IC are also considered.

Dulat, Sayipjamal; Hou, Tie-Jiun; Gao, Jun; Huston, Joey; Pumplin, Jon; Schmidt, Carl; Stump, Daniel; Yuan, C.-P.

2014-04-01

445

[Analysis of streamer properties and emission spectroscopy of 2-D OH distribution of pulsed corona discharge].  

PubMed

Streamer plays a key role in the process of OH radical generation. The propagation of primary and secondary streamers of positive wire-plate pulsed corona discharge was observed using a short gate ICCD in air environment. The influence of the applied voltage on the properties was investigated. It was shown that the primary streamer propagation velocity, electric coverage and length of secondary streamer increased significantly with increasing the applied voltage. Then 2-D OH distribution was investigated by the emission spectrum. With the analysis of the OH emission spectra, the distribution of OH radicals showed a trend of decreasing from the wire electrode to its circumambience. Compared with the streamer propagation trace, the authors found that OH radical distribution and streamer are in the same area. Both OH radical concentration and the intensity of streamer decreased when far away from the wire electrode. PMID:22242481

Zhao, Lei; Gao, Xiang; Luo, Zhong-Yang; Xuan, Jian-Yong; Jiang, Jian-Ping; Cen, Ke-Fa

2011-11-01

446

Husimi distribution and phase-space analysis of a vibron-model quantum phase transition  

NASA Astrophysics Data System (ADS)

The Husimi distribution is proposed for a phase-space analysis of quantum phase transitions in the two-dimensional U(3) vibron model for N-size molecules. We show that the inverse participation ratio and Wehrl's entropy of the Husimi distribution give sharp signatures of the quantum (shape) phase transition from linear to bent. Numerical results are complemented with a variational approach using parity-symmetry-adapted U(3) coherent states, which reach the minimum Wehrl entropy (N(3+2N))/((N+1)(N+2)), in the rigidly linear phase, according to a generalized Wehrl-Lieb conjecture. We also propose a characterization of the vibron-model quantum phase transition by means of the zeros of the Husimi distribution.

Calixto, M.; del Real, R.; Romera, E.

2012-09-01

447

Principal Effects of Axial Load on Moment-Distribution Analysis of Rigid Structures  

NASA Technical Reports Server (NTRS)

This thesis presents the method of moment distribution modified to include the effect of axial load upon the bending moments. This modification makes it possible to analyze accurately complex structures, such as rigid fuselage trusses, that heretofore had to be analyzed by approximate formulas and empirical rules. The method is simple enough to be practicable even for complex structures, and it gives a means of analysis for continuous beams that is simpler than the extended three-moment equation now in common use. When the effect of axial load is included, it is found that the basic principles of moment distribution remain unchanged, the only difference being that the factors used, instead of being constants for a given member, become functions of the axial load. Formulas have been developed for these factors, and curves plotted so that their applications requires no more work than moment distribution without axial load. Simple problems have been included to illustrate the use of the curves.

James, Benjamin Wylie

1935-01-01

448

Analysis and evaluation of planned and delivered dose distributions: practical concerns with ?- and ?- Evaluations  

NASA Astrophysics Data System (ADS)

One component of clinical treatment validation, for example in the commissioning of new radiotherapy techniques or in patient specific quality assurance, is the evaluation and verification of planned and delivered dose distributions. Gamma and related tests (such as the chi evaluation) have become standard clinical tools for such work. Both functions provide quantitative comparisons between dose distributions, combining dose difference and distance to agreement criteria. However, there are some practical considerations in their utilization that can compromise the integrity of the tests, and these are occasionally overlooked especially when the tests are too readily adopted from commercial software. In this paper we review the evaluation tools and describe some practical concerns. The intent is to provide users with some guidance so that their use of these evaluations will provide valid rapid analysis and visualization of the agreement between planned and delivered dose distributions.

Schreiner, L. J.; Holmes, O.; Salomons, G.

2013-06-01

449

Work distribution in a time-dependent logarithmic-harmonic potential: exact results and asymptotic analysis  

NASA Astrophysics Data System (ADS)

We investigate the distribution of work performed on a Brownian particle in a time-dependent asymmetric potential well. The potential has a harmonic component with a time-dependent force constant and a time-independent logarithmic barrier at the origin. For an arbitrary driving protocol, the problem of solving the Fokker-Planck equation for the joint probability density of work and particle position is reduced to the solution of the Riccati differential equation. For a particular choice of the driving protocol, an exact solution of the Riccati equation is presented. An asymptotic analysis of the resulting expression yields the tail behavior of the work distribution for small and large work values. In the limit of a vanishing logarithmic barrier, the work distribution for the breathing parabola model is obtained.

Ryabov, Artem; Dierl, Marcel; Chvosta, Petr; Einax, Mario; Maass, Philipp

2013-02-01

450

Validation results of the IAG Dancer project for distributed GPS analysis  

NASA Astrophysics Data System (ADS)

The number of permanent GPS stations in the world has grown far too large to allow processing of all this data at analysis centers. The majority of these GPS sites do not even make their observation data available to the analysis centers, for various valid reasons. The current ITRF solution is still based on centralized analysis by the IGS, and subsequent densification of the reference frame via regional network solutions. Minor inconsistencies in analysis methods, software systems and data quality imply that this centralized approach is unlikely to ever reach the ambitious accuracy objectives of GGOS. The dependence on published data also makes it clear that a centralized approach will never provide a true global ITRF solution for all GNSS receivers in the world. If the data does not come to the analysis, the only alternative is to bring the analysis to the data. The IAG Dancer project has implemented a distributed GNSS analysis system on the internet in which each receiver can have its own analysis center in the form of a freely distributed JAVA peer-to-peer application. Global parameters for satellite orbits, clocks and polar motion are solved via a distributed least squares solution among all participating receivers. A Dancer instance can run on any computer that has simultaneous access to the receiver data and to the public internet. In the future, such a process may be embedded in the receiver firmware directly. GPS network operators can join the Dancer ITRF realization without having to publish their observation data or estimation products. GPS users can run a Dancer process without contributing to the global solution, to have direct access to the ITRF in near real-time. The Dancer software has been tested on-line since late 2011. A global network of processes has gradually evolved to allow stabilization and tuning of the software in order to reach a fully operational system. This presentation reports on the current performance of the Dancer system, and demonstrates the obvious benefits of distributed analysis of geodetic data in general. IAG Dancer screenshot

Boomkamp, H.

2012-12-01

451

A performance analysis method for distributed real-time robotic systems: A case study of remote teleoperation  

NASA Technical Reports Server (NTRS)

Robot coordination and control systems for remote teleoperation applications are by necessity implemented on distributed computers. Modeling and performance analysis of these distributed robotic systems is difficult, but important for economic system design. Performance analysis methods originally developed for conventional distributed computer systems are often unsatisfactory for evaluating real-time systems. The paper introduces a formal model of distributed robotic control systems; and a performance analysis method, based on scheduling theory, which can handle concurrent hard-real-time response specifications. Use of the method is illustrated by a case of remote teleoperation which assesses the effect of communication delays and the allocation of robot control functions on control system hardware requirements.

Lefebvre, D. R.; Sanderson, A. C.

1994-01-01

452

Determination limits and distribution function of ultraviolet absorbing substances in liquid chromatographic analysis of plant extracts  

SciTech Connect

A study was made of the accuracy of quantitative high-performance liquid chromatographic (HPLC) determinations of UV absorbing substances in plant extracts. By use of gradient elution on a reversed-phase column and UV detection, 62 extracts from plant leaves were investigated. The obtained chromatograms provided a distribution function of the relative abundance of observed peak areas. A computer simulation of such plant extract analyses permitted the estimation of the real distribution function of component absorbances. By use of the same simulations, the probability that a given determination could be performed with success was obtained. These data should be helpful to analysts working on the chromatographic analysis of such samples to estimate the accuracy of a particular determination in quantitative terms. Realistic determination limits for phenolic compounds in plant extracts were defined and computed. The same method can be applied to the analysis of other biological samples and to other chromatographic techniques. 7 figures, 1 table.

Nagels, L.J.; Creten, W.L.; Vanpeperstraete, P.M.

1983-02-01

453

MINBU Distribution of Two-Dimensional Quantum Gravity:. Simulation Result and Semiclassical Analysis  

NASA Astrophysics Data System (ADS)

We analyze the MINBU distribution of two-dimensional quantum gravity. New data of R2-gravity by the Monte Carlo simulation and its theoretical analysis by the semiclassical approach are presented. In the distribution, the cross-over phenomenon takes place at some size of the baby universe where the randomness competes with the smoothing (or roughening) force of R2-term. The dependence on the central charge cm and on the R2-coupling are explained for R2-gravity, which includes the ordinary 2d quantum gravity. The R2-Liouville solution plays the central role in the semiclassical analysis. A total derivative term (surface term) and the infrared regularization play important roles. The surface topology is that of a sphere.

Ichinose, S.; Tsuda, N.; Yukawa, T.

454

Risk analysis of highly combustible gas storage, supply, and distribution systems in PWR plants  

SciTech Connect

This report presents the evaluation of the potential safety concerns for pressurized water reactors (PWRs) identified in Generic Safety Issue 106, Piping and the Use of Highly Combustible Gases in Vital Areas. A Westinghouse four-loop PWR plant was analyzed for the risk due to the use of combustible gases (predominantly hydrogen) within the plant. The analysis evaluated an actual hydrogen distribution configuration and conducted several sensitivity studies to determine the potential variability among PWRs. The sensitivity studies were based on hydrogen and safety-related equipment configurations observed at other PWRs within the United States. Several options for improving the hydrogen distribution system design were identified and evaluated for their effect on risk and core damage frequency. A cost/benefit analysis was performed to determine whether alternatives considered were justifiable based on the safety improvement and economics of each possible improvement.

Simion, G.P. [Science Applications International Corp., Albuquerque, NM (United States); VanHorn, R.L.; Smith, C.L.; Bickel, J.H.; Sattison, M.B. [EG and G Idaho, Inc., Idaho Falls, ID (United States); Bulmahn, K.D. [SCIENTECH, Inc., Idaho Falls, ID (United States)

1993-06-01

455

Passive-scheme analysis for solving the untrusted source problem in quantum key distribution  

SciTech Connect

As a practical method, the passive scheme is useful to monitor the photon statistics of an untrusted source in a 'Plug and Play' quantum key distribution (QKD) system. In a passive scheme, three kinds of monitor mode can be adopted: average photon number (APN) monitor, photon number analyzer (PNA), and photon number distribution (PND) monitor. In this paper, the security analysis is rigorously given for the APN monitor, while for the PNA, the analysis, including statistical fluctuation and random noise, is addressed with a confidence level. The results show that the PNA can achieve better performance than the APN monitor and can asymptotically approach the theoretical limit of the PND monitor. Also, the passive scheme with the PNA works efficiently when the signal-to-noise ratio (R{sup SN}) is not too low and so is highly applicable to solve the untrusted source problem in the QKD system.

Peng Xiang; Xu Bingjie; Guo Hong [CREAM Group, State Key Laboratory of Advanced Optical Communication Systems and Networks (Peking University) and Institute of Quantum Electronics, School of Electronics Engineering and Computer Science, Peking University, Beijing 100871 (China)

2010-04-15

456

Analysis of spatial distribution of mining tremors occurring in Rudna copper mine (Poland)  

NASA Astrophysics Data System (ADS)

The distribution of mining tremors is strictly related to the exploitation progress of mining works and, consequently, to the local stress field. In case the distribution is known, it is possible to determine future area of intensive seismicity in exploited mining panel. In the paper, an analysis of working face-to-tremor distance for Rudna copper mine in Poland is presented. In order to develop a spatial model of tremors' occurrence in the exploited mine, the seismicity of four mining sections in the five-month period was investigated and the tremors' distribution was obtained. It was compared with the spatial distribution of tremors in coal mines found in the literature. The results show that the places where tremors mostly occur — the vicinity of the face, in front of it — coincide with the high-stress area predicted by literature models. The obtained results help to predict the future seismic zone connected with planned mining section, which can be used in seismic hazard analysis.

Koz?owska, Maria

2013-10-01

457

Sensitivity analysis for large-deflection and postbuckling responses on distributed-memory computers  

NASA Technical Reports Server (NTRS)

A computational strategy is presented for calculating sensitivity coefficients for the nonlinear large-deflection and postbuckling responses of laminated composite structures on distributed-memory parallel computers. The strategy is applicable to any message-passing distributed computational environment. The key elements of the proposed strategy are: (1) a multiple-parameter reduced basis technique; (2) a parallel sparse equation solver based on a nested dissection (or multilevel substructuring) node ordering scheme; and (3) a multilevel parallel procedure for evaluating hierarchical sensitivity coefficients. The hierarchical sensitivity coefficients measure the sensitivity of the composite structure response to variations in three sets of interrelated parameters; namely, laminate, layer and micromechanical (fiber, matrix, and interface/interphase) parameters. The effectiveness of the strategy is assessed by performing hierarchical sensitivity analysis for the large-deflection and postbuckling responses of stiffened composite panels with cutouts on three distributed-memory computers. The panels are subjected to combined mechanical and thermal loads. The numerical studies presented demonstrate the advantages of the reduced basis technique for hierarchical sensitivity analysis on distributed-memory machines.

Watson, Brian C.; Noor, Ahmed K.

1995-01-01

458

Fragment distribution as an aid to forensic failure investigations at the scene of explosions  

Microsoft Academic Search

Twelve pipe bombs were exploded, and the fragments were collected and weighed. The distribution of fragment masses was shown\\u000a to follow a Weibull-type form M (n)=M0 [1 ? exp (?Bn?)] when RDX-based military explosives were used and a bimodal distribution when commercial explosives were used. The constant,\\u000a B, was a function of the mass of fragments recovered, making its use

R. Dean; M. R. Edwards

2002-01-01

459

Modeling diameter distribution of the broadleaved-Korean pine mixed forest on Changbai Mountains of China  

Microsoft Academic Search

The broadleaved-Korean pine mixed forest is a native vegetation in the Changbai Mountains, northeast China. The probability\\u000a density functions including the normal, negative exponential, Weibull and finite mixture distribution, were used to describe\\u000a the diameter distributions of the species groups and entire forest stand. There is a strong correlation between parameters\\u000a and mean DBH except the shape parameters in the

Shunzhong Wang; Limin Dai; Guohua Liu; Jianqiong Yuan; Hengmin Zhang; Qingli Wang

2006-01-01

460

Simulation of flight maneuver-load distributions by utilizing stationary, non-Gaussian random load histories  

NASA Technical Reports Server (NTRS)

Random numbers were generated with the aid of a digital computer and transformed such that the probability density function of a discrete random load history composed of these random numbers had one of the following non-Gaussian distributions: Poisson, binomial, log-normal, Weibull, and exponential. The resulting random load histories were analyzed to determine their peak statistics and were compared with cumulative peak maneuver-load distributions for fighter and transport aircraft in flight.

Leybold, H. A.

1971-01-01

461

Measurement of Wheat Starch Granule Size Distribution Using Image Analysis and Laser Diffraction Technology  

Microsoft Academic Search

Cereal Chem. 83(3):259-268 Starch was isolated from flour of four wheats representing hard red winter (Karl), hard red spring (Gunner), durum (Belfield 3), and spelt (WK 86035-8) wheat classes. Digital image analysis (IA) coupled with light microscopy was used to determine starch size distributions where the volume of granules was calculated as spherical particles or oblate spheroids. Starch granules were

J. D. Wilson; D. B. Bechtel; T. C. Todd; P. A. Seib

2006-01-01

462

Application of maximum entropy method for droplet size distribution prediction using instability analysis of liquid sheet  

Microsoft Academic Search

This paper describes the implementation of the instability analysis of wave growth on liquid jet surface, and maximum entropy\\u000a principle (MEP) for prediction of droplet diameter distribution in primary breakup region. The early stage of the primary\\u000a breakup, which contains the growth of wave on liquid–gas interface, is deterministic; whereas the droplet formation stage\\u000a at the end of primary breakup

E. Movahednejad; F. Ommi; S. M. Hosseinalipour; C. P. Chen; S. A. Mahdavi

463

Origin of electric field distribution in organic field-effect transistor: Experiment and analysis  

Microsoft Academic Search

Electric field distribution in the pentacene organic field-effect transistor (OFET) channel is investigated using the microscopic optical second-harmonic generation (SHG). At the on- and off-states of the OFET, enhanced SHG signal was observed near the drain electrode and at the source and drain electrodes. Our analytical analysis indicates that the Laplace field formation is in the off-state of the OFET.

Martin Weis; Takaaki Manaka; Mitsumasa Iwamoto

2009-01-01