Search results for "weibull distribution"
showing 10 items of 42 documents
Real-time parameter estimation of Zika outbreaks using model averaging
2017
SUMMARYEarly prediction of the final size of any epidemic and in particular for Zika disease outbreaks can be useful for health authorities in order to plan the response to the outbreak. The Richards model is often been used to estimate epidemiological parameters for arboviral diseases based on the reported cumulative cases in single- and multi-wave outbreaks. However, other non-linear models can also fit the data as well. Typically, one follows the so called post selection estimation procedure, i.e., selects the best fitting model out of the set of candidate models and ignores the model uncertainty in both estimation and inference since these procedures are based on a single model. In this…
Reduced reference 3D mesh quality assessment based on statistical models
2015
International audience; During their geometry processing and transmission 3D meshes are subject to various visual processing operations like compression, watermarking, remeshing, noise addition and so forth. In this context it is indispensable to evaluate the quality of the distorted mesh, we talk here about the mesh visual quality (MVQ) assessment. Several works have tried to evaluate the MVQ using simple geometric measures, However this metrics do not correlate well with the subjective score since they fail to reflect the perceived quality. In this paper we propose a new objective metric to evaluate the visual quality between a mesh with a perfect quality called reference mesh and its dis…
Rainfall erosivity over the Calabrian region
1997
Abstract Following the results of a study carried out for the neighbouring Sicilian region, this paper reports a study of the applicability of the annual value, Faj, of the Arnouldus index to represent the erosion risk in Calabrian region. Firstly, By using 214 values of the mean annual value of the erosivity index, FF, and a Kriging interpolation method, an isoerosivity map is plotted. Then, in order to predict the erosion risk for an event of any return period, the probability distribution of the Faj index is studied. An in situ statistical analysis, carried out by using candidate distributions with two parameters (Gauss, LN2, EV1 and Weibull distribution), showed that the EV1 and LN2 law…
Microstructure Design for Fast Lifetime Measurements of Magnetic Tunneling Junctions
2019
The estimation of the reliability of magnetic field sensors against failure is a critical point concerning their application for industrial purposes. Due to the physical stochastic nature of the failure events, this can only be done by means of a statistical approach which is extremely time consuming and prevents a continuous observation of the production. Here, we present a novel microstructure design for a parallel measurement of the lifetime characteristics of a sensor population. By making use of two alternative designs and the Weibull statistical distribution function, we are able to measure the lifetime characteristics of a CoFeB/MgO/CoFeB tunneling junction population. The main param…
White Etching Crack Root Cause Investigations
2014
White etching crack (WEC) failure is distinct to classical fatigue and driven by the composition of lubricants under special loading conditions; for example, slippage and electricity. The white etching area (WEA) within WEC contains carbon supersaturated ferrite (bcc-iron) and carbides, with a size of a few nanometers. This article presents investigations supporting the hypothesis that WEC processes start within a failure-free period by successive accumulation of a structural distortion. This can be measured by acoustic emission. Failure statistics show a steep ascent in the Weibull diagram (s values beyond 1) leading to the assumption that WEC processes start unsuspicious, as one would see…
The Effect of Damage and Geometrical Variability on the Tensile Strength Distribution of Flax Fibers
2010
Natural fibers of plant origin are finding non-traditional applications as reinforcement of composite materials. The mechanical properties of fibers exhibit considerable scatter, being affected by the natural variability in plant as well as the damage accumulated during processing. For bast fibers, the primary damage mode is kink bands – zones of misaligned cellulose microfibrils extending across the fiber and oriented roughly perpendicularly to its axis. Another feature typical for natural fibers and contributing to the scatter of fiber strength is the variability of diameter along a fiber length and among the fibers. An analytical expression for the distribution of the longitudinal tensil…
Threshold Voltage Variability of NROM Memories After Exposure to Ionizing Radiation
2012
Threshold voltage (V-th) behavior of nitride readonly memories (NROMs) was studied after irradiation with photons (gamma-and X-rays), light and heavy ions. Both programmed and nonprogrammed single cells were investigated. The data suggest that two main physical phenomena are contributing to V-th variation and that the V-th loss and the variability can be modeled by a Weibull statistics with a shape parameter k similar to 2.2 regardless of the irradiation species and total dose. The same peculiarities were found in large memory arrays, confirming the results from single-cell studies but with significantly larger statistics. Hence, once the irradiation dose is known, the V-th loss distributio…
Coating fragmentation by branching cracks at large biaxial strain
2007
The fragmentation behaviour of a thin brittle coating attached to a ductile substrate subjected to equibiaxial quasi-static in-plane tension is studied. The experimentally observed cracking patterns are related to repetitively branching coating cracks. The fragmentation process is modelled by the rate equation approach. It is established that fragmentation by branching cracks leads to a qualitatively different fragment distribution compared to binary fragmentation. The fragmentation model is applied to identify crack branching and coating/substrate stress transfer parameters.
Glass fibre strength distribution determined by common experimental methods
2002
The tensile strength of brittle fibres is routinely described by the Weibull distribution. The parameters of the distribution can be obtained from tests on single fibres and fibre bundles or from model composite tests. However, there is growing evidence that the distribution parameters obtained by different experimental techniques differ systematically. In order to investigate the possible causes of such discrepancies, single-fibre tension, fibre bundle, and single-fibre fragmentation tests are employed in this study to obtain strength distribution of commercial E-glass fibres. The results reveal parameter dependence on the approach used to extract the distribution parameters from experimen…
Strength distribution in paper
1998
Abstract Tensile strength distributions are studied in four paper 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 exponential modification of the former are compared with the observations visually and using chi-squared and Kolmogorov–Smirnov tests. The Gumbel distribution fails to fit the data while the Weibull distribution gives satisfactory agreement. However, the double exponential distribution fits the data best, regardless of the ductility of the material.