The Experts below are selected from a list of 199140 Experts worldwide ranked by ideXlab platform

Tadashi Dohi - One of the best experts on this subject based on the ideXlab platform.

  • estimating software Intensity Function based on translation invariant poisson smoothing approach
    IEEE Transactions on Reliability, 2013
    Co-Authors: Xiao Xiao, Tadashi Dohi
    Abstract:

    Because the software failure occurrence process is well-modeled by a non-homogeneous Poisson process, it is of great interest to estimate accurately the software Intensity Function of Non-Homogeneous Poisson Process (NHPP)-based software reliability models (SRM) from observed software-fault count data. In recent years, wavelet-based techniques have been well established in Poisson Intensity estimation because of their technical advantages of computational cost and accuracy. The approach enables us to carry out the analysis of a software debugging process in a nonparametric way. In this paper, we propose an applied Haar wavelet-based approach which is without an approximate data transformation, for software reliability assessment. In a numerical study with real software-fault count data, we compare the proposed estimation method with the previously used data transformation-based estimation method, as well as conventional maximum likelihood estimation and least squares estimation methods. Furthermore, we conduct sensitivity analysis of the resolution level, which affects the estimation accuracy of the proposed method. We also estimate some predictive measures such as software reliability.

  • wavelet shrinkage estimation for non homogeneous poisson process based software reliability models
    IEEE Transactions on Reliability, 2013
    Co-Authors: Xiao Xiao, Tadashi Dohi
    Abstract:

    We develop a novel estimation approach for quantitative software reliability by means of wavelet-based technique, where the underlying software reliability model is described by a non-homogeneous Poisson process. Our approach involves some advantages over the commonly used techniques such as maximum likelihood estimation: 1) the wavelet shrinkage estimation enables us to carry out the time-series analysis with high speed and accuracy requirements; and 2) The wavelet shrinkage estimation is classified into a non-parametric estimation without specifying a parametric form of the software Intensity Function. We consider data-transform-based wavelet shrinkage estimation with four kinds of thresholding schemes for empirical wavelet coefficients to estimate the software Intensity Function. In numerical experiments with real software-fault count data, we show that our wavelet-based estimation methods can provide better goodness-of-fit performance than not only the conventional maximum likelihood estimation and least squares estimation but also the local likelihood estimation method, in many cases, in spite of their non-parametric nature. Furthermore, we investigate the predictive performance of the proposed methods by employing the so-called one-stage look-ahead prediction method, and estimate some predictive measures such as software reliability.

  • PRDC - Estimating Software Intensity Function via Multiscale Analysis and Its Application to Reliability Assessment
    2011 IEEE 17th Pacific Rim International Symposium on Dependable Computing, 2011
    Co-Authors: Xiao Xiao, Tadashi Dohi
    Abstract:

    Since software fault detection process is well-modeled by a non-homogeneous Poisson process, it is of great interest to estimate accurately the Intensity Function from observed software-fault data. In the existing work the same authors introduced the wavelet-based techniques for this problem and found that the Haar wavelet transform provided a very powerful performance in estimating software Intensity Function. In this paper, we also study the Haar-wavelet-transform-based approach to be investigated from the point of view of multiscale analysis. More specifically, a Bayesian multiscale Intensity estimation algorithm is employed. In numerical study with real software-fault count data, we compare the Bayesian multiscale Intensity estimation with the existing non-Bayesian wavelet-based estimation as well as the conventional maximum likelihood estimation method and least squares estimation method.

Adel Hamdi - One of the best experts on this subject based on the ideXlab platform.

  • Detection-Identification of multiple unknown time-dependent point sources in a 2 D transport equation: application to accidental pollution
    Inverse Problems in Science and Engineering, 2016
    Co-Authors: Adel Hamdi
    Abstract:

    We address the nonlinear inverse source problem of identifying multiple unknown time-dependent point sources occurring in a two-dimensional evolution advection–dispersion–reaction equation. Provided to be available within the monitored domain interfaces for recording the generated state and its flux crossing each suspected zone where a source could occur, we establish a constructive identifiability theorem based on an introduced dispersion-current Function that yields uniqueness of the unknown elements defining all occurring sources. Then, the established theorem leads to develop a detection-identification method that goes throughout the monitored domain to detect in each suspected zone whether there exists or not an occurring source. Once a source is detected, the developed method determines lower and upper bounds of the mean value discharged by its unknown time-dependent Intensity Function. Thereafter, the method localizes the sought position of the detected source as the unique solution of an equation satisfied by the introduced dispersion-current Function and identifies its unknown Intensity Function from solving an associated deconvolution problem. Ultimately, the unknown number of occurring sources is deduced as the sum of all detected-identified active sources. Some numerical experiments on a variant of the surface water BOD pollution model are presented.

  • Inverse source problem in a 2D linear evolution transport equation: detection of pollution source
    Inverse Problems in Science and Engineering, 2012
    Co-Authors: Adel Hamdi
    Abstract:

    This article deals with the identification of a time-dependent source spatially supported at an interior point of a 2D bounded domain. This source occurs in the right-hand side of an evolution linear advection-dispersion-reaction equation. We address the problem of localizing the source position and recovering the history of its time-dependent Intensity Function. We prove the identifiability of the sought source from recording the state on the outflow boundary of the controlled domain. Then, assuming the source Intensity Function vanishes before reaching the final control time, we establish a quasi-explicit identification method based on some exact boundary controllability results that enable to determine the elements defining the sought source using the records of the state on the outflow boundary and of its flux on the inflow boundary. Some numerical experiments on a variant of the surface water biological oxygen demand pollution model are presented.

  • Identification of a time-varying point source in a system of two coupled linear diffusion-advection- reaction equations: application to surface water pollution
    Inverse Problems, 2009
    Co-Authors: Adel Hamdi
    Abstract:

    This paper deals with the identification of a point source (localization of its position and recovering the history of its time-varying Intensity Function) that constitutes the right-hand side of the first equation in a system of two coupled 1D linear transport equations. Assuming that the source Intensity Function vanishes before reaching the final control time, we prove the identifiability of the sought point source from recording the state relative to the second coupled transport equation at two observation points framing the source region. Note that at least one of the two observation points should be strategic. We establish an identification method that uses these records to identify the source position as the root of a continuous and strictly monotonic Function. Whereas the source Intensity Function is recovered using a recursive formula without any need of an iterative process. Some numerical experiments on a variant of the surface water pollution BOD–OD coupled model are presented.

  • The recovery of a time-dependent point source in a linear transport equation: application to surface water pollution
    Inverse Problems, 2009
    Co-Authors: Adel Hamdi
    Abstract:

    The aim of this paper is to localize the position of a point source and recover the history of its time-dependent Intensity Function that is both unknown and constitutes the right-hand side of a 1D linear transport equation. Assuming that the source Intensity Function vanishes before reaching the final control time, we prove that recording the state with respect to the time at two observation points framing the source region leads to the identification of the source position and the recovery of its Intensity Function in a unique manner. Note that at least one of the two observation points should be strategic. We establish an identification method that determines quasi-explicitly the source position and transforms the task of recovering its Intensity Function into solving directly a well-conditioned linear system. Some numerical experiments done on a variant of the water pollution BOD model are presented.

Xiao Xiao - One of the best experts on this subject based on the ideXlab platform.

  • QRS Companion - Software Intensity Function Prediction by Haar Wavelet Regression
    2015 IEEE International Conference on Software Quality Reliability and Security - Companion, 2015
    Co-Authors: Xiao Xiao
    Abstract:

    This paper proposes a semi-parametric model to predict the software Intensity Function of NHPP-based SRM. Haar wavelet is used to extract the features of the software Intensity Function from the observed software fault count data, and a simple quadratic Function is used to predict the trend of the Haar coefficients. The prediction of the software Intensity Function is achieved by applying inverse Haar wavelet transform to the predicted Haar coefficients.

  • estimating software Intensity Function based on translation invariant poisson smoothing approach
    IEEE Transactions on Reliability, 2013
    Co-Authors: Xiao Xiao, Tadashi Dohi
    Abstract:

    Because the software failure occurrence process is well-modeled by a non-homogeneous Poisson process, it is of great interest to estimate accurately the software Intensity Function of Non-Homogeneous Poisson Process (NHPP)-based software reliability models (SRM) from observed software-fault count data. In recent years, wavelet-based techniques have been well established in Poisson Intensity estimation because of their technical advantages of computational cost and accuracy. The approach enables us to carry out the analysis of a software debugging process in a nonparametric way. In this paper, we propose an applied Haar wavelet-based approach which is without an approximate data transformation, for software reliability assessment. In a numerical study with real software-fault count data, we compare the proposed estimation method with the previously used data transformation-based estimation method, as well as conventional maximum likelihood estimation and least squares estimation methods. Furthermore, we conduct sensitivity analysis of the resolution level, which affects the estimation accuracy of the proposed method. We also estimate some predictive measures such as software reliability.

  • wavelet shrinkage estimation for non homogeneous poisson process based software reliability models
    IEEE Transactions on Reliability, 2013
    Co-Authors: Xiao Xiao, Tadashi Dohi
    Abstract:

    We develop a novel estimation approach for quantitative software reliability by means of wavelet-based technique, where the underlying software reliability model is described by a non-homogeneous Poisson process. Our approach involves some advantages over the commonly used techniques such as maximum likelihood estimation: 1) the wavelet shrinkage estimation enables us to carry out the time-series analysis with high speed and accuracy requirements; and 2) The wavelet shrinkage estimation is classified into a non-parametric estimation without specifying a parametric form of the software Intensity Function. We consider data-transform-based wavelet shrinkage estimation with four kinds of thresholding schemes for empirical wavelet coefficients to estimate the software Intensity Function. In numerical experiments with real software-fault count data, we show that our wavelet-based estimation methods can provide better goodness-of-fit performance than not only the conventional maximum likelihood estimation and least squares estimation but also the local likelihood estimation method, in many cases, in spite of their non-parametric nature. Furthermore, we investigate the predictive performance of the proposed methods by employing the so-called one-stage look-ahead prediction method, and estimate some predictive measures such as software reliability.

  • PRDC - Estimating Software Intensity Function via Multiscale Analysis and Its Application to Reliability Assessment
    2011 IEEE 17th Pacific Rim International Symposium on Dependable Computing, 2011
    Co-Authors: Xiao Xiao, Tadashi Dohi
    Abstract:

    Since software fault detection process is well-modeled by a non-homogeneous Poisson process, it is of great interest to estimate accurately the Intensity Function from observed software-fault data. In the existing work the same authors introduced the wavelet-based techniques for this problem and found that the Haar wavelet transform provided a very powerful performance in estimating software Intensity Function. In this paper, we also study the Haar-wavelet-transform-based approach to be investigated from the point of view of multiscale analysis. More specifically, a Bayesian multiscale Intensity estimation algorithm is employed. In numerical study with real software-fault count data, we compare the Bayesian multiscale Intensity estimation with the existing non-Bayesian wavelet-based estimation as well as the conventional maximum likelihood estimation method and least squares estimation method.

James C. Saunders - One of the best experts on this subject based on the ideXlab platform.

  • Distribution of rate–Intensity Function types in chick cochlear nerve after exposure to intense sound
    Brain Research, 1999
    Co-Authors: Stefan K.r. Plontke, Jonathan Lifshitz, James C. Saunders
    Abstract:

    Intense sound exposure to the chick ear produces cochlear damage and losses in auditory Function. At twelve days post exposure there is considerable structural repair, although a defect on the sensory epithelium remains in the form of an incompletely healed 'patch' lesion. Auditory Function significantly recovers 12 days after the exposure, but it, too, is incomplete. In this paper we describe the relationship between stimulus Intensity and cochlear nerve discharge rate (the rate-Intensity Function) in two groups of chicks. One is exposed to damaging sound levels but allowed 12 days to recover, while the other is a group of non-exposed and age-matched control animals. Three different types of rate-Intensity Functions were identified; saturating, sloping, and straight. The percentage of saturating and sloping Functions was compared across all characteristic frequencies in both groups of animals. A significant change was observed in the distribution of these types for recovered units with characteristic frequencies within the region of the patch lesion. In addition, the rate-Intensity Functions of these units exhibited a steeper slope and a higher maximum response. The distribution of rate-Intensity Function types and their slope and maximum responses, for units with characteristic frequencies outside of the patch lesion, was similar to those found in control ears. The changes in the cochlear nerve response in exposed chicks may be due to alterations in cochlear mechanics, hair cell or synaptic membrane properties, hair cell innervation, or the loss of a tonic suppression of afferent activity exerted by the damaged short hair cells.

M. S. Aminzadeh - One of the best experts on this subject based on the ideXlab platform.