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Stochastic RUL Calculation Enhanced With TDNN-Based IGBT Failure Modeling

IEEE TRANSACTIONS ON RELIABILITY 2016年第2期65卷 558-573页

作者： Alghassi, Alireza Perinpanayagam, Suresh Samie, Mohammad Cranfield Univ Sch Aerosp Transport & Mfg Bedford MK43 0A1 England

Power electronics are widely used in the transport and energy sectors. Hence, the reliability of these power electronic components is critical to reducing the maintenance cost of these assets. It is vital that the health of these components is monitored for increasing the safety and availability of a system. The aim of this paper is to develop a prognostic technique for estimating the remaining useful life (RUL) of power electronic components. There is a need for an efficient prognostic algorithm that is embeddable and able to support on-board real-time decision-making. A time delay neural network (TDNN) is used in the development of failure modes for an insulated gate bipolar transistor (IGBT). Initially, the time delay neural network is constructed from training IGBTs' ageing samples. A stochastic process is performed for the estimation results to compute the probability of the health state during the degradation process. The proposed TDNN fusion with a statistical approach benefits the probability distribution function by improving the accuracy of the results of the TDDN in RUL prediction. The RUL (i.e., mean and confidence bounds) is then calculated from the simulation of the estimated degradation states. The prognostic results are evaluated using root mean square error (RMSE) and relative accuracy (RA) prognostic evaluation metrics.

关键词： Insulated gate bipolar transistor (IGBT) power electronics prognostics probability distribution function remaining useful life (RUL) time-delay neural network

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Fluctuation of mean Lyapunov exponent for Kuramoto-Sivashinsky equation

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PHYSICA A 2000年第3-4期285卷 325-331页

作者： Shibata, H Sojo Univ Dept Gen Educ Kumamoto 8600082 Japan

The statistical aspect of Lyapunov exponent for Kuramoto-Sivashinsky equation is studied. Fluctuation of mean Lyapunov exponent is given by the probability distribution function of its time coarse grained quantity, local Lyapunov exponent. The functional form of the probability distribution function is obtained. Its form is different from the one obtained from the large deviation statistics. Also, the relation between the damping constant included in Kuramoto-Sivashinsky equation and Lyapunov exponent is obtained. (C) 2000 Elsevier Science B.V. All rights reserved.

关键词： mean Lyapunov exponent local Lyapunov exponent Kuramoto-Sivashinsky equation probability distribution function

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Experimental and probabilistic analysis of distal femoral periprosthetic fracture: a comparison of locking plate and intramedullary nail fixation. Part B: probabilistic investigation

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COMPUTER METHODS IN BIOMECHANICS AND BIOMEDICAL ENGINEERING 2011年第2期14卷 175-182页

作者： Salas, Christina Mercer, Deana DeCoster, Thomas A. Taha, Mahmoud M. Reda Univ New Mexico Dept Mech Engn Albuquerque NM 87131 USA Univ New Mexico Dept Civil Engn Albuquerque NM 87131 USA 1 Univ New Mexico Univ New Mexico Hosp Dept Orthopaed & Rehabil Albuquerque NM 87131 USA

The following is Part B of a two-part study. Part A evaluated, biomechanically, intramedullary (IM) nails versus locking plates for fixation of an extra-articular, metaphyseal wedge fracture in synthetic osteoporotic bone. Part B of this study introduces deterministic finite element (FE) models of each construct type in synthetic osteoporotic bone and investigates the probability of periprosthetic fracture of the locking plate compared with the retrograde IM nail using Monte Carlo simulation. Deterministic FE models of the fractured femur implanted with IM nail and locking plate, respectively, were developed and validated using experimental data presented in Part A of this study. The models were validated by comparing the load-displacement curve of the experimental data with the load-displacement curve of the FE simulation with a root-mean square error of less than 3mm. The validated FE models were then modified by defining the cortical and cancellous bone modulus of elasticity as uncertain variables that could be assumed to vary randomly. Monte Carlo simulation was used to evaluate the probability of fracture (POF) of each fixation. The POF represents the cumulative probability that the predicted shear stresses in the cortical bone will exceed the expected shear strength of the cortical bone. This investigation provides information regarding the significance of post-operative damage accumulation on the POF of the implanted bones when the two fixations are used. The probabilistic analysis found the locking plate fixation to have a higher POF than the IM nail fixation under the applied loading conditions (locking plate 21.8% versus IM nail 0.019%).

关键词： osteoporosis probabilistic analysis Monte Carlo simulation cumulative distribution function probability distribution function

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FLOW REGIME IDENTIFICATION IN CRYOGENIC GAS-LIQUID FLOW-THROUGH VERTICAL TUBES

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CRYOGENICS 1995年第6期35卷 393-398页

作者： DAS, R PATTANAYAK, S Cryogenic Engineering Centre Indian Institute of Technology Kharagpur-721302 India

A method of identifying flow regimes in gas-liquid two-phase flow of cryogenic fluids through vertical tubes has been developed. In this method a small capacitor is used to sense the local void fraction of the flowing mixture. The capacitor is connected to a multivibrator whose pulse width is modulated in response to the changing void fraction. The pulse width is digitized after deducting its stray portion. It is seen that the probability distribution function (PDF) of the digitized pulse width data shows some unique features in different flow regimes. This technique has been used principally to overcome difficulties in detecting the fractional change of a very small capacitance of the void fraction sensor used in monitoring gas-liquid two-phase flow of nitrogen.

关键词： 2-PHASE FLOW FLOW REGIMES CAPACITANCE SENSOR PULSE WIDTH MODULATION probability distribution function

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Waves plus currents crossing at a right angle: near-bed velocity statistics

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JOURNAL OF HYDRAULIC RESEARCH 2018年第4期56卷 464-481页

作者： Faraci, C. Scandura, P. Musumeci, R. E. Foti, E. Univ Messina Dept Engn I-98166 S Agata ME Italy Univ Catania Dept Civil Engn & Architecture Vle A Doria 6 I-95125 Catania Italy

Wave-current flow over a bottom covered with different roughness elements was analysed to provide new insights into the statistical properties of the near-bed velocity. Experimental data of three different experimental campaigns, with orthogonal waves and currents over a sandy bed, a gravel bed and a rippled bed were used. Velocity profiles were acquired by means of a micro-ADV. The paper focuses on the effects that the waves have on the statistics of the velocity in the current direction. In particular, in the case of a steady current only, the near-bed velocities closely follow a Gaussian distribution. When waves are added, the distribution becomes double-peaked. In order to get single-peaked velocity distributions the total velocity events in the current direction were split in two classes according to the sign of the wave directed velocities. The nature of the distribution functions is influenced by the mass conservation principle and, in the rippled bed case, by the vorticity dynamics.

关键词： Bed roughness higher-order statistics probability distribution function ripples wave boundary layer wave-current interaction

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Optimal wind energy penetration in power systems: An approach based on spatial distribution of wind speed

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ENERGY CONVERSION AND MANAGEMENT 2016年 118卷 387-398页

作者： Zolfaghari, Saeed Riahy, Gholam H. Abedi, Mehrdad Golshannavaz, Sajjad Amirkabir Univ Technol Dept Elect Engn Tehran Iran Urmia Univ Dept Elect Engn Orumiyeh Iran

Contributing in power system expansions, the present study establishes an efficient scheme for optimal integration of wind energy resources. The proposed approach highly concerns the spatial distribution of wind speed at different points of a wind farm. In mathematical statements, a suitable probability distribution function (PDF) is well-designed for representing such uncertainties. In such conditions, it is likely to have dissimilar output powers for individual and identical wind turbines. Thus, the overall aggregated PDF of a wind farm remarkably influences the critical parameters including the expected power and energy, capacity factor, and the reliability metrics such as loss of load expectation (LOLE) and expected energy not supplied (EENS). Furthermore, the proposed approach is deployed for optimal allocation of wind energy in bulk power systems. Hence, two typical test systems are numerically analyzed to interrogate the performance of the proposed approach. The conducted survey discloses an over/underestimation of harvestable wind energy in the case of overlooking spatial distributions. Thus, inaccurate amounts of wind farm's capacity factor, output power, energy and reliability indices might be estimated. Meanwhile, the number of wind turbines may be misjudged to be installed. However, the proposed approach yields in a fair judgment regarding the overall performance of the wind farm. Consequently, a reliable penetration level of wind energy to the power system is assured. Extra discussions are provided to deeply assess the promising merits of the founded approach. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Spatial distribution of wind speed Wind farm's output power probability distribution function Reliability indices Optimal expansion planning

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Probabilistic analysis of stress concentration factors in tubular KT-joints reinforced with internal ring stiffeners under in-plane bending loads

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THIN-WALLED STRUCTURES 2016年 99卷 58-75页

作者： Ahmadi, Hamid Yeganeh, Ali Mohammadi, Amir Hossain Zavvar, Esmaeil Univ Tabriz Fac Civil Engn Tabriz *** Iran Sharif Univ Technol Dept Civil Engn Tehran Iran

In the present research, results from the finite element (FE) stress analysis of 108 models, validated using test data obtained from the experimental investigation, was used to propose probability distribution models for stress concentration factors (SCFs) in internally ring-stiffened tubular KT-joints under four types of in-plane bending (IPB) loads. The SCF is one of the crucial parameters in the fatigue reliability analysis of tubular joints. It exhibits considerable scatter which calls for greater emphasis in accurate derivation of its governing probability function. According to the knowledge of the authors, no comprehensive research has been carried out on the probability distribution of SCF5 especially in stiffened tubular joints commonly found in offshore structures. What has been used so far as the probability distribution of SCFs in the reliability analysis of this type of joints is mainly based on assumptions and limited observations, especially in terms of distribution parameters. Based on a FE parametric study, a set of sample databases was prepared for the maximum central- and outer-brace SCF5;and density histograms were generated for these samples. Nine different probability density functions (PDFs) were fitted to these histograms. The maximum likelihood method was used to compute the parameters of fitted distributions. In each case, using a developed computer code, Kolmogorov-Smirnov and chi-squared tests were applied to evaluate the goodness of fit. Finally, the best-fitted distributions were selected and after substituting the values of estimated parameters for each distribution, six fully defined PDFs were developed for the maximum weld-toe SCF5 of central and outer braces in internally ring-stiffened tubular KT-joints subjected to four different types of IPB loading. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Ring-stiffened tubular KT-joint In-plane bending (IPB) Stress concentration factor (SCF) probability distribution function Kolmogorov-Smirnov test Chi-squared goodness-of-fit test

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A tool for determining urban emission characteristics to be used in exposure assessment

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ENVIRONMENT INTERNATIONAL 2010年第3期36卷 281-289页

作者： Kassomenos, P. Lykoudis, S. Chaloulakou, A. Univ Ioannina Dept Phys GR-45110 Ioannina Greece Inst Environm Res & Sustainable Dev Natl Observ Athens GR-15236 Athens Greece Natl Tech Univ Athens Sch Chem Engn GR-15780 Athens Greece

The exposure of citizens to elevated air pollution concentrations is one of the major factors leading to the deterioration of the quality of life and possibly to health problems in urban areas. The concentration of air pollutants depends largely on pollutant emission levels. If the statistical probability distribution function of the concentration of an air pollutant is known, it is possible to estimate how many times this concentration exceeds the air quality standards, or estimate changes in the emission levels in an area. It can be also used to estimate the long term exposure of population to certain pollutants. In this paper fifteen theoretical probability distribution functions, were used to fit the actual concentration frequency distributions of CO, NO(2), O(3). SO(2), and Black Smoke (BS) in Athens, Greece for a 23-year period. The results showed that the theoretical distribution type best describing the distribution of the pollutants is Inverse Gaussian followed by the Extreme value distribution. The number of exceedances of air quality limits was used to validate the performance of the theoretical distributions that were best fitted to the observed ones. The temporal evolution of emission strength was estimated through the temporal evolution of the parameters of the probability distribution functions. Missing periods were accounted for by estimating the respective distribution functions through interpolation or extrapolation from the existing ones. The derived variation of emission levels consistently represents the emission reduction strategies enforced over the years, as well as the escalating growth of the passenger car fleet volume, and could be a useful tool for the design and assessment of emission control strategies. (C) 2009 Elsevier Ltd. All rights reserved.

关键词： Air pollution probability distribution function Exposure assessment Emission reduction Exceedances

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Wind energy feasibility and wind turbine selection studies for the city Surat,India

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Clean Energy 2024年第3期8卷 166-173页

作者： Arshi Banu P S Maanat Bhadani Hindustan Institute of Technology and Science ChennaiIndia The Doon School UttarakhandDehradunIndia

Wind energy represents a clean,abundant and cost-effective power source,fostering job growth and environmental *** wind energy harnesses several gigawatts today,its availability hinges on diverse factors,with geographical location standing *** turbines,with varying capacity ranges,saturate the *** site-specific suitability and matching the appropriate turbine to meet specific requirements are of paramount *** study aims to assess the feasibility of wind energy in Surat,Gujarat,India and select an optimal small commercial turbine for residential *** research involves Rayleigh and Weibull probability distribution functions based on yearlong velocity *** distributions are fitted with actual data,revealing the most probable velocity(v_(mf)=3 m/s)and velocity at maximum power(v_(pmax)=5 m/s).The power availability of the site has been assessed as 42.6 W/m^(2)using both graphical and analytical *** commercial turbines have been shortlisted based on on-site power criteria and their specifications are evaluated against site power availability.A comparative analysis culminates in identifying the most suitable turbine for the *** best suitable turbine for the site with an annual energy yield of 8 MW has been suggested amongst selected turbines for small-scale residential applications.

关键词： site feasibility wind energy commercial wind turbine probability distribution function rated power

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Comparative analysis of Weibull parameters for wind data measured from met-mast and remote sensing techniques

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RENEWABLE ENERGY 2018年 115卷 1153-1165页

作者： Chaurasiya, Prem Kumar Ahmed, Siraj Warudkar, Vilas MANIT Dept Mech Engn Bhopal MP India

The remote sensing techniques are gaining attention worldwide for the comprehensive assessment of wind resource in flat, complex, and mountainous terrain. This paper presents an attempt to increase the confidence on remote sensing technique to compute Weibull parameters at higher heights for assessment of wind energy resource. The measurement campaign was conducted at Kayathar, Tamil Nadu, India. The 10 min average time series wind speed data for the period of one month (September 2014) were recorded simultaneously at 80 m and 100 m using cup anemometer installed in the proximity of 120 m meteorological mast, Second Wind Triton SODAR (Sound Detection and Ranging) and Continuous wave wind LIDAR (Light Detection and Ranging). The data obtained from this measurement were analyzed and Weibull parameters were evaluated using nine different methods. The applicability of nine methods for calculation of Weibull parameters is analyzed based on statistical analysis i.e. Root Mean Square Error Test, Coefficient of Determination, Mean Absolute Percentage Error, and Chi-square Test for both measuring techniques. This study also shows the performance of remote sensing technology by comparing with result obtained from met mast. The outcome of this study is expected to encourage the deployment of remote sensing techniques at Indian sites. (C) 2017 Published by Elsevier Ltd.

关键词： Weibull parameters Wind frequency distribution Wind speed probability distribution function Statistical analysis

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