Rayleigh Distribution Model Research Articles

Fuzzy Rayleigh Distribution Model for the Expected Salivary Excretion of Oxytocin in Humans

The study isset to investigation the oxytocin was developed bypreset on-line solid-phase micro extraction coupled with liquid chromatography-tandem mass spectrometry in saliva samples using the fuzzy Rayleigh distribution. Parameter of Rayleigh distribution find out by the Maximum Likelihood Estimator.The fuzzy mean values and variance values are calculated for different alpha values. The result shows that the mean and variance values are increasing for lower alpha values and decreasing for upper alpha values.

Research on distribution pattern for central pose errors of 6-degrees of freedom docking mechanism

Central pose errors involving central position error and central orientation error are critical indexes for 6-degrees of freedom docking mechanism assembly quality. The performance of assembly could be evaluated during virtual assembly stage in terms of these indexes. However, the evaluation process for assembly has to employ Monte Carlo simulation, which leads to huge computation cost and usually makes the process impossible. This paper gives an insight of the relation between central pose errors and structural errors and finds that the central position error and central orientation error of docking mechanism conform to Rayleigh distribution model at symmetric pose configuration. In comparison, the maximum difference between results with Rayleigh model-based assembly performance and Monte Carlo simulation-based one is no more than 1.22%. With this model, the evaluation process for assembly performance could be facilitated significantly.

소프트웨어 NHPP 신뢰성모형에 대한 고장시간 예측능력 비교분석 연구

This study aims to analyze the predict capability of some of the popular software NHPP reliability models(Goel-Okumo model, delayed S-shaped reliability model and Rayleigh distribution model). The predict capability analysis will be on two key factors, one pertaining to the degree of fitment on available failure data and the other for its prediction capability. Estimation of parameters for each model was used maximum likelihood estimation using first 80% of the failure data. Comparison of predict capability of models selected by validating against the last 20% of the available failure data. Through this study, findings can be used as priori information for the administrator to analyze the failure of software.

Probability analysis and parameter estimation for nonlinear relative wave motions on a semi-submersible using the method of LH-moments

Nonlinear relative wave motions and air gap performance greatly affect the operation and security of semi-submersibles in harsh environments. An appropriate air gap is essential to preventing potential impact loads, and accurate prediction for long-return-period events is of great concern. Given the random and nonlinear nature of relative wave motions, a reliable approach for their prediction is a challenging task that warrants further research. In this study, a modified three-parameter Rayleigh distribution model for nonlinear relative wave crests was derived utilising a quadratic transformation of incident waves. The method of LH-moments was used to estimate the unknown parameters from sample data, and the relationship between the parameters and LH-moments was derived. The sample data used for the probability analysis were obtained from a model test programme for a semi-submersible. The first-order parameter of the model was found to decrease with increasing η, whereas the second-order parameter was found to increase. A larger second-order parameter indicates higher nonlinearity of the relative wave motions for a 100-year-return sea state than for a 1-year-return sea state. In general, using LH-moments to estimate the parameters of the probability distribution results in better prediction of large relative wave crests with low probabilities of exceedance, because the estimation of the three parameters in the nonlinear Rayleigh model using LH-moments released the constraint on the linear term.

ANN-based evaluation of wind power generation: A case study in Kutahya, Turkey

Wind energy is one of the most significant and rapidly developing renewable energy sources in the world and it provides a clean energy resource, which is a promising alternative in the short term in Turkey. The wind energy potential in various parts of Turkey is becoming economical due to reductions in wind turbine costs, and in fossil fuel atmospheric pollution. This paper is to present, in brief, wind potential in Turkey and to perform an investigation on the wind energy potential of the Kutahya region. A wind measurement station was established at Dumlupinar University Main Campus in order to figure out the wind energy potential in the province. This study analyses the electricity generation capacity of the Kutahya region, Turkey, which uses the wind power system. In the study, the wind data collected from wind measurement stations between July 2001 and June 2004 (36 months) were evaluated to determine the energy potential of the region. Using this energy potential value, the power generation capacity of Kutahya was investigated for 17 different wind turbines. In this analysis, an ANN-based model and Weibull and Rayleigh distribution models were used to determine the power generation. In the ANN model, different feed-forward back propagation learning algorithms, namely Pola-Ribiere Conjugate Gradient, Levenberg–Marquardt and Scaled Conjugate Gradient were applied. The best appropriate model was determined as Levenberg–Marquardt with 15 neurons in a single hidden layer. Using the best ANN topology, it was determined that all the turbines were profitable except turbine type 1. The system with the turbine type 3 was decisively the most profitable case as determined at the end of the study according to Net Present Value concept.

Using speckle statistics to improve attenuation estimates for cervical assessment

Quantitative ultrasound parameters like attenuation can be used to observe microchanges in the cervix. To give a better estimate of attenuation we can use speckle properties to classify which attenuation estimates are valid and conform to the theory. For fully developed and only one type of scatterer, Rayleigh distribution models the signal envelope. But in tissues as the number of scatterer type increases and the speckle becomes unresolved Rayleigh model fails. Gamma distribution has been empirically shown to be the best fit among all the distributions. Since more than one scatterer type is present for our work we used a mixture of gamma distributions. EM algorithm was used to find the parameters of the mixture and on basis of that the tissue types were segmented from each other based on the criteria of different scattering properties. Attenuation estimates were then calculated for tissues of the same scattering type only. 67 Women underwent Transvaginal scan and the attenuation estimates were calculated for them after segregation of tissues on scattering basis. Attenuation was seen to decrease as the time of delivery came closer.

Dynamic Behavior of an Isolated Bridge Pier under Earthquake Effects for Different Soil layers and Support Conditions

An isolated bridge pier having rubber bearings is modeled by finite element technique and dynamic responses under effects of earthquake accelerations are obtained by linear solution methods in time and frequency domain; the results are evaluated by probabilistic distributions. For this purpose, stationary accelerations characterized by Kanai-Tajimi power spectrum are simulated for different soil types and twenty nonstationary records in each soil group are obtained by modulating the amplitudes in harmony with Erzincan NS 1992 component. The pier responses and deck displacements are obtained in time domain for different support and soil conditions by using simulated horizontal and vertical accelerations. Furthermore, variances of the responses are obtained in frequency domain by assuming stationary stochastic behavior and by using power density and cross-power spectra of the applied simultaneous motions. The results are evaluated by those of the time domain solutions and peak responses and variations of peak response factors are determined. For dynamic peak responses, the response quantities corresponding to exceedance probabilities of 2%, 10% and 50% (median) are predicted depending upon soil types by use Rayleigh distribution model

Survival estimation for singly type one censored sample based on generalized Rayleigh distribution

This paper interest to estimation the unknown parameters for generalized Rayleigh distribution model based on censored samples of singly type one . In this paper the probability density function for generalized Rayleigh is defined with its properties . The maximum likelihood estimator method is used to derive the point estimation for all unknown parameters based on iterative method , as Newton – Raphson method , then derive confidence interval estimation which based on Fisher information matrix . Finally , testing whether the current model ( GRD ) fits to a set of real data , then compute the survival function and hazard function for this real data.

Survival estimation for singly type one censored sample based on generalized Rayleigh distribution

This paper interest to estimation the unknown parameters for generalized Rayleigh distribution model based on censored samples of singly type one . In this paper the probability density function for generalized Rayleigh is defined with its properties . The maximum likelihood estimator method is used to derive the point estimation for all unknown parameters based on iterative method , as Newton – Raphson method , then derive confidence interval estimation which based on Fisher information matrix . Finally , testing whether the current model ( GRD ) fits to a set of real data , then compute the survival function and hazard function for this real data.

Deprem Etkisindeki Elastomer Mesnetli Köprü Ayağının Farklı Zemin ve Mesnet Koşullarında Dinamik Davranışı

Dynamic Behavior of Bridge Pier with Elastomeric Bearings under Earthquake Effects for Different Soil layers and Support Conditions An isolated bridge pier having elastomeric bearings is modeled by finite element technique and dynamic responses under the effect of earthquake accelerations which are obtained by linear solution methods in time and frequency domain and the results are evaluated by probabilistic distributions. For this purpose, stationary accelerations characterized by Kanai-Tajimi power spectrum are simulated for different soil types and twenty nonstationary records in each soil group are obtained by modulating the amplitudes in harmony with 1992 Erzincan earthquake NS component. The pier responses and deck displacements are obtained in time domain for different support and soil conditions by using simulated horizontal and vertical accelerations. Furthermore, variances of the responses are obtained in frequency domain by assuming stationary stochastic behavior and by using power density and cross-power spectra of the applied simultaneous motions. The results are evaluated by those of the time domain solutions and peak responses and variations of peak response factors are determined. For dynamic peak responses, the response quantities corresponding to exceedance probabilities of 2%, 10% and 50% (median) are predicted depending upon soil types by use of Rayleigh distribution model

Automatic Segmentation of Antenatal 3-D Ultrasound Images

The development of 3-D ultrasonic probes and 3-D ultrasound (3DUS) imaging offers new functionalities that call for specific image processing developments. In this paper, we propose an original method for the segmentation of the utero-fetal unit (UFU) from 3DUS volumes, acquired during the first trimester of gestation. UFU segmentation is required for a number of tasks, such as precise organ delineation, 3-D modeling, quantitative measurements, and evaluation of the clinical impact of 3-D imaging. The segmentation problem is formulated as the optimization of a partition of the image into two classes of tissues: the amniotic fluid and the fetal tissues. A Bayesian formulation of the partition problem integrates statistical models of the intensity distributions in each tissue class and regularity constraints on the contours. An energy functional is minimized using a level set implementation of a deformable model to identify the optimal partition. We propose to combine Rayleigh, Normal, Exponential, and Gamma distribution models to compute the region homogeneity constraints. We tested the segmentation method on a database of 19 antenatal 3DUS images. Promising results were obtained, showing the flexibility of the level set formulation and the interest of learning the most appropriate statistical models according to the idiosyncrasies of the data and the tissues. The segmentation method was shown to be robust to different types of initialization and to provide accurate results, with an average overlap measure of 0.89 when comparing with manual segmentations.

混响室的混沌特性及其场统计分布

Quantum chaos theory is used to study a reverberation chamber (RC). We evaluate the chaotic characteristics of a numerical RC by analyzing the eigenfrequency spacing distribution with the finite element method. Based on the electromagnetic chaotic features and the hypothesis, the electric field vector eigenfunction in the RC could be expressed as linear superposition of random plane waves. Then the electric field in the RC can be expressed as the vector eigenfunction expansion. The Rayleigh distribution model of probability density function of electric field in the RC is derived by statistical approach. The electric field intensity measurement in an actual mechanical stirring RC is completed with ETS HI-6105 prober. The electric field distribution in the chamber is in close agreement with the result from the statistical model, which proves the validity of the theoretical model.

Research on Public Transit Network Hierarchy Based on Residential Transit Trip Distance

To the problem of being lack of transit network hierarchy theory, a research on public transit network hierarchy optimization based on residential transit trip distance is conducted. Firstly, the hierarchy standard of transit network is given, in addition, both simulating electron cloud model and Rayleigh distribution model are used to fit the residential transit trip distance. Secondly, from the view of balance between supply and demand, the hierarchy step of transit network based on residential transit trip distance is proposed. Then, models of transit’s supply turnover and demand turnover are developed. Finally, the method and models are applied into transit network optimization of Baoding, Hebei, China.

Modeling SAR images with a generalization of the Rayleigh distribution.

Synthetic aperture radar (SAR) imagery has found important applications due to its clear advantages over optical satellite imagery one of them being able to operate in various weather conditions. However, due to the physics of the radar imaging process, SAR images contain unwanted artifacts in the form of a granular look which is called speckle. The assumptions of the classical SAR image generation model lead to a Rayleigh distribution model for the histogram of the SAR image. However, some experimental data such as images of urban areas show impulsive characteristics that correspond to underlying heavy-tailed distributions, which are clearly non-Rayleigh. Some alternative distributions have been suggested such as the Weibull, log-normal, and the k-distribution which had success in varying degrees depending on the application. Recently, an alternative model namely the alpha-stable distribution has been suggested for modeling radar clutter. In this paper, we show that the amplitude distribution of the complex wave, the real and the imaginery components of which are assumed to be distributed by the alpha-stable distribution, is a generalization of the Rayleigh distribution. We demonstrate that the amplitude distribution is a mixture of Rayleighs as is the k-distribution in accordance with earlier work on modeling SAR images which showed that almost all successful SAR image models could be expressed as mixtures of Rayleighs. We also present parameter estimation techniques based on negative order moments for the new model. Finally, we test the performance of the model on urban images and compare with other models such as Rayleigh, Weibull, and the k-distribution.

On quadrature components of dissimilar statistics and their relevance in antenna error analysis

Statistical analysis of the feed array of a complex antenna revealed distribution functions which cannot be represented by Rayleigh or Rice distribution models. Here we present the analytical description of these distributions, which may be seen as an extension of the Rice distribution. We conclude that statistical processes involving guidance of waves with very significant random content (e.g., near nulls) result in general in quadrature components of different statistical properties.

Rayleigh-distribution based minimum error thresholding for SAR images

This paper presents a minimum error thresholding (MET) algorithm under the hypothesis that the gray level histogram of SAR image fits to a mixture model of shifted Rayleigh distribution. This algorithm is applied to real SAR images and compared with traditional Otsu algorithm and other MET algorithms based on various models of histogram. The hypothesis of using Rayleigh distribution model is confirmed by Kolmogorov-Smirnov testing and the comparison results obtained show that the proposed new algorithm has good performance in thresholding SAR images.

Prevalence of hypertension in Mexican-Americans: Robert M. Palmer, University of Southern California School of Medicine, 2025 Zonal Avenue, Los Angeles, California 90033; Jean Mathison; Teresa Walsh

The present study aims to analyze the wind power potential in two locations in Galati county, Romania, before making a decision on the appropriate area for wind turbine installation. The hourly series of wind speed and wind direction were analyzed for the period between January 2017 and December 2018, measured at two meteorological stations of the national network at 10 m height. The Weibull and Rayleigh distribution models were applied to hourly wind speed data to evaluate wind speed characteristics and wind power potentials at wind turbine height. The annual values of k parameter for the Weibull analysis range from 2.15 in 2017 to 2.1 in 2018 for the GL3 site (GL3 — Galati county measurement station number 3, with geographical location: latitude 45.47 N and longitude 28.03 E), while for GL5 site (GL5 — Galati county measurement station number 5, with geographical location: latitude 45.82 N and longitude 27.44 E), the values are 1.33 in 2017 and 1.46 in 2018, respectively. Another important factor in wind resources assessment in addition to the average wind speed is the wind speed distribution in the regime, because two wind turbines installed in two different places (locations that have the same average wind speed), may generate a very different amount of energy, due to differences in wind speed distribution in the two locations. Thus, in 2017, the average annual wind speed at the two locations was approximately the same, being 5.44 m/s at GL3 and 5.41 m/s at GL5, respectively, but the maximum values of power density for the two locations were determined to be 260 W/m2 for GL3 and 361 W/m2 for GL5, in 2017. It was observed that the average annual wind speed was higher than the most frequent wind speed. Another important conclusion is that the greatest influence on the wind power potential has a speed that produces the maximum energy of the wind regime and not the average wind speed or the most frequent wind speed. From the data analysis, it was found that application of the Rayleigh distribution is not suitable for the GL5 case, as the wind speed does not have a normal distribution.