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Statistical approach using phase variance for analysing correlated multipath fading environment

IET COMMUNICATIONS 2018年第8期12卷 948-955页

作者： Dhaka, Arvind Bhaskar, Vidhyacharan Nandal, Amita Marina, Ninoslav Natl Inst Technol Comp Sci & Engn Dept Hamirpur Himachal Prades India San Francisco State Univ Dept Elect & Comp Engn 1600 Holloway Ave San Francisco CA 94132 USA Univ Informat Sci & Technol Ohrid North Macedonia

In this study, the authors present an infinite-series-based approach for the performance analysis of n-diversity receivers operating over Rayleigh correlated fading channels in the presence of correlated phase difference. The performance analysis is based on error probability and signal-to-noise ratio (SNR) criteria. The authors propose a model to investigate the impact of phase difference between n-correlated Rayleigh fading channels. We have derived the closed form expression for phase distribution in a Rayleigh fading environment with the help of some statistical properties. The authors have also derived the joint density function of phase difference and its associated correlated envelopes. With the help of probability distribution function, the authors have observed two cases of equally spaced and loosely spaced antennas and showed that imperfect phase estimation lowers the SNR. The authors also present statistical analysis and the effectiveness of the proposed approximation to predict the variance of the phase difference. The authors have performed Monte Carlo simulation for a subcarrier-based spectrum to analyse error probability with respect to phase and correlation.

关键词： statistical distributions Rayleigh channels antennas phase estimation Monte Carlo methods statistical approach correlated multipath fading environment analysis infinite-series-based approach n-diversity receiver correlated phase difference error probability SNR signal-to-noise ratio n-correlated Rayleigh correlated fading channel joint density function probability distribution function antenna imperfect phase estimation Monte Carlo simulation subcarrier-based spectrum

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Risk assessment of distribution coefficient from ¹³⁷Cs measurements

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ENVIRONMENTAL MONITORING AND ASSESSMENT 2009年第1-4期149卷 363-370页

作者： Kulahci, Fatih Sen, Zekai Firat Univ Dept Phys Fac Sci & Arts TR-23169 Elazig Turkey Istanbul Tech Univ Hydraul & Water Resources Dept Fac Civil Engn TR-34469 Istanbul Turkey

Classically distribution coefficient is defined as the ratio of solid total element concentration to surface water total concentration. This coefficient is obtained from the ion measurements in the Keban Dam, Turkey, which supplies water for domestic, irrigation and hydroelectric energy generation purposes. The measurements of Cs-137 are carried out in 40 different sites and the general risk formulation and application is achieved for the distribution coefficient. The models are of exponential type and the spatial independence of the data is considered. Various charts are prepared for a set of risk levels as 5%, 10%, 20%, 25%, and 50%.

关键词： probability distribution function Radionuclide Risk assessment Stochastic model Water

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Probabilistic load flow computation using the method of combined cumulants and Gram-Charlier expansion

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IEEE TRANSACTIONS ON POWER SYSTEMS 2004年第1期19卷 676-682页

作者： Zhang, P Lee, ST Elect Power Res Inst Palo Alto CA 94304 USA

Open access transmission has created a deregulated power market and brought new challenges to system planning. This paper proposes a new method to compute a probabilistic load flow in extensive power systems for the purpose of using it as a quick screening tool to determine the major investment on improving transmission system inadequacy. This innovative method combines the concept of Cumulants and Gram-Charlier expansion theory to obtain probabilistic distribution functions of transmission line flows. It has significantly reduced the computational time while maintaining a high degree of accuracy. This enables probabilistic analysis of power flow problems to be treated objectively and allows quantitative assessment of system reliability.

关键词： cumulants Gram-Charlier expansion open access transmission and deregulated power market power system probabilistic load flow probability distribution function transmission planning

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Regional analysis of the annual maximum daily rainfall in the province of Malaga (southern Spain) using the principal component analysis

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WATER AND ENVIRONMENT JOURNAL 2011年第4期25卷 522-531页

作者： Garcia-Marin, A. P. Ayuso-Munoz, J. L. Taguas-Ruiz, E. V. Estevez, J. Univ Cordoba Dept Rural Engn E-14080 Cordoba Spain

The flood and drought cycles suffered of old by the province of Malaga, the variability in the distribution of rainfall throughout the province and the reduced length of the data series make it of interest to carry out a regional analysis (RA) of the yearly maximum daily precipitation data to obtain appropriate rainfall quantiles. By taking these maximum precipitations values from 72 weather stations, and their physiographic parameters latitude and altitude, four regions with similar rainfall patterns have been determined by the principal component analysis statistical technique. Then, carrying out an RA of the yearly maximum daily precipitations for each of the regions discriminated, it was observed that three of them were homogeneous for the parameter being studied. In those homogeneous regions that grouped data of different stations but close rainfall pattern, frequency curves could be calculated for several return periods by means of the functions that best fit the data of each region. With these regional curves, it has been possible to obtain more accurate values of the maximum daily quantiles for each of the stations analysed than through the conventional local frequency analysis.

关键词： homogeneous region probability distribution function rainfall regional frequency analysis

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NONPARAMETRIC ONE-SIDED CONFIDENCE-INTERVALS FOR AN UNKNOWN distribution function USING CENSORED-DATA

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TECHNOMETRICS 1985年第1期27卷 41-48页

作者： SANDFORD, MD Operational Research and Statistics Group Royal Military College of Science Shrivenham Swindon SN6 8LA United Kingdom

Nonparametric one-sided intervals for an unknown distribution function are developed here. They include those based on the Kolmogorov-Smirnov test, but they are more flexible; they can be calculated for censored samples, and they do not necessarily include zero or unity at the extremes of the data. When used as confidence limits on the reliability function for lifetime data, they allow nontrivial confidence limits even at the lifetime of the oldest item.

关键词： Tolerance limits Confidence interval probability distribution function Censored sample Order statistics Reliability function

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Circuit and noise analysis of odorant gas sensors in an E-nose

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SENSORS 2005年第1-2期5卷 85-96页

作者： Tian, FC Yang, SX Dong, K Univ Guelph Sch Engn Guelph ON N1G 2W1 Canada Chongqing Univ Coll Commun Engn Chongqing 400044 Peoples R China

In this paper, the relationship between typical circuit structures of gas sensor circuits and their output noise is analyzed. By using averaged segmenting periodical graph and improved histogram estimation methods, we estimated their noise power spectra and optimal probability distribution functions (pdf). The results were confirmed through experiment studies.

关键词： gas sensor circuit noise power spectrum probability distribution function

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Experimental comparison of flow pattern detection techniques for air-water mixture flow

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EXPERIMENTAL THERMAL AND FLUID SCIENCE 1999年第1期19卷 1-12页

作者： Keska, JK Williams, BE St Martins Coll Dept Engn Mech Tumwater WA 98501 USA St Martins Coll Dept Engn Mech Rainier WA 98576 USA

The complicated and complex nature of two-phase mixture flow phenomenon itself requires detection, monitoring and description of flow pattern influence on the dynamic parameters of mixture flow. The experimental research documentation and control of real mixture flow requires detection, monitoring and measurement of many parameters associated with concentration, velocity and pressure with their distributions in time and space. In addition to the complexity of two-phase mixture flow, there is difficulty in comparing results of experiments from different publications due to the limitation in documentation in the used measurement techniques as well as experimental methodologies. Four often-used measurement methods for flow pattern detection were identified, developed and implemented in the constructed vertical experimental system. This computer-aided experimental system (CAES) was used to generate all typical flow patterns in vertical flow and measure all chosen dynamic parameters (concentration, pressure, and interfacial phenomenon) simultaneously. In this CAES the flow pattern detection system is composed of the application of two different electromagnetic methods (capacitive and resistive), pressure fluctuation method and an optical method. In the reported experimental research on vertical adiabatic air-water flow, results were obtained using all four chosen measurement methods simultaneously. The results allowed a direct comparison of the efficiency of each method in terms of individual ability and sensitivity in the detection of flow patterns. The different sensitivity and abilities of individual methods to detect flow patterns were documented and discussed. (C) 1999 Elsevier Science Inc. All rights reserved.

关键词： void fraction concentration two-phase flow heterogeneous mixture statistical analysis probability distribution function flow pattern capacitive resistive pressure optical sensor computer-aided system fluctuation random fluctuation detection system experimental system concomitant method experimental data air-water mixture

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Simulation of the fiber orientation through a finite element approach to solve the Fokker-Planck equation

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JOURNAL OF NON-NEWTONIAN FLUID MECHANICS 2024年 331卷

作者： Al Ayoubi, Nazih Assaad Digonnet, Hugues Silva, Luisa Binetruy, Christophe Renault, Thierry Comas-Cardona, Sebastien Nantes Univ Inst Rech Genie Civil & Mecan GeM CNRS Ecole Cent NantesUMR 6183 1 Rue Noe F-44321 Nantes France FORVIA 14 Rue Petits Bois F-35400 St Malo France

This work aims to introduce a groundbreaking approach by directly computing the Fokker-Planck equation, providing a mesoscopic scale orientation indicator based on the 2D-probability density function (PDF) of the fibers' orientation state. Unlike conventional methods that rely on pre-averaged quantities and closure approximations, our method offers enhanced accuracy and information preservation. The model's enhanced accuracy can be served as a foundational tool for future studies, enabling the development of comprehensive models describing the fluid-flow coupling problem with precision. Consequently, this advancement facilitates the simulation of real-case scenarios, such as the dynamic motion of fibers during the injection phase of molten thermoplastics within a mold cavity. The novelty of this work lies in its application of the Streamline-Upwind/Petrov-Galerkin (SUPG) finite element method, on both orientation and physical spaces. Our model shows the potential to improve the understanding and prediction of fiber behavior in industrial applications, offering valuable insights into process optimization and design. Implemented within a finite element framework, a comprehensive investigation is conducted into the effects of mesh refinement, time scheme, and time stepping on the computational modeling of the PDF evolution, aiming to strike an optimal balance between model precision and computational efficiency. The validation tests were conducted for the case of simple shear flow to examine the influence of the interaction coefficient C-I and the fiber shape factor lambda on the resolution of the probability distribution function. The numerical results demonstrate the evolution of fiber orientation over time under Poiseuille flow conditions.

关键词： Fiber orientation probability distribution function Fokker-Planck equation Finite element method Numerical modeling

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A multiparametric study for size and stability of hybrid Fe2O3-NiO nanoparticles and their statistical transformation

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PARTICULATE SCIENCE AND TECHNOLOGY 2024年第7期42卷 1282-1301页

作者： Usman, Muhammad Sarfraz, Ambreen Shafaat, Shanza Hussain, Nasira Khan, Asad Muhammad Hussain, Zakir Amin, Bilal Ahmad Zafar Shaikh, Ahson Jabbar COMSATS Univ Islamabad Dept Chem Abbottabad Campus Abbottabad Kpk Pakistan COMSATS Univ Islamabad Dept Math Abbottabad Campus Abbottabad Kpk Pakistan COMSATS Univ Islamabad Energy Res Ctr Lahore Campus Lahore Punjab Pakistan

Bimetallic mixed metal oxide hybrid nanoparticles of iron and nickel are prepared via the co-precipitation method and are characterized by various techniques. Optimization of these nanoparticles involves finding the optimal synthetic conditions and parameters to achieve the hybrid material's desired size, stability, and composition. The effects of the ratio of precursor salts, time of addition of reactant, pH, and the temperature for the synthesis of these mixed oxide nanoparticles are investigated. Concentration studies revealed successful synthesis of the hybrids with the controlled smallest size, at equal concentrations of precursor salts. pH and time of addition of reactant studies revealed the synthesis of least-sized hybrids at pH 13 and at a slow mode of addition of reactant. The optimal temperature at which hybrid nanoparticles are found at the smallest controlled size is 40 degrees C, whereas increasing temperature causes an increase in the size of nanoparticles. The hydrodynamic size and zeta potential studies are also evaluated through statistical models including probability distribution function and grow-decay model, revealing optimized points in terms of probability and the growth or decay of slopes. These studies can potentially demonstrate the optimized potential of these nanoparticles for a variety of applications including energy storage, catalysis, sensing, etc.

关键词： Mixed metal oxides bimetallic oxides optimization probability distribution function Grow-Decay model

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Stochastic modelling of relative water permeability in vegetative soils with implications on stability of bioengineered slope

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STOCHASTIC ENVIRONMENTAL RESEARCH AND RISK ASSESSMENT 2018年第12期32卷 3541-3559页

作者： Singh, Shivam Raj Prakash, Atma Hazra, Budhaditya Sarmah, Ajit Garg, Ankit Zhu, Hong-Hu Indian Inst Technol Guwahati Dept Civil Engn Gauhati 781039 Assam India Univ Auckland Dept Civil & Environm Engn Auckland New Zealand Shantou Univ Dept Civil & Environm Engn Shantou Peoples R China Nanjing Univ Sch Earth Sci & Engn Nanjing Jiangsu Peoples R China

Vegetation is known to influence the hydrological state variables, suction (psi) and volumetric water content (theta(w)) of soil. In addition, vegetation induces heterogeneity in the soil porous structure and consequently the relative permeability (k(r)) of water under unsaturated conditions. The indirect method of utilising the soil water characteristic curve (SWCC) is commonly adopted for the determination of k(r). In such cases, it is essential to address the stochastic behaviour of SWCC, in order to conduct a robust analysis on the k(r) of vegetative cover. The main aim of this study is to address the uncertainties associated with k(r), using probabilistic analysis, for vegetative covers (i.e., grass and tree species) with bare cover as control treatment. We propose two approaches to accomplish the aforesaid objective. The univariate suction approach predicts the probability distribution functions of k(r), on the basis of identified best probability distribution of suction. The bivariate suction and water content approach deals with the bivariate modelling of the water content and suction (SWCC), in order to capture the randomness in the permeability curves, due to presence of vegetation. For this purpose, the dependence structure of psi and theta(w) is established via copula theory, and the k(r) curves are predicted with respect to varying levels of psi theta(w) correlation. The results showed that the k(r) of vegetative covers is substantially lower than that in bare covers. The reduction in k(r) with drying is more in tree cover than grassed cover, since tree roots induce higher levels of suction. Moreover, the air entry value of the soil depends on the magnitude of psi theta(w) correlation, which in turn, is influenced by the type of vegetation in the soil. k(r) is found to be highly uncertain in the desaturation zone of the relative permeability curve. The stochastic behaviour of k(r) is found to be most significant in tree covers. Finally, a simplified cas

关键词： Vegetative cover Suction Copula probability distribution function Soil water characteristic curve (SWCC) Relative permeability

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