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Article
Publication date: 1 July 1996

Z. Chen

Discusses the recent research interest in the relationship between cybernetics and creativity. Uses Brownian motion to review the metaphorical value of cybernetics. Points…

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323

Abstract

Discusses the recent research interest in the relationship between cybernetics and creativity. Uses Brownian motion to review the metaphorical value of cybernetics. Points out that, although an examination from the cybernetics perspective is largely retrospective in nature, the lessons learned from this examination may provide interesting hindsight to guide our future creative activities.

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Kybernetes, vol. 25 no. 5
Type: Research Article
ISSN: 0368-492X

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Book part
Publication date: 10 December 2018

George Levy

Abstract

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Energy Power Risk
Type: Book
ISBN: 978-1-78743-527-8

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Article
Publication date: 3 May 2016

Calum G. Turvey and Paitoon Wongsasutthikul

The purpose of this paper is to argue that a stationary-differenced autoregressive (AR) process with lag greater than 1, AR(q > 1), has certain properties that are…

Abstract

Purpose

The purpose of this paper is to argue that a stationary-differenced autoregressive (AR) process with lag greater than 1, AR(q > 1), has certain properties that are consistent with a fractional Brownian motion (fBm). What the authors are interested in is the investigation of approaches to identifying the existence of persistent memory of one form or another for the purposes of simulating commodity (and other asset) prices. The authors show in theory, and with application to agricultural commodity prices the relationship between AR(q) and quasi-fBm.

Design/methodology/approach

In this paper the authors develop mathematical relationships in support of using AR(q > 1) processes for simulating quasi-fBm.

Findings

From theory the authors show that any AR(q) process is a stationary, self-similar process, with a lag structure that captures the essential elements of scaling and a fractional power law. The authors illustrate through various means the approach, and apply the quasi-fractional AR(q) process to agricultural commodity prices.

Research limitations/implications

While the results can be applied to most time series of commodity prices, the authors limit the evaluation to the Gaussian case. Thus the approach does not apply to infinite-variance models.

Practical implications

The approach to using the structure of an AR(q > 1) model to simulate quasi-fBm is a simple approach that can be applied with ease using conventional Monte Carlo methods.

Originality/value

The authors believe that the approach to simulating quasi-fBm using standard AR(q > 1) models is original. The approach is intuitive and can be applied easily.

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Agricultural Finance Review, vol. 76 no. 1
Type: Research Article
ISSN: 0002-1466

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Article
Publication date: 17 August 2010

Imene Safer Chakroun and Abdelkader Hamdouni

The purpose of this paper is to discuss a widespread idea in the financial literature: information in financial markets is free. Indeed, whenever an investor wants to…

Abstract

Purpose

The purpose of this paper is to discuss a widespread idea in the financial literature: information in financial markets is free. Indeed, whenever an investor wants to intervene to purchase and/or to sell, he/she faces the need to access the information, which he/she judges to ensure an optimal decision.

Design/methodology/approach

The paper uses the entropy statistics in order to estimate the information cost of the assets of the Tunisian stock market over the period extending from 2002 to 2005.

Findings

The obtained results show that the information costs follow a Brownian motion. This finding lends empirical support to the theoretical position that has always been adopted in the relevant literature: in finance, as in economy, the majority of the series follow a Brownian motion.

Practical implications

The proposed methodology offers investors the opportunity to estimate the information cost by taking into account the quotation probability, a simple approach that can be used not only by fund managers, but also by financial market investors.

Originality/value

The paper uses entropy as a relatively new tool applied in financial theory. It offers a new understanding of information cost. The paper will be of interest for financial market investors and academics.

Details

The Journal of Risk Finance, vol. 11 no. 4
Type: Research Article
ISSN: 1526-5943

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Article
Publication date: 26 August 2014

Ali J. Chamkha, M. Rashad and Rama Subba Reddy Gorla

The purpose of this paper is to present a boundary layer analysis for the mixed convection past a vertical wedge in a porous medium saturated with a power law type…

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Abstract

Purpose

The purpose of this paper is to present a boundary layer analysis for the mixed convection past a vertical wedge in a porous medium saturated with a power law type non-Newtonian nanofluid. Numerical results for friction factor, surface heat transfer rate and mass transfer rate have been presented for parametric variations of the buoyancy ratio parameter Nr, Brownian motion parameter Nb, thermophoresis parameter Nt, Lewis number Le and the power law exponent n. The dependency of the friction factor, surface heat transfer rate (Nusselt number) and mass transfer rate on these parameters has been discussed.

Design/methodology/approach

This general non-linear problem cannot be solved in closed form and, therefore, a numerical solution is necessary to describe the physics of the problem. An implicit, tri-diagonal finite-difference method has proven to be adequate and sufficiently accurate for the solution of this kind of problems. Therefore, it is adopted in the present study. Variable step sizes were used. The convergence criterion employed in this study is based on the difference between the current and the previous iterations. When this difference reached 10−5 for all the points in the η directions, the solution was assumed to be converged, and the iteration process was terminated.

Findings

The results indicate that as the buoyancy ratio parameter (Nr) and thermophoresis parameter (Nt) increase, the friction factor increases whereas the heat transfer rate (Nusselt number) and mass transfer rate (Sherwood number) decrease. As the Brownian motion parameter (Nb) increases, the friction factor and surface mass transfer rates increase whereas the surface heat transfer rate decreases. As Le increases, mass transfer rates increase. As the power law exponent n increases, the heat and mass transfer rates increase.

Research limitations/implications

The analysis is valid for natural convection dominated regime. The combined forced and natural convection dominated regimes will be reported in a future work.

Practical implications

The approach used is useful in optimizing the porous media heat transfer problems in geothermal energy recovery, crude oil extraction, ground water pollution, thermal energy storage and flow through filtering media.

Originality/value

The results of the study may be of some interest to the researchers of the field of porous media heat transfer. Porous foam and microchannel heat sinks used for electronic cooling are optimized utilizing the porous medium. The utilization of nanofluids for cooling of microchannel heat sinks requires understanding of fundamentals of nanofluid convection in porous media.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 24 no. 7
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 1 August 2016

Feng-Rung Hu and Jia-Sheng Hu

– The purpose of this paper is to present a proportional-integral (PI) observer design on a linear system with stochastic noises.

Abstract

Purpose

The purpose of this paper is to present a proportional-integral (PI) observer design on a linear system with stochastic noises.

Design/methodology/approach

The noised disturbances are modeled as independent Brownian motions for various affections, such as radiation, heat, and material fatigue. These phenomena are common in applications, such as biomolecules, nonlinear control, and biochemical networks. Under this framework, this paper proposes a new approach on a PI observer in terms of four crucial theorems, and an illustrative numerical example is given to verify the proposed design.

Findings

The results provide potential solutions for system fault tolerance and isolation.

Originality/value

This paper proposes a design, solvability, and controllability analysis on a PI observer in terms of four crucial theorems.

Details

Engineering Computations, vol. 33 no. 6
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 23 September 2021

Yu Bai, Huiling Fang and Yan Zhang

This paper aims to present the effect of entropy generation on the unsteady flow of upper-convected Maxwell nanofluid past a wedge embedded in a porous medium in view of…

Abstract

Purpose

This paper aims to present the effect of entropy generation on the unsteady flow of upper-convected Maxwell nanofluid past a wedge embedded in a porous medium in view of buoyancy force. Cattaneo-Christov double diffusion theory simulates the processes of energy phenomenon and mass transfer. Meanwhile, Brownian motion, thermophoresis and convective boundary conditions are discussed to further visualize the heat and mass transfer properties.

Design/methodology/approach

Coupled ordinary differential equations are gained by appropriate similar transformations and these equations are manipulated by the Homotopy analysis method.

Findings

The result is viewed that velocity distribution is a diminishing function with boosting the value of unsteadiness parameter. Moreover, fluid friction irreversibility is dominant as the enlargement in Brinkman number. Then controlling the temperature and concentration difference parameters can effectively regulate entropy generation.

Originality/value

This paper aims to address the effect of entropy generation on unsteady flow, heat and mass transfer of upper-convected Maxwell nanofluid over a stretched wedge with Cattaneo-Christov double diffusion, which provides a theoretical basis for manufacturing production.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 5 July 2021

Alireza Shariatifard, Dariuosh Kamali, Saeid Hejri and Emad Hasani Malekshah

This study aims to employ a modern numerical approach for conducting the simulations, which uses the smoothed-profile lattice Boltzmann method. Two separate distribution…

Abstract

Purpose

This study aims to employ a modern numerical approach for conducting the simulations, which uses the smoothed-profile lattice Boltzmann method. Two separate distribution functions for flow and temperature fields are used to solve the Navier–Stokes equations in the most efficient manner. In addition, the Koo–Kleinstreuer–Li model is used to calculate the dynamic viscosity and thermal conductivity in the desired volume fractions, and the effect of Brownian motion is taken into consideration.

Design/methodology/approach

Nowadays, because of enhanced global price of oil and critical issue of global warming, a significant demand for using renewable energy exists. The solar energy is one of the most popular forms of renewable energy. The solar collector can be used to collect and trap the energy received from the sun. The present work focuses on introducing and investigating a parabolic-trough solar collector.

Findings

To analyze all hydrodynamic and thermal views of the solar collector, the structure of nanofluid stream, distribution of temperature, local dissipations because of flow and heat transfer, volumetric entropy production, Bejan number vs Rayleigh number and volume fraction are presented. Also, three different configurations for profile of solar receiver are designed and studied.

Originality/value

The originality of the present work is in using a modern numerical approach for a well-known application. Also, the effect of Brownian motion is taken into account which significantly enhances the accuracy.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 22 March 2021

Z.B. Xing, Xingchao Han, Hanbing Ke, Q.G. Zhang, Zhiping Zhang, Huijin Xu and Fuqiang Wang

A combination of highly conductive porous media and nanofluids is an efficient way for improving thermal performance of relevant applications. For precisely predicting the…

Abstract

Purpose

A combination of highly conductive porous media and nanofluids is an efficient way for improving thermal performance of relevant applications. For precisely predicting the flow and thermal transport of nanofluids in porous media, the purpose of this paper is to explore the inter-phase coupling numerical methods.

Design/methodology/approach

Based on the lattice Boltzmann (LB) method, this study combines the convective flow, non-equilibrium thermal transport and phase interactions of nanofluids in porous matrix and proposes a new multi-phase LB model. The micro-scale momentum and heat interactions are especially analyzed for nanoparticles, base fluid and solid matrix. A set of three-phase LB equations for the flow/thermal coupling of base fluid, nanoparticles and solid matrix is established.

Findings

Distributions of nanoparticles, velocities for nanoparticles and the base fluid, temperatures for three phases and interaction forces are analyzed in detail. Influences of parameters on the nanofluid convection in the porous matrix are examined. Thermal resistance of nanofluid convective transport in porous structures are comprehensively discussed with the models of multi-phases. Results show that the Rayleigh number and the Darcy number have significant influences on the convective characteristics. The result with the three-phase model is mildly larger than that with the local thermal non-equilibrium model.

Originality/value

This paper first creates the multi-phase theoretical model for the complex coupling process of nanofluids in porous structures, which is useful for researchers and technicians in fields of thermal science and computational fluid dynamics.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 31 no. 8
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 1 July 2020

Ankita Bisht and Rajesh Sharma

The main purpose of this study is to present a non-similar analysis of two-dimensional boundary layer flow of non-Newtonian nanofluid over a vertical stretching sheet with…

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82

Abstract

Purpose

The main purpose of this study is to present a non-similar analysis of two-dimensional boundary layer flow of non-Newtonian nanofluid over a vertical stretching sheet with variable thermal conductivity. The Sisko fluid model is used for non-Newtonian fluid with an exponent (n* > 1), that is, shear thickening fluid. Buongiorno model for nanofluid accounting Brownian diffusion and thermophoresis effects is used to model the governing differential equations.

Design/methodology/approach

The governing boundary layer equations are converted into nondimensional coupled nonlinear partial differential equations using appropriate transformations. The resultant differential equations are solved numerically using implicit finite difference scheme in association with the quasilinearization technique.

Findings

This analysis shows that the temperature raises for thermal conductivity parameter and velocity ratio parameter while decreases for the thermal buoyancy parameter. The thermophoresis and Brownian diffusion parameter that characterizes the nanofluid flow enhances the temperature and reduces the heat transfer rate. Skin friction drag can be effectively reduced by proper control of the values of thermal buoyancy and velocity ratio parameter.

Practical implications

The wall heating and cooling investigation result in the analysis of the control parameters that are related to the designing and manufacturing of thermal systems for cooling applications and energy harvesting. These control parameters have practical significance in the designing of heat exchangers and solar thermal collectors, in glass and polymer industries, in the extrusion of plastic sheets, the process of cooling of the metallic plate, etc.

Originality/value

To the best of authors’ knowledge, it is found from the literature survey that no similar work has been published which investigates the non-similar solution of Sisko nanofluid with variable thermal conductivity using finite difference method and quasilinearization technique.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 31 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

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