D.P. Zielinski and V.R. Voller
The purpose of this paper is to develop an alternative numerical approach for describing fractional diffusion in Cartesian and non‐Cartesian domains using a Monte Carlo random…
Abstract
Purpose
The purpose of this paper is to develop an alternative numerical approach for describing fractional diffusion in Cartesian and non‐Cartesian domains using a Monte Carlo random walk scheme. The resulting domain shifting scheme provides a numerical solution for multi‐dimensional steady state, source free diffusion problems with fluxes expressed in terms of Caputo fractional derivatives. This class of problems takes account of non‐locality in transport, expressed through parameters representing both the extent and direction of the non‐locality.
Design/methodology/approach
The method described here follows a similar approach to random walk methods previously developed for normal (local) diffusion. The key differences from standard methods are: first, the random shifting of the domain about the point of interest with, second, shift steps selected from non‐symmetric, power‐law tailed, Lévy probability distribution functions.
Findings
The domain shifting scheme is verified by comparing predictive solutions to known one‐dimensional and two‐dimensional analytical solutions for fractional diffusion problems. The scheme is also applied to a problem of fractional diffusion in a non‐Cartesian annulus domain. In contrast to the axisymmetric, steady state solution for normal diffusion, a non‐axisymmetric solution results.
Originality/value
This is the first random walk scheme to utilize the concept of allowing the domain to undergo the random walk about a point of interest. Domain shifting scheme solutions of fractional diffusion in non‐Cartesian domains provide an invaluable tool to direct the development of more sophisticated grid based finite element inspired fractional diffusion schemes.
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Zhu Fanglong, Feng Qianqian, Liu Rangtong, Li Kejing and Zhou Yu
– The purpose of this paper is to employ a fractional approach to predict the permeability of nonwoven fabrics by simulating diffusion process.
Abstract
Purpose
The purpose of this paper is to employ a fractional approach to predict the permeability of nonwoven fabrics by simulating diffusion process.
Design/methodology/approach
The method described here follows a similar approach to anomalous diffusion process. The relationship between viscous hydraulic permeability and electrical conductivity of porous material is applied in the derivation of fractional power law of permeability.
Findings
The presented power law predicted by fractional method is validated by the results obtained from simulation of fluid flow around a 3D nonwoven porous material by using the lattice-Boltzmann approach. A relation between the fluid permeability and the fluid content (filling fraction), namely, following the power law of the form, was derived via a scaling argument. The exponent n is predominantly a function of pore-size distribution dimension and random walk dimension of the fluid.
Originality/value
The fractional scheme by simulating diffusion process presented in this paper is a new method to predict wicking fluid flow through nonwoven fabrics. The forecast approach can be applied to the prediction of the permeability of other porous materials.
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Hong-Yan Liu, Ji-Huan He and Zheng-Biao Li
Academic and industrial researches on nanoscale flows and heat transfers are an area of increasing global interest, where fascinating phenomena are always observed, e.g. admirable…
Abstract
Purpose
Academic and industrial researches on nanoscale flows and heat transfers are an area of increasing global interest, where fascinating phenomena are always observed, e.g. admirable water or air permeation and remarkable thermal conductivity. The purpose of this paper is to reveal the phenomena by the fractional calculus.
Design/methodology/approach
This paper begins with the continuum assumption in conventional theories, and then the fractional Gauss’ divergence theorems are used to derive fractional differential equations in fractal media. Fractional derivatives are introduced heuristically by the variational iteration method, and fractal derivatives are explained geometrically. Some effective analytical approaches to fractional differential equations, e.g. the variational iteration method, the homotopy perturbation method and the fractional complex transform, are outlined and the main solution processes are given.
Findings
Heat conduction in silk cocoon and ground water flow are modeled by the local fractional calculus, the solutions can explain well experimental observations.
Originality/value
Particular attention is paid throughout the paper to giving an intuitive grasp for fractional calculus. Most cited references are within last five years, catching the most frontier of the research. Some ideas on this review paper are first appeared.
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Cynthia Mejia and Edwin N. Torres
Asynchronous video interviews (AVIs) enable recruiters and job candidates to conduct and review employment interviews at different points in time, promising improved cost and time…
Abstract
Purpose
Asynchronous video interviews (AVIs) enable recruiters and job candidates to conduct and review employment interviews at different points in time, promising improved cost and time efficiencies for all users. This research aims to investigate the implementation and normalization process of AVI in the hospitality industry with the unified theory of acceptance and use of technology (UTAUT) and the normalization process theory (NPT) providing theoretical support.
Design/methodology/approach
Semi-structured interviews have been conducted with hiring managers from three different hospitality companies, which were in different stages of the implementation process. The data have been recorded, transcribed and coded according to the UTAUT and NPT constructs, revealing emergent themes.
Findings
Five overarching themes emerged: AVI effort and efficiency expectation; augmentation to the interview process; challenges for the applicant; challenges for the recruiter; and issues with applicant interviewing aesthetics. Additional coding and analysis with NPT identified the following in terms of evaluation of the implementation process: participants’ implementation activities showed a tendency to emanate from cognitive participation (relationship work), leading to coherence (sense-making work), followed by collective action (enactment of work/operational work) and finally reflexive monitoring (appraisal work).
Practical implications
Findings from this research include recommendations for the best practices integrating AVI into the hospitality employee selection process.
Originality/value
Given the increased demands on the recruitment and selection of talent in the hospitality industry, several organizations have turned to mechanized HR software platforms. The impact of interview modalities and particularly AVI has received limited research attention, thus this study expanded this new stream of literature. Furthermore, this research is among a nascent stream using NPT to evaluate the implementation and normalization of this new technology.
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Mariusz Deja and Dawid Zielinski
The purpose of this study is to evaluate the geometric quality of small diameter holes in parts printed by direct metal laser sintering (DMLS) technology. An in-process optical…
Abstract
Purpose
The purpose of this study is to evaluate the geometric quality of small diameter holes in parts printed by direct metal laser sintering (DMLS) technology. An in-process optical inspection method is proposed and assessed during a pilot study. The influence of the theoretical hole diameter assumed in a computer-aided design (CAD) system and the sample thickness (hole length) on the hole clearance was analyzed.
Design/methodology/approach
The samples are made of two different materials: EOS MaragingSteel MS1 and aluminium alloy EOS Aluminium consisted of straight through holes of different diameters and lengths. Dimensional and shape accuracy of the holes were determined with the use of the image processing software and the computer analysis of two-dimensional (2-D) images. The definition of the equivalent hole diameter was proposed to calculate the hole clearance. Feret’s diameters were determined for the evaluation of the shape accuracy.
Findings
The dependency between the equivalent hole diameter and the theoretical diameter was approximated by the linear function for a specific sample thickness. Additionally, a general empirical model for determining the hole clearance was developed, allowing for calculating the equivalent hole diameter as a function of a sample thickness and a theoretical hole diameter.
Practical implications
Developed functions can be used by designers for a proper assignment of a hole diameter to achieve the required patency. The relevant procedures and macros based on proposed empirical models can be embedded in CAD systems to support the designing process.
Originality/value
The analysis of the geometric quality of the holes in parts printed by DMLS was based on the computer analysis of 2-D images. The proposed method of assessing the shape accuracy of straight through holes is relatively cheap, is widely available and can be applied to the features of other shapes produced by three-dimensional printing.
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There are two stages in equation solving. These are localization of solutions and their refinement. Many methods ignore problems concerning localization. Generality of methods…
Abstract
There are two stages in equation solving. These are localization of solutions and their refinement. Many methods ignore problems concerning localization. Generality of methods falls quickly with growth of system complexity. Then a random search guided by heuristics may be some cure to complex system solving. An algorithm is proposed here in the form of Turbo Pascal program. It is composed of three methods. The program user controls system solving in function of system complexity.
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S. Thomas Ng, Daisy X.M. Zheng and Jessie Z. Xie
Construction resources are often limited, and there is a need to ensure resources are carefully allocated to avoid resource wastage and/or project delay. While mathematical and…
Abstract
Purpose
Construction resources are often limited, and there is a need to ensure resources are carefully allocated to avoid resource wastage and/or project delay. While mathematical and heuristic models were developed to resolve the conflicts between activities, none of them has been proven to be totally satisfactory. The aim of this paper is to explore this.
Design/methodology/approach
In this paper, a novel heuristic method known as a pull‐driven approach (PDA) is proposed; and this approach encourages a lean consideration of resource supply and partnering between activities. Two case studies are presented to illustrate how PDA can be applied. A comparison with another heuristic approach, namely the ranked positional weight method is conducted to illustrate the efficiency of the proposed approach.
Findings
Using the PDA approach, all the activities strive to find matching partners to pull resources to their sides. The resources are, therefore, no longer passively pushed to a single activity with high ranking but a combination of activities that can demonstrate their superiority in resource utilisation will actively win the necessary resources.
Originality/value
This approach has an ability to deal with intermittent activities and locate the lean (no‐waste) supply level of each resource.
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Aimad Koulali, Paweł Ziółkowski, Piotr Radomski, Luciano De Sio, Jacek Zieliński, María Cristina Nevárez Martínez and Dariusz Mikielewicz
In the wake of the COVID-19 pandemics, the demand for innovative and effective methods of bacterial inactivation has become a critical area of research, providing the impetus for…
Abstract
Purpose
In the wake of the COVID-19 pandemics, the demand for innovative and effective methods of bacterial inactivation has become a critical area of research, providing the impetus for this study. The purpose of this research is to analyze the AuNPs-mediated photothermal inactivation of E. coli. Gold nanoparticles irradiated by laser represent a promising technique for combating bacterial infection that combines high-tech and scientific progress. The intermediate aim of the work was to present the calibration of the model with respect to the gold nanorods experiment. The purpose of this work is to study the effect of initial concentration of E. coli bacteria, the design of the chamber and the laser power on heat transfer and inactivation of E. coli bacteria.
Design/methodology/approach
Using the CFD simulation, the work combines three main concepts. 1. The conversion of laser light to heat has been described by a combination of three distinctive approximations: a- Discrete particle integration to take into account every nanoparticle within the system, b- Rayleigh-Drude approximation to determine the scattering and extinction coefficients and c- Lambert–Beer–Bourger law to describe the decrease in laser intensity across the AuNPs. 2. The contribution of the presence of E. coli bacteria to the thermal and fluid-dynamic fields in the microdevice was modeled by single-phase approach by determining the effective thermophysical properties of the water-bacteria mixture. 3. An approach based on a temperature threshold attained at which bacteria will be inactivated, has been used to predict bacterial response to temperature increases.
Findings
The comparison of the thermal fields and temporal temperature changes obtained by the CFD simulation with those obtained experimentally confirms the accuracy of the light-heat conversion model derived from the aforementioned approximations. The results show a linear relationship between maximum temperature and variation in laser power over the range studied, which is in line with previous experimental results. It was also found that the temperature inside the microchamber can exceed 55 °C only when a laser power higher than 0.8 W is used, so bacterial inactivation begins.
Research limitations/implications
The experimental data allows to determinate the concentration of nanoparticles. This parameter is introduced into the mathematical model obtaining the same number of AuNPs. However, this assumption introduces a certain simplification, as in the mathematical model the distribution of nanoparticles is uniform.
Practical implications
This work is directly connected to the use of gold nanoparticles for energy conversion, as well as the field of bacterial inactivation in microfluidic systems such as lab-on-a-chip. Presented mathematical and numerical models can be extended to the entire spectrum of wavelengths with particular use of white light in the inactivation of bacteria.
Originality/value
This work represents a significant advancement in the field, as to the best of the authors’ knowledge, it is the first to employ a single-phase computational fluid dynamics (CFD) approach specifically combined with the thermal inactivation of bacteria. Moreover, this research pioneers the use of a numerical simulation to analyze the temperature threshold of photothermal inactivation of E. coli mediated by gold nanorods (AuNRs). The integration of these methodologies offers a new perspective on optimizing bacterial inactivation techniques, making this study a valuable contribution to both computational modeling and biomedical applications.