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Article
Publication date: 21 May 2013

P. Tománek, P. Škarvada, D. Dallaeva, L. Grmela, R. Macků and S. Smith

Monocrystalline silicon is still very interesting material for solar cells fabrication due to its quality and external efficiency. Nevertheless during a tailoring of eligible…

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Abstract

Monocrystalline silicon is still very interesting material for solar cells fabrication due to its quality and external efficiency. Nevertheless during a tailoring of eligible silicon wafers, some inhomogeneities or irregularities emerge and provide defects which give trouble to good operation of solar panels. Generally, there are two classes of defects in silicon wafer: material defects due to imperfections or irregularity in crystal structure (point, line, square or volume defects), and defects induced by wafer processing. To avoid a use of damaged cells, macroscopic and microscopic measurement techniques must be applied. In this paper we present a microscopic method combining electrical noise measurements with scanning probe localization of luminous micro-spots defects. The paper brings experimental results showing local electric and optical investigations of defects in etched monocrystalline silicon solar cells and a use of cold field emission tungsten electrode as a local probe for apertureless scanning near-field optical microscope.

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Article
Publication date: 12 April 2013

Chunlei Ruan, Jie Ouyang and Hongping Zhang

The purpose of this paper is to examine the macroscopic and microscopic fields of fiber suspensions in the non‐isothermal situations, also to examine the effect of fiber on this…

116

Abstract

Purpose

The purpose of this paper is to examine the macroscopic and microscopic fields of fiber suspensions in the non‐isothermal situations, also to examine the effect of fiber on this non‐isothermal system.

Design/methodology/approach

Control equations are coupled and simultaneously solved by collocated finite volume method on fully triangular meshes.

Findings

Temperature dependence and wall temperature have significant effect on both macroscopic and microscopic fields of fiber suspensions. Moreover, the influence of fiber on the non‐isothermal system is similar to that of the isothermal system.

Originality/value

This is the first time that the microstructures of both molecules and fibers are presented in the non‐isothermal condition and it is hoped that the results will provide more insight into the microscopics of complex flows.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 23 no. 3
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 14 March 2019

Ali Daher, Amine Ammar and Abbas Hijazi

The purpose of this paper is to develop a numerical model for the simulation of the dynamics of nanoparticles (NPs) at liquid–liquid interfaces. Two cases have been studied, NPs…

148

Abstract

Purpose

The purpose of this paper is to develop a numerical model for the simulation of the dynamics of nanoparticles (NPs) at liquid–liquid interfaces. Two cases have been studied, NPs smaller than the interfacial thickness, and NPs greater than the interfacial thickness.

Design/methodology/approach

The model is based on the molecular dynamics (MD) simulation in addition to phase field (PF) method, through which the discrete model of particles motion is superimposed on the continuum model of fluids which is a new ide a in numerical modeling. The liquid–liquid interface is modeled using the diffuse interface model.

Findings

For NPs smaller than the interfacial thickness, the results obtained show that the concentration gradient of one fluid in the other gives rise to a hydrodynamic drag force that drives the NPs to agglomerate at the interface. Whereas, for spherical NPs greater than the interfacial thickness, the results show that such NPs oscillate at the interface which agrees with some experimental studies.

Practical implications

The results are important in the field of numerical modeling, especially that the model is general and can be used to study different systems. This will be of great interest in the field of studying the behavior of NPs inside fluids and near interfaces, which enters in many industrial applications.

Originality/value

The idea of superimposing the molecular dynamic method on the PF method is a new idea in numerical modeling.

Details

Engineering Computations, vol. 36 no. 3
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 7 March 2016

Adriano Sciacovelli and Vittorio Verda

The purpose of this paper is to investigate efficient designs of a shell-and-tube latent thermal energy storage system through an approach based on the analysis of entropy…

351

Abstract

Purpose

The purpose of this paper is to investigate efficient designs of a shell-and-tube latent thermal energy storage system through an approach based on the analysis of entropy generation. It proposes innovative branched fins to maximize the performance of the system.

Design/methodology/approach

A computational fluid dynamic (CFD) model is first used to detail the thermo-fluid dynamic transient behavior of the latent heat storage system. The model account for phase change, buoyancy driven fluid flow and heat transfer during the process of energy retrieval from the storage unit (solidification). The CFD model is then used to evaluate locally the entropy generation rate during the process. On the basis of the insight gathered through the analysis of the entropy generation, the design of the fins is gradually modified aiming at the maximization of the performance of the storage system.

Findings

The best fins design leads to a twofold increase of the solidification rate in the latent heat storage unit. The corresponding second-law efficiency shows an increase of 13 percent compared with traditional fins.

Research limitations/implications

The analysis is based on a single tube configuration of the storage system which implies that non-homogeneous effects due to multiple tubes are not considered. Nevertheless, the proposed design procedure is general and could be applied to different configurations of latent heat thermal storage systems.

Practical implications

Entropy generation analysis provides a very useful design approach to develop configurations of latent heat storage systems that may overcome current performance limitations. Also, practitioners in the field may also benefit of the results for improving current installations of energy storage systems.

Originality/value

Entropy generation is adapted and used to find an optimal design for a time dependent process. That is, a geometrical configuration is found for maximizing the performance over a span of time. This is a key aspect of the work because there is a strong trend toward energy systems operating under transient conditions.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 26 no. 2
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 7 September 2023

Esra Kandemir Beser

The purpose of this study is to create an extended equivalent circuit model for a compound DC motor, consisting completely of electrical parameters and quantities.

157

Abstract

Purpose

The purpose of this study is to create an extended equivalent circuit model for a compound DC motor, consisting completely of electrical parameters and quantities.

Design/methodology/approach

The dynamic model of the compound DC motor is obtained by establishing the voltage equations for the armature and excitation circuit and the mechanical equation for the mechanical part. The mechanical parameters in the dynamic model are converted into electrical parameters with an electrical circuit proposed for the mechanical part. By combining the armature and excitation circuits with the electrical circuit created for the mechanical part, the extended equivalent circuit model of the compound DC motor is obtained. Because the proposed extended equivalent model is completely an electrical circuit, simulations can be made in the circuit simulation programme. Simulations of the proposed compound DC motor circuit were carried out, and the accuracy of the proposed circuit was verified by performing experimental studies with an existing compound motor.

Findings

When comparing speed and current profiles in experiments and simulations, it is seen that compound DC motor can be modelled with the proposed equivalent circuit including completely electrical elements in a simulation programme for the circuits. The results show that the proposed equivalent circuit satisfies the dynamic model of the compound motor.

Originality/value

In DC machine models, armature and excitation circuits are given as an electrical circuit, and mechanical part of the machine is modelled by only mechanical equations. The originality of this study is converting the dynamic model of an electrical machine consisting of electrical and mechanical equations into a completely electrical circuit. With the proposed method, the dynamic model of many motors can be converted into a completely electrical circuit. In this way, motors can be simulated as an electrical circuit in simulation programmes for the circuits, and the dynamic behaviour of motors can be obtained.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 42 no. 6
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 22 September 2023

Aying Zhang, Ziyu Xing and Haibao Lu

The purpose of this paper is to study the mechanochemical effect and self-growth mechanism of double-network (DN) gel and to provide a quasiperiodic model for rubber elasticity.

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Abstract

Purpose

The purpose of this paper is to study the mechanochemical effect and self-growth mechanism of double-network (DN) gel and to provide a quasiperiodic model for rubber elasticity.

Design/methodology/approach

The chemical reaction kinetics is used to identify the mechanochemical transition probability of host brittle network and to explore the mechanical behavior of endosymbiont ductile network. A quasiperiodic model is proposed to characterize the cooperative coupling of host–endosymbiont networks using the Penrose tiling of a 2 × 2 matrix. Moreover, a free-energy model is formulated to explore the constitutive stress–strain relationship for the DN gel based on the rubber elasticity theory and Gent model.

Findings

In this study, a quasiperiodic graph model has been developed to describe the cooperative interaction between brittle and ductile networks, which undergo the mechanochemical coupling and mechanical stretching behaviors, respectively. The quasiperiodic Penrose tiling determines the mechanochemistry and self-growth effect of DNs.

Originality/value

It is expected to formulate a quasiperiodic graph model of host–guest interaction between two networks to explore the working principle of mechanical and self-growing behavior in DN hydrogels, undergoing complex mechanochemical effect. The effectiveness of the proposed model is verified using both finite element analysis and experimental results of DN gels reported in literature.

Details

Pigment & Resin Technology, vol. 53 no. 6
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 29 September 2023

Jarett D. Haley, Amber N. Williams, Rosemary J. Perez and Claire K. Robbins

The purpose of this study is to explore how US graduate students described their diversity, equity and inclusion (DEI) education and engagement experiences outside their academic…

467

Abstract

Purpose

The purpose of this study is to explore how US graduate students described their diversity, equity and inclusion (DEI) education and engagement experiences outside their academic departments.

Design/methodology/approach

This study used a critical constructivist qualitative approach and methods (i.e. interviews) to explore how 44 graduate students across various disciplines and fields at two public research institutions in the USA described their DEI education and engagement experiences outside their departments.

Findings

Students identified expanded DEI and professional knowledge as key learning outcomes, while also highlighting the benefits and negative effects of the identity-centered (dis)connection, community and personal fulfillment that came from these experiences.

Research limitations/implications

Given that DEI education and engagement opportunities addressed some students’ needs and were unsatisfactory for others, more scholarship on the nature of these experiences is needed to better understand factors that contribute to students’ desirable and undesirable outcomes. There are also practical implications for faculty who advise graduate students and administrators who are responsible for funding the campus spaces in which these experiences occurred (e.g. graduate colleges, identity-based student organizations).

Originality/value

Few studies have explored graduate students’ participation in DEI education and engagement opportunities outside of their academic departments. Consequently, the efficacy of these initiatives, and the extent to which students benefit from them, warrant investigation. This study, thus, adds to researchers’ and practitioners’ understanding of this topic by highlighting the benefits and limitations of these experiences for graduate students.

Details

Studies in Graduate and Postdoctoral Education, vol. 15 no. 1
Type: Research Article
ISSN: 2398-4686

Keywords

Available. Open Access. Open Access
Article
Publication date: 9 July 2021

Jan Pringle, Ruth Jepson, Alison Dawson, Louise McCabe and Alison Bowes

One limitation of research that assesses the effectiveness of physical activity interventions for people with dementia is that most do not describe the intervention in sufficient…

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Abstract

Purpose

One limitation of research that assesses the effectiveness of physical activity interventions for people with dementia is that most do not describe the intervention in sufficient detail to ascertain a theoretical basis or mechanism of action that determines the effective components. This paper aims to identify studies which evaluate the mechanisms of action of physical activity interventions for people with dementia, to further inform effective intervention development.

Design/methodology/approach

Papers were screened for evidence of evaluation of specific forms of physical activity, using pre-defined inclusion criteria. Analysis was conducted to ascertain if mechanisms of action were corroborated by data within and between studies.

Findings

The authors identified 26 studies with a measured mechanism of action; these related to the effects of physical activity on either neurological structure or endocrinal markers, including hormones. Physical activity had potential to reduce hippocampal atrophy, increase neural recruitment, activate the noradrenergic system and improve anti-inflammatory responses. While individual studies were hampered by small sample sizes, the body of evidence indicated that physical activity may have potential to delay cognitive decline.

Practical implications

Mechanisms of action in relation to dementia and physical activity are likely to be multifaceted, and physical activity may be protective against progression in the early stages of cognitive decline. Physical activity may be of greatest benefit if incorporated into on-going lifestyle, rather than engaged in for short periods, and combined with social interaction.

Originality/value

This paper is unique in its focus on the mechanisms of action of physical activity interventions for people with dementia.

Details

Quality in Ageing and Older Adults, vol. 22 no. 1
Type: Research Article
ISSN: 1471-7794

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Article
Publication date: 31 October 2023

M. Candace Christensen, María Verónica Elías, Érica Alcocer and Shannyn Vicente

This study aims to illustrate how white supremacy culture can be produced within nonprofit organizations with a mandate to serve marginalized communities and provide practical…

219

Abstract

Purpose

This study aims to illustrate how white supremacy culture can be produced within nonprofit organizations with a mandate to serve marginalized communities and provide practical suggestions for preventing oppression.

Design/methodology/approach

The site of inquiry was a nonprofit organization in south central Texas that provides social support to queer and trans youth. Through critical ethnography, the researchers evaluated the organization's processes and structure (including hierarchy, decision-making, fundraising and interactions between leaders, partners and affected groups) to explore how the organization perpetuated attributes of white supremacy culture.

Findings

Data reveal that the organization alienates the youth, volunteers and employees through defensiveness, fear of open conflict, paternalism, perfectionism and power-hoarding.

Originality/value

A dearth of research focuses on how white supremacy culture manifests in organizations serving marginalized communities. This paper addresses this gap by focusing on a nonprofit organization in central Texas that supports queer and trans youth. The authors offer recommendations for addressing white supremacy culture in organizations and suggest future research opportunities.

Details

Qualitative Research in Organizations and Management: An International Journal, vol. 18 no. 4
Type: Research Article
ISSN: 1746-5648

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Article
Publication date: 28 November 2023

John H. Bickford

This content analysis examines the historical representation of Margaret Sanger within trade books. From the framework of the historiography, this paper unpacks how common…

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Abstract

Purpose

This content analysis examines the historical representation of Margaret Sanger within trade books. From the framework of the historiography, this paper unpacks how common curricular resources depict an American icon with a complicated past.

Design/methodology/approach

In this paper, the author conducted a content analysis of biographies and expository compilations featuring Sanger. The entire data pool were sampled and analyzed.

Findings

The trade books, particularly the biographies, historically represented Sanger in most categories. Sanger's international direct action and eugenics were two misrepresented areas. Expository compilations, with more limited space than biographies, contained more omissions and minimized or vague depictions of key areas. Findings did not appear dependent upon date of publication.

Originality/value

This study explores an icon of America's free speech battles and birth control rights at a time when culture wars are shaping current events. No researchers have previously explored Sanger's historical representation within trade books.

Details

Social Studies Research and Practice, vol. 19 no. 3
Type: Research Article
ISSN: 1933-5415

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