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Article
Publication date: 25 May 2010

Vahid Afshari and Changiz Dehghanian

The purpose of this paper is to demonstrate the effect of grain‐size reduction on the stability of passive films formed on pure iron. Possible mechanisms capable of their…

622

Abstract

Purpose

The purpose of this paper is to demonstrate the effect of grain‐size reduction on the stability of passive films formed on pure iron. Possible mechanisms capable of their improvement are discussed.

Design/methodology/approach

Nanocrystalline iron was produced by pulse electrodeposition using a citric acid bath. The grain size of the nanocrystalline surface was analyzed by X‐ray diffractometry and atomic force microscopy. The tests were carried out in 95‐97 percent H2SO4 aqueous solution. The stability of the passive films was investigated using Tafel polarization curves and electrochemical impedance spectroscopy measurements.

Findings

The corrosion resistance of Fe in concentrated sulfuric acid solution increased as the grain size decreased from microcrystalline to nanocrystalline. The decreased passive current density of nanocrystalline Fe may be due to the more rapid formation of continuous passive films at surface crystalline defects, compared with coarse‐grained Fe structures.

Originality/value

The behavior of passive film growth and corrosion is considered in terms of excess free energy caused by the nanocrystalline surface.

Details

Anti-Corrosion Methods and Materials, vol. 57 no. 3
Type: Research Article
ISSN: 0003-5599

Keywords

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Article
Publication date: 14 August 2024

Mehrdad Leylabi, Sara Malekan and Mehdi Majidpour

The aim of this paper is to explain that what main characteristics financial technologies should have so that lead to improve the transparency of institutions and whether the…

75

Abstract

Purpose

The aim of this paper is to explain that what main characteristics financial technologies should have so that lead to improve the transparency of institutions and whether the integrated monetary banking system deployed in free-interest institutions has affected the transparency of these institutions in terms of those characteristics or not? In this study, the integrated monetary banking system will be studied subject to implementation of the Shafagh project.

Design/methodology/approach

Based on the literature review and the experts' opinions, the principles of the research questions were explained. Then, according to the dimensions of the research conceptual model, questions related to research questions were considered as the item for analysis in the modeling of structural equations. In the next step, 278 employees and managers of interest-free institutions were selected, by simple random sampling method, to answer the questionnaire. Data collected is analyzed by using structural equations method.

Findings

The results of the analysis indicates that the impact of the dimensions of strategic, technical, organizational and cultural factors – identified as the main characteristics of a financial system in this study – on the transparency of the transactions of the interest-free institutions is significant.

Research limitations/implications

The results were obtained by focusing on the qualitative factors and also on the culture on free-interest institutions.

Practical implications

By investigating the issues and factors that the developers, consultants and institutions’ managers need to address and also giving a conceptual model, this study assists managers and generally financial institutions in developing an integrated banking system in a way that will be more likely to improve transparency in those organizations.

Originality/value

This study pioneers a comprehensive conceptual model, surpassing prior research that focused on isolated criteria. This novel approach enriches understanding of core banking systems' impact on financial transparency. This groundbreaking study uniquely focuses on free-interest institutions, traditionally presumed to be transparent but never before studied.

Details

International Journal of Islamic and Middle Eastern Finance and Management, vol. 17 no. 5
Type: Research Article
ISSN: 1753-8394

Keywords

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Article
Publication date: 19 June 2019

Vahid Jaferian, Davood Toghraie, Farzad Pourfattah, Omid Ali Akbari and Pouyan Talebizadehsardari

The purpose of this study is three-dimensional flow and heat transfer investigation of water/Al2O3 nanofluid inside a microchannel with different cross-sections in two-phase mode.

326

Abstract

Purpose

The purpose of this study is three-dimensional flow and heat transfer investigation of water/Al2O3 nanofluid inside a microchannel with different cross-sections in two-phase mode.

Design/methodology/approach

The effect of microchannel walls geometry (trapezoidal, sinusoidal and stepped microchannels) on flow characteristics and also changing circular cross section to trapezoidal cross section in laminar flow at Reynolds numbers of 50, 100, 300 and 600 were investigated. In this study, two-phase water/Al2O3 nanofluid is simulated by the mixture model, and the effect of volume fraction of nanoparticles on performance evaluation criterion (PEC) is studied. The accuracy of obtained results was compared with the experimental and numerical results of other similar papers.

Findings

Results show that in flow at lower Reynolds numbers, sinusoidal walls create a pressure drop in pure water flow which improves heat transfer to obtain PEC < 1. However, in sinusoidal and stepped microchannel with higher Reynolds numbers, PEC > 1. Results showed that the stepped microchannel had higher pressure drop, better thermal performance and higher PEC than other microchannels.

Originality/value

Review of previous studies showed that existing papers have not compared and investigated nanofluid in a two-phase mode in inhomogeneous circular, stepped and sinusoidal cross and trapezoidal cross-sections by considering the effect of changing channel shape, which is the aim of the present paper.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 4 August 2021

Asieh Bakhtiar, Seyed Sepehr Ghazinoory, Alireza Aslani and Vahid Mafi

The purpose of this paper is to present and evaluate the performance of innovation systems by considering two indicators of efficiency and effectiveness. The scope of the…

465

Abstract

Purpose

The purpose of this paper is to present and evaluate the performance of innovation systems by considering two indicators of efficiency and effectiveness. The scope of the evaluation is globally and due to the situation of each country, the suggested strategies are proposed to maintain the status quo or move toward the desired situation for countries.

Design/methodology/approach

The approach is to compare and benchmark the countries in terms of the efficiency and effectiveness of their innovation system. The Global Innovation Index report’s input-to-output ratio and the global competitiveness report are used for the assessment.

Findings

The findings indicate that countries such as China, Switzerland and the USA have an efficient and effective innovation system. However, the innovation systems in countries such as Brazil and Zimbabwe are not only inefficient but also ineffective. The findings also indicate that the innovation systems of countries such as Iran, Armenia and Egypt are efficient but ineffective. Finally, the authors can name Australia, Qatar and Russia as countries with effective but inefficient innovation systems.

Originality/value

Assessment of national innovation system using efficiency and effectiveness performances is done for the first time at the global stage.

Details

Journal of Science and Technology Policy Management, vol. 13 no. 3
Type: Research Article
ISSN: 2053-4620

Keywords

Available. Open Access. Open Access

Abstract

Details

Journal of Intelligent Manufacturing and Special Equipment, vol. 4 no. 1
Type: Research Article
ISSN: 2633-6596

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Article
Publication date: 17 April 2019

Erfan Khodabandeh, Davood Toghraie, A. Chamkha, Ramin Mashayekhi, Omidali Akbari and Seyed Alireza Rozati

Increasing heat transfer rate in spiral heat exchangers is possible by using conventional methods such as increasing number of fluid passes and counter flowing. In addition, newer…

212

Abstract

Purpose

Increasing heat transfer rate in spiral heat exchangers is possible by using conventional methods such as increasing number of fluid passes and counter flowing. In addition, newer ideas such as using pillows as baffles in the path of cold and hot fluids and using nanofluids can increase heat transfer rate. The purpose of this study is to simulate turbulent flow and heat transfer of two-phase water-silver nanofluid with 0-6 Vol.% nanoparticle concentration in a 180° path of spiral heat exchanger with elliptic pillows.

Design/methodology/approach

In this simulation, the finite volume method and two-phase mixture model are used. The walls are subjected to constant heat flux of q″ = 150,000 Wm−2. The inlet fluid enters curves path of spiral heat exchanger with uniform temperature Tin = 300 K. After flowing past the pillows and traversing the curved route, the working fluid exchanges heat with hot walls and then exits from the section. In this study, the effect of radiation is disregarded because of low temperature range. Also, temperature jump and velocity slipping are disregarded. The effects of thermophoresis and turbulent diffusion on nanofluid heat transfer are disregarded. By using finite volume method and two-phase mixture model, simulations are performed.

Findings

The results show that the flow and heat transfer characteristics are dependent on the height of pillows, nanoparticle concentration and Reynolds number. Increasing Reynolds number, nanoparticle concentration and pillow height causes an increase in Nusselt number, pressure drop and pumping power.

Originality/value

Turbulent flow and heat transfer of two-phase water-silver nanofluid of 0-6 per cent volume fraction in a 180° path of spiral heat exchanger with elliptic pillows is simulated.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

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