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…
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.
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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…
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.
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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.
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.
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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…
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.
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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…
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.