Search results

1 – 10 of 41
To view the access options for this content please click here
Article
Publication date: 9 April 2018

Alaa Mohamed, Mohamed Hamdy, Mohamed Bayoumi and Tarek Osman

To enhance the tribological properties of nanogrease, one of the new technologies was used to synthesize a nanogrease having carbon nanotubes (CNTs) nanoparticles (NPs…

Abstract

Purpose

To enhance the tribological properties of nanogrease, one of the new technologies was used to synthesize a nanogrease having carbon nanotubes (CNTs) nanoparticles (NPs) with different concentrations. The microstructures of the synthesized NPs were characterized and evaluated by x-ray diffraction spectroscopy (XRD) and transmission electron microscopy (TEM). Tribological properties of the nanogrease were evaluated using a four-ball tester. The worn surface of four steel balls was investigated by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX).

Design/methodology/approach

Grease was dissolved in chloroform (10 Wt.%), at 25 °C for 1 h. In parallel, functionalized CNTs with different volume concentrations (0.5, 1, 2 and 3 Wt.%) were dispersed in N, N-dimethylformamide. The mixture was stirred for 15 min and then sonicated (40 kHz, 150 W) for 30 min. After that, the mixture was added to the grease solution and magnetically stirred for 15 min and then sonicated for 2 h.

Findings

The results suggested that CNTs can enhance the antiwear and friction properties of nanogrease at 0.5 Wt.% CNTs to about 57 and 48 per cent, respectively. In addition, the weld load of the base oil containing 0.5 Wt.% CNTs was improved by 17 per cent compared with base grease.

Originality/value

This work describes the inexpensive and simple fabrication of nanogrease for improving the properties of lubricants, which improve power efficiency and extend lifetimes of mechanical equipment.

Details

Industrial Lubrication and Tribology, vol. 70 no. 3
Type: Research Article
ISSN: 0036-8792

Keywords

To view the access options for this content please click here
Article
Publication date: 10 July 2017

Alaa Mohamed, Mohamed Hamdy, Mohamed Bayoumi and Tarek Osman

This work describes the fabrication of composite nanogrease based on carbon nanotubes (CNTs) as an additive at different volume concentrations 0, 0.5, 1, 2 and 3 Wt.% and…

Abstract

Purpose

This work describes the fabrication of composite nanogrease based on carbon nanotubes (CNTs) as an additive at different volume concentrations 0, 0.5, 1, 2 and 3 Wt.% and investigates the correlation between CNTs and grease rheological behaviour. In addition, study the influence of shear thinning rate at various temperatures and investigates the thermal conductivity of nanogrease. The results demonstrated that grease behaves like a Newtonian viscoelastic material with a narrow linear domain. The thermal conductivity of nanogrease was enhanced by about 31.58 per cent, and the thermal and mechanical stabilities improved. Moreover, the apparent viscosity and dropping point increased by about 93 and 27 per cent, respectively.

Design/methodology/approach

Grease was dissolved in chloroform (10 Wt.%), at 25°C for 1 h. In parallel, functionalized CNTs with different volume concentrations (0.5, 1, 2 and 3 Wt.%) were dispersed in N,N-dimethylformamide; the dispersion was stirred for 15 min, and then sonicated (40 kHz, 150 W) for 30 min. Grease solution was then added to the CNTs. The nanofluid was magnetically stirred for 15 min and then sonicated for 2 h. This ensured uniform dispersion of nanoparticles in the base fluid.

Findings

Inexpensive and simple fabrication of nanogrease. Thermal conductivity of nanogrease was typically enhanced compared to other reported studies. Apparent viscosity and dropping point increases with the increase the volume concentration.

Originality/value

This work describes the inexpensive and simple fabrication of nanogrease for improving properties of lubricants, which improve power efficiency and extend lifetimes of mechanical equipment.

Details

Industrial Lubrication and Tribology, vol. 69 no. 4
Type: Research Article
ISSN: 0036-8792

Keywords

To view the access options for this content please click here
Article
Publication date: 28 May 2021

Mahmoud Abdelrahman Kamel, Mohamed El-Sayed Mousa and Randa Mohamed Hamdy

This study used data envelopment analysis (DEA) models to measure financial efficiency of twelve commercial banks listed in the Egyptian stock exchange (CBLSE), along with…

Abstract

Purpose

This study used data envelopment analysis (DEA) models to measure financial efficiency of twelve commercial banks listed in the Egyptian stock exchange (CBLSE), along with evaluating changes to the financial efficiency during the period 2017–2019.

Design/methodology/approach

The study used BCC-I, cross-efficiency, super-efficiency models, and Malmquist productivity index (MPI) to assess financial efficiency of the examined banks. The available data from both inputs and outputs were analyzed using R. studio V.I.3. 1056 software.

Findings

Out of twelve banks examined, only four banks were efficient under BCC-I model over different years of the study period; however, only one bank (CIB) appeared to be the most efficient compared to other peers in the study sample. Moreover, MPI results revealed decreased financial efficiency during the study period, due to the decreased technological innovation, except for HDB. Tobit regression results confirmed that total assets and total equity are significant factors impacted financial efficiency of CBLSE.

Practical implications

This study sheds light on the importance of evaluating financial efficiency of CBLSE to all stakeholders, to pinpoint weaknesses in banks' performance, and for evaluating financial policies and investment decisions.

Originality/value

Several studies sought to implement different models of DEA to assess banking performance in different regions of the world, but very few studies examined financial efficiency of banks. To the best of authors’ knowledge, this study is one of those few that addressed financial efficiency of banks in Egypt.

Details

International Journal of Productivity and Performance Management, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1741-0401

Keywords

To view the access options for this content please click here
Article
Publication date: 1 March 1996

Ayech Benjeddou and Mohamed Ali Hamdi

Presents a new B‐spline finite element for the dynamic analysis of unsymmetrical sandwich shells of revolution. The formulation takes account of the membrane and bending…

Abstract

Presents a new B‐spline finite element for the dynamic analysis of unsymmetrical sandwich shells of revolution. The formulation takes account of the membrane and bending effects in isotropic or orthotropic elastic facings, and membrane, bending and transverse shearing effects in an isotropic or othotropic elastic core. Both geometry and local displacements are interpolated by a set of B‐spline functions. The main aspects added by the sandwich structure of the element are the transverse shearing and membrane‐bending coupling effects in the core. These are well represented by a set of new variables which are the mean end relative in‐plane displacements of the facing middle surfaces. Together with the transverse displacement, these variables constitute the degrees of freedom (dofs) of this new B‐spline sandwich element. The finite elements are grouped into super‐elements with C1 continuity to obtain the whole finite element model. For each super‐element a total of five dofs per node is then obtained except for its end nodes where the derivatives of these dofs with respect to the meridional co‐ordinate are added. This choice reduces to a minimum the total number of dofs in comparison to existing sandwich elements. Evaluates the efficiency and accuracy of the proposed element through several benchmark examples. Compares the results with the analytical and numerical solutions found in the literature. A very satisfactory behaviour of the element was observed in all test cases.

Details

Engineering Computations, vol. 13 no. 2/3/4
Type: Research Article
ISSN: 0264-4401

Keywords

To view the access options for this content please click here
Article
Publication date: 3 February 2020

Anna Dimitrova, Tim Rogmans and Dora Triki

This paper aims to synthesize, analyze and categorize the empirical literature on country-specific factors that affect foreign direct investment (FDI) inflows to the…

Abstract

Purpose

This paper aims to synthesize, analyze and categorize the empirical literature on country-specific factors that affect foreign direct investment (FDI) inflows to the Middle East and North Africa (MENA) region. Identifying gaps and methodological challenges in the reviewed articles, recommendations are made to guide future research.

Design/methodology/approach

Applying the systematic review methodology, content analysis is conducted of 42 relevant empirical studies that explore country-specific FDI determinants in the MENA region during the period 1998–2018.

Findings

This review study identifies four main research gaps in the extant literature: a lack of consensus on a common definition of the MENA region and a weak understanding of the specificities of its investment environment; a limited set of FDI theories used and a lack of other theoretical perspectives; a recurrent focus on the direct relationship between host country–specific determinants and FDI, thus ignoring the moderating and mediating effects of some variables; and the absence of certain country-specific factors pertaining to the MENA countries.

Originality/value

This study contributes to the international business field by enhancing our understanding of the FDI determinants in emerging and developing markets, especially the MENA countries. It develops a typology of FDI country-specific factors in the MENA region based on four main categories: macroeconomic and financial, institutional and regulatory, natural resource endowment and socio-cultural. Paths for future research are suggested.

Details

Multinational Business Review, vol. 28 no. 1
Type: Research Article
ISSN: 1525-383X

Keywords

Content available
Article
Publication date: 1 June 2010

Matthew Clarke and James Pounder

Abstract

Details

Education, Business and Society: Contemporary Middle Eastern Issues, vol. 3 no. 2
Type: Research Article
ISSN: 1753-7983

To view the access options for this content please click here
Article
Publication date: 12 March 2018

Mohamed Ashour, Alaa Mohamed, Abou Bakr Elshalakany, Tarek Osman and Aly Khatab

The purpose of this paper is to investigate the rheological characteristics of graphene nanoplatelets (GNPs) and hybridized nanocomposite consisting of multi-walled carbon…

Abstract

Purpose

The purpose of this paper is to investigate the rheological characteristics of graphene nanoplatelets (GNPs) and hybridized nanocomposite consisting of multi-walled carbon nanotubes (MWCNTs) and GNPs as an additive on lithium-based grease. The experiments of nanogrease are examined in different values of shear stress, apparent viscosity, temperature and shear rate using Brookfield Programmable Rheometer DV-III ULTRA and characterized by high-resolution transmission electron microscope (HRTEM) and X-ray diffraction (XRD).

Design/methodology/approach

First, GNPs was mixed well with lithium grease using mechanical stirring at 3,500 rpm for 15 min at room temperature to form a homogenous composite at different concentrations (0.5, 1, 1.5, 2 and 2.5 Wt.%). Afterwards, MWCNTs and GNPs are mixed and dispersed well in the lithium grease using a sonication path for 30 min and mechanical stirring at 3,500 rpm for 15 min at 28°C to form a homogenous nanocomposite.

Findings

The results indicated that 1 Wt.% of GNPs is the optimum concentration. Subsequently, the weight percentage of additives varying between MWCNTs and GNPs are tested, and the result indicate that the grease containing GNPs had a 75 per cent increase in shear stress and 93.7 per cent increase in apparent viscosity over ordinary grease.

Originality/value

This work describes the inexpensive and simple fabrication of nanogrease for improving properties of lubricants, which improve power efficiency and extend lifetimes of mechanical equipment.

Details

Industrial Lubrication and Tribology, vol. 70 no. 2
Type: Research Article
ISSN: 0036-8792

Keywords

To view the access options for this content please click here
Article
Publication date: 17 August 2020

Fadi Alsarhan and Marc Valax

This paper aims to offer a review of the concept of wasta, as a form of social capital in Arab societies. Furthermore, this paper seeks to elucidate the main implications…

Abstract

Purpose

This paper aims to offer a review of the concept of wasta, as a form of social capital in Arab societies. Furthermore, this paper seeks to elucidate the main implications of the use of wasta among human resource management (HRM) practices on the workplace environment and the overall performance of institutions.

Design/methodology/approach

The authors embraced a qualitative approach in this paper. A total of 27 semi-structured interviews were conducted with HR officials from different levels in a number of Jordanian public organizations.

Findings

The results obtained indicate that wasta has negative consequences on the overall performance of organizations, through the influence it exerts on employee motivation, morale and job satisfaction, frustration, workplace diversity, turnover, brain drain, as well as its effect on the image and reputation of the individuals and organizations alike.

Originality/value

In this paper, the authors attempted to illustrate the concept of wasta as a form of social capital and to analyze its links with the features of the Jordanian culture through two of Hofstede’s dimensions. Furthermore, this paper is based both on the available literature and on data obtained through the semi-structured interviews. The findings through this process not only corroborate what we already know in the literature but they also generate an understanding of the hidden mechanisms that link the different implications of wasta together, creating the actual known consequences of this practice.

Details

International Journal of Islamic and Middle Eastern Finance and Management, vol. 14 no. 1
Type: Research Article
ISSN: 1753-8394

Keywords

To view the access options for this content please click here
Article
Publication date: 16 August 2019

Ahmed Mobasher, Alaa Khalil, Medhat Khashaba and Tarek Osman

The purpose of this paper is to evaluate the influence of nanoparticles as an additive on the tribological properties of calcium grease.

Abstract

Purpose

The purpose of this paper is to evaluate the influence of nanoparticles as an additive on the tribological properties of calcium grease.

Design/methodology/approach

The nano additives in this research are with different concentration of multi carbon nanotubes (MWCNTs) and Talc powder (1, 2, 3, 3 and 5 per cent). The ratio of MWCNTs to Talc powder is 1:1. The tribological properties of hyper MWCNTs/Talc powder to calcium grease were evaluated using a pin-on-disk wear testing. The results show that the nano additives MWCNTs/Talc to calcium grease exhibit good performance in anti-wear and friction reduction. The action mechanism was estimated through analysis of the worm surface with x-ray diffraction and transmission electron microscope.

Findings

The result indicates that boundary film mainly composed of MWCNT and Talc powder, and other organic compound was formed on the worm surface during the friction test. In addition, the wear rate and coefficient of friction of nanogreases have shown excellent improvement about 80.62 and 63.44 per cent, respectively, at 4 Wt.% of MWCNTs/Talc powder. Moreover, the thermal conductivity of nanogrease increased about 51.72 per cent.

Originality/value

This study describes the inexpensive and simple fabrication of nanogrease for improving properties of lubricants, which improve power efficiency and extend lifetimes of mechanical equipment.

Details

Industrial Lubrication and Tribology, vol. 72 no. 1
Type: Research Article
ISSN: 0036-8792

Keywords

To view the access options for this content please click here
Article
Publication date: 12 November 2018

Francisca Beer, Badreddine Hamdi and Mohamed Zouaoui

The purpose of this paper is to examine whether investors’ sentiment affects accruals anomaly across European countries.

Abstract

Purpose

The purpose of this paper is to examine whether investors’ sentiment affects accruals anomaly across European countries.

Design/methodology/approach

The authors estimate the model using Fama–MacBeth regressions. The sample includes 54,572 firm-year observations for 4,787 European firms during the period 1994–2014.

Findings

The authors find that investors’ sentiment influences accruals mispricing across European countries. The effect is pronounced for stocks whose valuations are highly subjective and difficult to arbitrage. The cross-country analysis provides evidence that sentiment influences accruals anomaly in countries with weaker outside shareholder rights, lower legal enforcement, lower equity market development, higher allowance of accrual accounting and in countries where herd-like behavior and overreaction behavior are strong.

Research limitations/implications

The findings suggest the generalizability of the sentiment-accruals anomaly relation in European countries characterized by different cultural values, levels of economic development and legal tradition.

Practical implications

The findings suggest to caution individuals investors. These investors would be wise to take into account the impact of sentiment on the performance of their portfolio. They must keep in mind that periods of high optimism are accompanied by a high level of accruals and followed by low future stock returns.

Originality/value

The research supplements previous American studies by showing the significance of the level of sentiment in understanding the accruals anomaly in Europe. Hence, it is important for future studies to consider investor sentiment as an important time-series determinant of the accruals anomaly, particularly for stocks that are hard to value and difficult to arbitrage.

Details

Journal of Applied Accounting Research, vol. 19 no. 4
Type: Research Article
ISSN: 0967-5426

Keywords

1 – 10 of 41