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1 – 10 of over 1000
Article
Publication date: 3 January 2019

Alireza Ghayour and Mahmoud Mani

The purpose of this paper is to compare the effects of two different configurations of plasma streamwise vortex generators (PSVG), including comb-type and mesh-type in…

Abstract

Purpose

The purpose of this paper is to compare the effects of two different configurations of plasma streamwise vortex generators (PSVG), including comb-type and mesh-type in controlling flow. This is demonstrated on the NACA 0012 airfoil.

Design/methodology/approach

The investigations have been done experimentally at the various electric and aerodynamic conditions. The surface oil flow visualization method has been used to the better understanding of the flow physics and the interaction of the oncoming flow passing over the airfoil and the vortex generated by comb-type PSVG.

Findings

This paper demonstrates the potential capabilities of the mesh-type and comb-type PSVGs in controlling flow in unsteady operation. It was found that the vortex generated by the mesh-type PSVG in unsteady operation was an order of magnitude stronger than comb-type PSVG. The flow visualisation technic proved that only a part of the plasma actuator is effective in the condition that the actuator is installed only on a portion of the upper surface of the airfoil.

Originality/value

This paper experimentally confirms the capabilities of the mesh-type PSVG unsteady operation in compare with comb-type PSVG in controlling flow, whereby recommends using mesh-type PSVG in the leading edge in front of comb-type PSVG on the entire wingspan to prevent the stall.

Details

Aircraft Engineering and Aerospace Technology, vol. 92 no. 3
Type: Research Article
ISSN: 1748-8842

Keywords

Article
Publication date: 1 January 2014

Fariba Ajalli and Mahmoud Mani

The main aim of the present work is to examine the effects of trailing edge strip (TES) on the wake region of a plunging airfoil that oscillates prior and beyond the…

Abstract

Purpose

The main aim of the present work is to examine the effects of trailing edge strip (TES) on the wake region of a plunging airfoil that oscillates prior and beyond the static stall angle of attack.

Design/methodology/approach

In this study, experimental investigations were carried out to explore the wake characteristics of a plunging Eppler 361airfoil equipped with TES flap. The experiments involved measurements of flapped and unflapped airfoil wake velocity for the range of initial AOA (0 and 12°). Surface pressure measurements as a supplementary data were also carried out. Data were taken at reduced frequencies of 0.03 and 0.073 and different distances downstream from trailing edge.

Findings

The results showed the hysteresis between the plunging wake in the upstroke and down-stroke motion. When the airfoil oscillated beyond the static stall angle of attack, huge variations on the wake profiles were found because of the interaction between LEV and Von Kármán vortices. More velocity defect in the wake region was realized by adding the TES but this effect was not the same for different phases of oscillation cycle. Also the power spectra of dominant frequencies and the extension of wake vortices were significantly increased by fitting the TES on the plunging airfoil.

Practical implications

The knowledge of the present study is necessary to enhance the performance of wind turbines, rotorcraft blades and maneuvering aircraft.

Originality/value

To date, no investigation has been conducted to determine the effects of a TES on the plunging airfoil aerodynamics.

Details

Aircraft Engineering and Aerospace Technology: An International Journal, vol. 86 no. 1
Type: Research Article
ISSN: 0002-2667

Keywords

Article
Publication date: 6 July 2010

Hamed Sadeghi, Mahmoud Mani and S.M. Hossein Karimian

The primary purpose of this paper is to investigate the characteristics of the unsteady flow field in the wake of Eppler‐361 airfoil undergoing harmonic pitch oscillation…

1086

Abstract

Purpose

The primary purpose of this paper is to investigate the characteristics of the unsteady flow field in the wake of Eppler‐361 airfoil undergoing harmonic pitch oscillation in both pre‐stall and post‐stall regimes.

Design/methodology/approach

Experimental measurements were carried out to study the characteristics of the unsteady flow field within the wake of an airfoil. All of the experiments were conducted in a low‐speed wind tunnel, and the velocity field was measured by a hot‐wire anemometry. The airfoil was given a harmonic pitching motion about its half chord axis at two reduced frequencies of 0.091 and 0.273. All experimental data were taken at the oscillation amplitude of 8°. During the experiments, the mean angle of attack was altered from 2.5 to 10° that this made it possible to study the wake in both pre‐stall and post‐stall regimes.

Findings

From the results, it can be concluded that different velocity profiles are formed in the wake at different phase angles. In addition, the hysteresis of the velocity field in the wake is captured between increasing and decreasing incidences. It is also found that the velocity field in the wake is strongly affected by the operating conditions of the airfoil, e.g. mean angle of attack, reduced frequency and instantaneous angle of attack. Huge variations in the profiles of the wake are observed at high instantaneous angles of attack when the mean angle of attack is 10°, i.e. when the airfoil experiences significant oscillations beyond the static stall. It is concluded that this is due to dynamic stall phenomenon.

Practical implications

Findings of the present study give valuable information, which can be used to characterize wakes of micro air vehicles, helicopter's rotor blades, and wind turbine blades. In addition to this, present findings can be used to predict dynamic stall of the above applications.

Originality/value

The paper is the first to investigate the unsteady wake of Eppler‐361 airfoil and to predict the dynamic stall phenomenon of this airfoil.

Details

Aircraft Engineering and Aerospace Technology, vol. 82 no. 4
Type: Research Article
ISSN: 0002-2667

Keywords

Article
Publication date: 4 July 2008

Kamran Raissi, Mahmoud Mani, Mehdi Sabzehparvar and Hooyar Ghaffari

This paper aims to investigate the addition of airdrop capability to a commuter aircraft and its consequences on the reversible flight control system.

Abstract

Purpose

This paper aims to investigate the addition of airdrop capability to a commuter aircraft and its consequences on the reversible flight control system.

Design/methodology/approach

Airdrop was modeled to include its effect on aerodynamics and flight control system. A mathematical model was also developed for the reversible longitudinal flight control system of a regional commuter aircraft using the available geometry, mass property and kinematics. The model was incorporated into a general multi‐body dynamics code and validated using existing manufacturer's data which included recorded data from flight. The airdrop simulation results showed that the flight control system is affected in two steps. In the first step, the movement of the load required a forward force by the pilot. In this step, the elevator power was a key factor and had to be increased to allow the pilot to keep the aircraft in trim position during the airdrop. In the second step, a sudden forward shift of centre of gravity required an abrupt change in the direction of applied force. The maximum allowable force and control column movement had to be checked. In the case under study, they did not impose any difficulty.

Findings

The result showed that a special consideration had to be taken into account when an aircraft with reversible flight control system was to be used for airdrop mission.

Originality/value

This paper investigates the behaviour of a reversible flight control system during airdrop operation through analysis and simulation.

Details

Aircraft Engineering and Aerospace Technology, vol. 80 no. 4
Type: Research Article
ISSN: 0002-2667

Keywords

Article
Publication date: 18 September 2019

Seemant Kumar Yadav, Vikas Tripathi and Geetika Goel

The purpose of this paper is to identify and rank different dimensions of strategic orientation and firm’s performance using the approach of interpretive structural modeling.

Abstract

Purpose

The purpose of this paper is to identify and rank different dimensions of strategic orientation and firm’s performance using the approach of interpretive structural modeling.

Design/methodology/approach

The study uses interpretative structural modeling and the MICMAC technique to establish a hierarchical relationship among different dimensions of entrepreneurial orientation and manufacturing performance of Indian SMEs.

Findings

The final outcome of interpretative structural modeling and the MICMAC analysis revealed a relationship between the variables under study along with the categorization of all in two different categories, depending upon their driving power and dependency, which decision-makers can also use while devising their strategy to improve performance.

Originality/value

To date, to the best of the authors’ knowledge, no significant contribution about such interrelationship was reported; therefore, this study is one of its types to fill this gap.

Details

Journal of Modelling in Management, vol. 14 no. 3
Type: Research Article
ISSN: 1746-5664

Keywords

Executive summary
Publication date: 23 January 2018

IRAN: Financial-sector woes could spark new protests

Details

DOI: 10.1108/OXAN-ES229264

ISSN: 2633-304X

Keywords

Geographic
Topical
Open Access
Article
Publication date: 22 April 2022

Mahmoud Ahmad Mahmoud, Shuhymee bin Ahmad and Donny Abdul Latief Poespowidjojo

The purpose of this study is to assess the validity of the psychological safety (PS), psychological empowerment (PE), intrapreneurial behaviour (IB) and individual…

Abstract

Purpose

The purpose of this study is to assess the validity of the psychological safety (PS), psychological empowerment (PE), intrapreneurial behaviour (IB) and individual performance (IP) construct measurements originally developed in Western individualistic cultures.

Design/methodology/approach

Proportionate stratified systematic sampling was used among the production/operations middle managers in Nigerian medium enterprises (MEs), resulting in 355 valid responses. The measurements were analysed through internal consistency analysis, content, convergent and discriminant validity analysis.

Findings

The result shows that all four construct measurements are suitable and appropriate to gauge the respective constructs in collectivistic cultures such as Nigeria.

Research limitations/implications

Cross-sectional self-reported data were used to analyse the result of this study, which may lead to common method variance.

Practical implications

Organizations, especially MEs, can use the validated measurements of this study to enhance work results in the Nigerian context.

Social implications

Collectivistic cultures can benefit from the widely used measurements of PS, PE, IB and IP despite been originally developed in Western individualistic cultures.

Originality/value

This paper extends the body of knowledge by validating the measurements of PS, PE, IB and IP in collectivistic cultures such as Nigeria. Measurement validation for these constructs is scarce in this context. Thus, this study will provide a consistent and efficient reference for forthcoming studies and improve the credibility and replicability of future research results in collectivistic cultures.

Details

RAUSP Management Journal, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 2531-0488

Keywords

Article
Publication date: 31 May 2021

Mahmoud Ahmad Mahmoud, Shuhymee Ahmad and Donny Abdul Latief Poespowidjojo

The purpose of this study is to extend the existing literature on the relationship between psychological empowerment and individual performance (IP) through the mediating…

Abstract

Purpose

The purpose of this study is to extend the existing literature on the relationship between psychological empowerment and individual performance (IP) through the mediating role of intrapreneurial behaviour (IB). Therefore, the empowerment theory (ET) and psychological entrepreneurship theory (PET) were integrated to nurture the IP of medium enterprises (MEs) production/operations managers by analyzing the mediating influence of IB on the psychological empowerment–IP relationship.

Design/methodology/approach

Survey method was engaged by means of self-administered questionnaire. Data were collected from a sample of 355 MEs production/operations managers and analysed with partial least square (PLS) structural equation modelling (SEM).

Findings

According to the results, Psychological empowerment (PE) has a significant direct relationship with both IB and IP. Equally, IB has a positive significant impact on IP. Moreover, the mediating influence of IB on the psychological empowerment–IP relationship was established.

Practical implications

The result implies that MEs can stimulate the IP of production/operations managers by encouraging IB through psychological empowerment–IP relationship. Therefore, the psychological empowerment–IP relationship will manifest better when IB is invigorated among production/operations managers.

Originality/value

To the best of the authors’ knowledge, this paper is the first to examine the mediating influence of IB on the psychological empowerment–IP relationship, which revealed a significant contribution to both entrepreneurship and organizational behaviour literature. The IB literature is relatively lacking, particularly among developing countries and in particular Nigeria.

Details

European Journal of Innovation Management, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1460-1060

Keywords

Article
Publication date: 29 April 2021

Mahmoud Ahmad Mahmoud, Shuhymee Ahmad and Donny Abdul Latief Poespowidjojo

The objective of this paper is to extend the extant literature on the relationship between psychological safety (PS) and individual performance (IP) through the mediating…

Abstract

Purpose

The objective of this paper is to extend the extant literature on the relationship between psychological safety (PS) and individual performance (IP) through the mediating influence of intrapreneurial behavior (IB). Therefore, the social exchange theory (SET) and psychological entrepreneurship theory (PET) are integrated to achieve this objective.

Design/methodology/approach

Survey method of data collection was engaged through self-administered questionnaire. The sample of 355 medium enterprises (MEs) production/operations managers was analyzed by means of partial least square (PLS) structural equation modeling (SEM).

Findings

The result shows that PS has a significant direct relationship with both IP and IB; likewise, IB has a significant positive influence on IP. The mediating influence of IB on the PS–IP relationship was also confirmed.

Practical implications

The result suggests that PS–IP relationship will be better explained when IB is fortified among managers. Therefore, MEs could stimulate production/operations manager performance by encouraging IB through PS–IP relationship.

Originality/value

To the authors’ knowledge, this paper is the first to study the influence of individual-level PS on the complete individual-level IB and the mediating influence of individual IB on PS–IP relationship. Moreover, the intraprenerurship literature is relatively lacking expressly among developing countries and precisely Nigeria. As such, the attention of researchers is important on the role of individual-level IB in MEs against the assumption that entrepreneurial events are limited to firm-level concerns.

Details

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

Keywords

Article
Publication date: 6 June 2019

Ali Bassam Mahmoud, Nicholas Grigoriou, Leonora Fuxman, Dieu Hack-Polay, Fatina Bassam Mahmoud, Eiad Yafi and Shehnaz Tehseen

This study aims to assess consumers’ beliefs in three Middle Eastern Arab countries regarding attitudinal and behavioural responses towards permission-based direct email…

2073

Abstract

Purpose

This study aims to assess consumers’ beliefs in three Middle Eastern Arab countries regarding attitudinal and behavioural responses towards permission-based direct email marketing (hereafter DEM) and the moderating role of gender in the hypothesised path model.

Design/methodology/approach

Structural equation modelling was used to test the hypothesised path model by using data collected from 829 respondents.

Findings

The findings show that attitude was found to fully mediate the relationship between beliefs and behavioural responses towards permission-based DEM. Gender moderates the relationship between beliefs and attitudes and responses to permission-based DEM. Notably, female respondents were found to react more actively when exposed to permission-based DEM.

Research limitations/implications

Further qualitative research is needed to learn more about how and why individuals develop behavioural intentions in certain ways towards opt-in DEM. In addition, neuropsychology approaches such as eye-tracking are endorsed for future research to gain more insights and conquer biases associated with self-reporting procedures in countries where such technologies are deemed as legal and ethical to be used with human subjects.

Practical implications

Advertisers promoting products and services in the Middle Eastern Arab context should take further steps to enhance the quality of information (including cultural sensitiveness) and the perceived entertainment value that could be delivered to consumers through permission-based DEM, especially for female internet users. Additionally, this study highly recommends the double opt-in approach to permission-based DEM.

Originality/value

To the best of the authors’ knowledge, this is the first attempt to address the gender role as a moderator of the path depicting the effectiveness of permission-based DEM approach in the Middle East (Arab counties) from beliefs to behavioural responses via attitudes.

Details

Journal of Research in Interactive Marketing, vol. 13 no. 2
Type: Research Article
ISSN: 2040-7122

Keywords

1 – 10 of over 1000