Fuad M. Khoshnaw and Namam M. Ahmed
The purpose of this paper is to investigate the effect of pressure angle, and module of spur gear teeth on stress concentration factor, using photoelasticity method, and numerical…
Abstract
Purpose
The purpose of this paper is to investigate the effect of pressure angle, and module of spur gear teeth on stress concentration factor, using photoelasticity method, and numerical MSC/NASTRAN finite element package.
Design/methodology/approach
The stress concentration factor is determined as a ratio between maximum stress (determined in the fillet radius by photoelastic and finite element methods), and nominal stress (calculated by a common standard formulas). In order to specify the geometric parameters (height and thickness) of gears, both standard Deutsches Institut für Normung (DIN)/Japanese Gear Manufactures Association (JGMA), and five other non‐standard approaches are used.
Findings
The results show that the stress concentration factor increases by decreasing the pressure angle. In addition, the values which are obtained by finite element analyses exhibit more uniformity than photoelastic method.
Practical implications
An accurate determination of stress concentration factors will limit both over and under design of the gears.
Originality/value
The results show that one of the suggested non‐standard approaches gives the highest stress concentration factor than the standard approaches.
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Citizens are substantial stakeholders in every e-government system, thus their willingness to use and ability to access the system are critical. Unequal access and information and…
Abstract
Citizens are substantial stakeholders in every e-government system, thus their willingness to use and ability to access the system are critical. Unequal access and information and communication technology usage, which is known as digital divide, however has been identified as one of the major obstacles to the implementation of e-government system. As digital divide inhibits citizen’s acceptance to e-government, it should be overcome despite the lack of deep theoretical understanding on this issue. This research aimed to investigate the digital divide and its direct impact on e-government system success of local governments in Indonesia as well as indirect impact through the mediation role of trust. In order to get a comprehensive understanding of digital divide, this study introduced a new type of digital divide, the innovativeness divide.
The research problems were approached by applying two-stage sequential mixed method research approach comprising of both qualitative and quantitative studies. In the first phase, an initial research model was proposed based on a literature review. Semi-structured interview with 12 users of e-government systems was then conducted to explore and enhance this initial research model. Data collected in this phase were analyzed with a two-stage content analysis approach and the initial model was then amended based on the findings. As a result, a comprehensive research model with 16 hypotheses was proposed for examination in the second phase.
In the second phase, quantitative method was applied. A questionnaire was developed based on findings in the first phase. A pilot study was conducted to refine the questionnaire, which was then distributed in a national survey resulting in 237 useable responses. Data collected in this phase were analyzed using Partial Least Square based Structural Equation Modeling.
The results of quantitative analysis confirmed 13 hypotheses. All direct influences of the variables of digital divide on e-government system success were supported. The mediating effects of trust in e-government in the relationship between capability divide and e-government system success as well as in the relationship between innovativeness divide and e-government system success were supported, but was rejected in the relationship between access divide and e-government system success. Furthermore, the results supported the moderating effects of demographic variables of age, residential place, and education.
This research has both theoretical and practical contributions. The study contributes to the developments of literature on digital divide and e-government by providing a more comprehensive framework, and also to the implementation of e-government by local governments and the improvement of e-government Readiness Index of Indonesia.
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Nigar Ahmed and Mou Chen
The purpose of this research paper is to design a disturbance observer-based control based on the robust model reference adaptive backstepping sliding-mode control for attitude…
Abstract
Purpose
The purpose of this research paper is to design a disturbance observer-based control based on the robust model reference adaptive backstepping sliding-mode control for attitude quadrotor model subject to uncertainties and disturbances.
Design/methodology/approach
To estimate and reject the disturbance, a disturbance observer is designed for the exogenous disturbances with perturbation while a control criterion is developed for the tracking of desired output. To achieve the control performance, backstepping and sliding-mode control techniques are patched together to obtain robust chattering-free controller. Furthermore, a model reference adaptive control criterion is also combined with the design of robust control for the estimation and rejection of uncertainties and unmodeled dynamics of the attitude quadrotor.
Findings
The findings of this research work includes the design of a disturbance observer-based control for uncertain attitude quadrotor system with the ability of achieving tracking control objective in the presence of nonlinear exogenous disturbance with and without perturbation.
Practical implications
In practice, the quadrotor flight is opposed by different kinds of the disturbances. In addition, being an underactuated system, it is difficult to obtain an accurate mathematical model of quadrotor for the control design. Thus, a quadrotor model with uncertainties and disturbances is inevitable. Hence, it is necessary to design a control system with the ability to achieve the control objectives in the presence of uncertainties and disturbances.
Originality/value
Designing the control methods for quadrotor control without uncertainties and disturbances is a common practice. However, investigating the uncertain quadrotor plant in the presence of nonlinear disturbances is rarely taken into consideration for the control design. Hence, this paper presents a control algorithm to address the issues of the uncertainties and disturbances as well as investigate a control algorithm to achieve tracking performance.
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Salwa H. El-Sabbagh, Doaa Samir Mahmoud, Nivin M. Ahmed, A.A. Ward and Magdy Wadid Sabaa
This paper aims to study the role of organobentonite (OB) as a filler to improve the mechanical strength of styrene butadiene rubber (SBR). Organoclay was first prepared by…
Abstract
Purpose
This paper aims to study the role of organobentonite (OB) as a filler to improve the mechanical strength of styrene butadiene rubber (SBR). Organoclay was first prepared by modifying bentonite with different concentrations of N-cetyl-N, N, N-triethyl ammonium bromide. A series of SBR composites reinforced with OB were prepared using master-batch method.
Design/methodology/approach
The curing characteristics, mechanical properties, thermal behavior, dielectric properties and morphology of SBR/OB composites were investigated.
Findings
The elastic modulus and tensile strength of composites were increased by inclusion of OB, while the elongation at break was decreased, due to the increase in the degree of cross-linking density. Thermal gravimetric analysis revealed an improvement in the thermal stability of the composite containing 0.5 cation exchange capacity (CEC) OB, while the scanning electron micrographs confirmed more homogenous distribution of 0.5CEC OB in the rubber matrix. Also, SBR/0.5CEC OB showed low relative permittivity and electrical insulating properties.
Research limitations/implications
Bentonite has been recognized as a potentially useful filler in polymer matrix composites because of their high swelling capacity and plate morphology.
Practical implications
OB improves the cured rubber by increasing the tensile strength and the stiffness of the vulcanizate.
Social implications
Using cheap clay in rubber industry lead to production of low cost products with high efficiency.
Originality/value
The clay represents a convenient source because of their environmental compatibility. The low cost and easy availability make the modified clay used as fillers in rubber matrices, and the resultant composites can be applied in variety industrial of applications such as automobile industries, shoe outsoles, packaging materials and construction engineering.
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Hoong Sang Wong and Chen Chen Yong
This chapter provided systematic and comprehensive analysis on trawl fisheries management and conservation measures in the Straits of Malacca. Detailed analysis is conducted on…
Abstract
This chapter provided systematic and comprehensive analysis on trawl fisheries management and conservation measures in the Straits of Malacca. Detailed analysis is conducted on Malaysian fishery management framework particularly domestic country's trawl fishery status, legal structure, input-control strategies, ecosystem protection plan, pollution, law enforcement, and complementary measures that designed to reduce and prevent overfishing in the exclusive economic zone (EEZ) of Malacca Straits. Gaps and challenges found in existing trawl fisheries literature are presented followed by recommendations for improvement in the management and conservation of trawl fisheries.
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Mohammed Soliman Aly Khedr, Mona Foad Ali, Ahmed Nabil Emam, Abdullah Mahmoud Kamel and Manal Abdel-Monem Ghanam
This study aims to provide an efficient nanocomposite that might be used to protect deteriorated archaeological stucco.
Abstract
Purpose
This study aims to provide an efficient nanocomposite that might be used to protect deteriorated archaeological stucco.
Design/methodology/approach
The current experimental study evaluates the effectiveness of the hydroxyapatite nanoparticles (HA NPs) added to graphite carbon nitride (g-C3N4) and mixed with Paraloid (B-72) (B-44) in acetone in consolidating samples. The physicochemical properties of the as-prepared nanopowders have been investigated using Fourier transform infrared (FT-IR). This study involves monitoring the transmission electron microscope (TEM), X-ray diffraction (XRD) and Fourier transform changes in consolidated samples after exposure to various conditions by using the digital microscope and scanning electron microscopy to identify the appearance of the consolidated stucco samples after applying the selected nanocomposites and after their artificial aging procedures. Color change is measured using a colorimeter, and comparisons are made between samples before and after aging. Physical and mechanical properties are determined, and the contact angle is measured to measure hydrophobicity rate.
Findings
The obtained results indicate that HA/g-C3N4 hybrid nanocomposites with a composition of HA 0.5%/g-C3N4 1%/B-72 3% and HA 0.5%/g-C3N4 1%/B-44 3% achieved the best consolidating results among the proposed mixtures for stucco samples, where the percentage of weight loss was 0.77 with B-72, 0.53 with B-44. Surface identification and characterization of hydroxyapatite HA NPs/g-C3N4 hybrid nanocomposites embedded in B72/B44matrix were carried out using Scanning Electron Microscopy coupled with energy-dispersive x-ray spectroscopy (SEM–EDX).
Originality/value
This study provides important findings from the analytical procedures used to evaluate the consolidation materials used in this study. The findings are beneficial for the preservation of archaeological stucco. The investigation findings revealed that the most favorable outcomes were obtained from HA/g-C3N4 hybrid nanocomposites containing HA 0.5%, g-C3N4 1% and B-72 3%, as well as HA 0.5%, g-C3N4 1% and B-44 3%. Consequently, it is advised to use this nanocomposite to consolidate archaeological stucco, thus establishing a promising initial stride toward conserving archaeological stucco for future research endeavors. This study introduces a new nanocomposite material (HA NPs/G-C3N4) that can be used to protect and improve archaeological plaster. This is very important for preserving cultural heritage. The incorporation of nanotechnology improves the material’s physical and mechanical qualities. The research uses various characterization techniques (including TEM, XRD and FT-IR) to meticulously analyze the physicochemical properties of the nanocomposite material and assess its efficacy in practical applications through artificial aging experiments, offering novel insights and methodologies for future cultural relic preservation studies.
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Salwa H El-Sabbagh, Doaa S. Mahmoud, M. F. Zawrah, Nivin M. Ahmed and Magdy W. Sabaa
The purpose of this paper is to evaluate the efficiency of organobentonite (OB) as reinforcing filler in acrylonitrile-butadiene rubber (NBR). The composites were prepared using…
Abstract
Purpose
The purpose of this paper is to evaluate the efficiency of organobentonite (OB) as reinforcing filler in acrylonitrile-butadiene rubber (NBR). The composites were prepared using different loadings of OB and studying in details their properties. A series of OB was modified using surfactant N-cetyl-N, N, N-trimethyl ammonium bromide (CTAB) with concentrations 0.5, 1 and 2 cation exchange capacity (CEC) of bentonite.
Design/methodology/approach
The different bentonites were characterized using different analytical and spectro-photometric techniques, such as infra red, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy, while rubber vulcanizate rheological, morphological, swelling and thermal properties were examined using different standard instrumental testing and methods.
Findings
The study revealed that the modification of bentonite using CTAB showed significant enhancement on NBR properties, and the optimum filler loading was 12 phr for both 0.5CEC OB and 2CEC OB. These modified bentonites improved reinforcing properties to NBR vulcanizates. Also, results showed that composites exhibited remarkable improvements in tensile strength, elongation at break and hardness in the presence of modified bentonite and also an increase in thermal stability.
Research limitations/implications
Na-B cannot be applied in rubber matrix without modification because it is incompatible with it.
Practical implications
The modified bentonite is considered as efficient reinforcing filler which can replace other fillers because it has lower surface energy and improved intercalating behaviour in rubber matrix.
Originality/value
These papered bentonites are cheap with relatively high purity, which make rubber/clay composites emerge as new class of material and can be used in different fields other than rubber.
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To the extent that management accounting is based on neo‐classical economics, all decision‐making is assumed to be rational, aimed at utility or profit maximisation and all…
Abstract
To the extent that management accounting is based on neo‐classical economics, all decision‐making is assumed to be rational, aimed at utility or profit maximisation and all circumstances influencing decisions are accepted as stationary. The approach excludes all social, cultural or historical considerations and is based on perfect information that is freely available. Neo‐classical economics further assumes that minimum government intervention, which is regulated by competition, will result in maximum benefit for society as a whole. This paper aims to determine the extent to which management accounting theory has been based on these limiting assumptions and finds that emerging management accounting theory is increasingly based on alternative, more liberating foundations. This situation is in contrast to management accounting education in South Africa, which remains almost entirely based on neo‐classical economics.
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Naveed Ahmed, Umar Khan and Syed Tauseef Mohyud-din
The aim of this manuscript is to study the flow of a nanofluid through a porous channel under the influence of a transverse magnetic field. Permeability of the walls is…
Abstract
Purpose
The aim of this manuscript is to study the flow of a nanofluid through a porous channel under the influence of a transverse magnetic field. Permeability of the walls is considered to be different, which results in an asymmetric nature of the flow. The height of the channel is variable, and it dilates or squeezes at a uniform rate.
Design/methodology/approach
A numerical solution (Runge–Kutta–Fehlberg) has been obtained after reducing the governing equations to a system of nonlinear ordinary differential equations using some suitable similarity transforms, both in time and space.
Findings
An increase in absolute values of the permeability parameter results in an enhanced mass transfer rate at both the walls, while the rate of heat transfer also increases at the lower wall. Few graphs are also dedicated to see the behavior of Nusselt and Sherwood numbers following the variations in flow parameters.
Originality/value
A pictorial description of the flow and effects of emerging parameters on the temperature and nanoparticle concentration profiles is presented to analyze the flow behavior. It is established that the asymmetry of the channel affects the flow quite significantly.