Ahmad Jamal - Academia.edu (original) (raw)
Papers by Ahmad Jamal
To grasp progressive ideas and engage in teaching and research that contribute to the knowledge a... more To grasp progressive ideas and engage in teaching and research that contribute to the knowledge and sustainable development in the field of engineering by providing innovative solutions to identified technical problems and opportunities with highly rofessional attitude. p Degrees:
To grasp progressive ideas and engage in teaching and research that contribute to the knowledge a... more To grasp progressive ideas and engage in teaching and research that contribute to the knowledge and sustainable development in the field of engineering by providing innovative solutions to identified technical problems and opportunities with highly rofessional attitude. p Degrees:
A bstract The failure rate analysis of brake assemblies of a commercial airplane, i.e., Boeing 73... more A bstract The failure rate analysis of brake assemblies of a commercial airplane, i.e., Boeing 737, is analyzed using the Artificial Neural Network and Weibull regression models. One-layered feed-forward back-propagation algorithm for artificial neural network whereas three parameters model for Weibull are used for the analysis. Three years of data are used for model building and validation. The results show that the failure rate predicted by neural network is closer in agreement with the actual data than the failure rate predicted by the Weibull model. Results also indicate that neural network can be effectively integrated into aviation cost effective maintenance facility computerized material requirement planning system to forecast the number of brake assemblies needed for a given planning horizon.
7th AIAA ATIO Conf, 2nd CEIAT Int'l Conf on Innov and Integr in Aero Sciences,17th LTA Systems Tech Conf; followed by 2nd TEOS Forum, 2007
The failure rate analysis of brake assemblies of a commercial airplane, i.e., Boeing 737, is anal... more The failure rate analysis of brake assemblies of a commercial airplane, i.e., Boeing 737, is analyzed using the artificial neural network and Weibull regression models. One-layered feed-forward backpropagation algorithm for artificial neural network whereas three parameters model for Weibull are used for the analysis. Three years of data are used for model building and validation. The results show that the failure rate predicted by neural network is closer in agreement with the actual data than the failure rate predicted by the Weibull model. Results also indicate that neural network can be effectively integrated into an aviation maintenance facility computerized material requirement planning system to forecast the number of brake assemblies needed for a given planning horizon.
Quality and Reliability Engineering International, 2011
This paper presents an application of artificial neural network technique for predicting the fail... more This paper presents an application of artificial neural network technique for predicting the failure rate of Boeing 737 tires. For this purpose, an artificial neural network model utilizing the feed-forward backpropagation algorithm as a learning rule is developed. The inputs to the neural network are the independent variables and the output is the failure rate of the tires. Two years of data is used for failure rate prediction model and validation. Model validation, which reflects the suitability of the model for future predictions, is performed by comparing the predictions of the model with that of Weibull regression model. The results show that the failure rate predicted by the artificial neural network is closer in agreement with the actual data than the failure rate predicted by the Weibull model. The present work also identifies some of the common tire failures and presents representative results based on the established model for the most frequently occurring tire failure.
Journal of Engineering, 2022
Laminar natural convection-conduction heat transfer in vertically positioned annular channels wit... more Laminar natural convection-conduction heat transfer in vertically positioned annular channels with inherent eccentricity is investigated for optimum solid-fluid thermal conductivity ratio and optimum cylinder walls thicknesses allowing maximum induced fluid flow rate and heat transfer under varying geometry parameters, i.e., annulus eccentricity and radius ratio. A finite-difference technique is employed to solve the coupled momentum and energy equations for the cylindrical annulus walls and the annular fluid with Prandtl number 0.7. As part of the results, fluctuations in the induced fluid flow rate and heat transfer in the eccentric annular channel due to the conjugate effect, governed by the ratios of the solid and fluid thermal conductivities and thicknesses of outer and inner circular cylinder walls, are obtained for the boundary conditions of one wall heated isothermally and the other kept adiabatic. Commonly encountered ratios of the solid and fluid thermal conductivities and...
International Journal of Heat and Technology
The conjugate natural convection heat transfer in a partially heated square porous enclosure had ... more The conjugate natural convection heat transfer in a partially heated square porous enclosure had been studied numerically. The governing dimensionless equations are solved using COMSOL Multiphysics and Darcy model assumed to be used. The considering dimensionless parameters are modified Rayleigh number, finite wall thickness, thermal conductivity ratio and the heat source length. The results are presented in terms of streamlines, isotherms and local and average Nusselt number. The results indicate that; the heat transfer can be enhanced by increasing the modified Rayleigh number. When the heat source length increases, the local Nusselt number of fluid phase increases, while, a reverse behavior of the local Nusselt number along the heat source is found. As the Rayleigh number increase, the local Nusselt number for both fluid and solid phase increases, therefore, the heat transfer rate will be enhanced. On the other hand, when the thermal conductivity ratio increase, the local Nusselt number for the fluid phase increases, and the local Nusselt number along the heated wall decreases.
... Petroleum and Minerals. References 1. Al-Garni,AZ, Sahin,AZ, Al-Ghamdi,AS andAl-Kaabi, SA,&am... more ... Petroleum and Minerals. References 1. Al-Garni,AZ, Sahin,AZ, Al-Ghamdi,AS andAl-Kaabi, SA,"Reliability Analysis of Aeroplane Brakes", Quality and Reliability Engineering International, Vol.15,pp. 143-150, 1999. 2. Sheikh ...
The failure rate analysis of brake assemblies of a commercial airplane, i.e., Boeing 737, is anal... more The failure rate analysis of brake assemblies of a commercial airplane, i.e., Boeing 737, is analyzed using the artificial neural network and Weibull regression models. One-layered feed-forward back-propagation algorithm for artificial neural network whereas three parameters model for Weibull are used for the analysis. Three years of data are used for model building and validation. The results show that the failure rate predicted by neural network is closer in agreement with the actual data than the failure rate predicted by the Weibull model. Results also indicate that neural network can be effectively integrated into aviation cost effective maintenance facility computerized material requirement planning system to forecast the number of brake assemblies needed for a given planning horizon.
International Journal of Numerical Methods for Heat & Fluid Flow, 2007
Purpose-To explore the effect of the annulus geometrical parameters on the induced flow rate and ... more Purpose-To explore the effect of the annulus geometrical parameters on the induced flow rate and the heat transfer under the conjugate (combined conduction and free convection) thermal boundary conditions with one cylinder heated isothermally while the other cylinder is kept at the inlet fluid temperature. Design/methodology/approach-A finite-difference algorithm has been developed to solve the bipolar boundary-layer equations for the conjugate laminar free convection heat transfer in vertical eccentric annuli. Findings-Numerical results are presented for a fluid of Prandtl number, Pr ¼ 0.7 in eccentric annuli. The geometry parameters of NR 2 and E (the fluid-annulus radius ratio and the eccentricity, respectively) have considerable effects on the results. Practical implications-Applications of the obtained results can be of value in the heat-exchanger industry, in cooling of underground electric cables, and in cooling small vertical electric motors and generators. Originality/value-The paper presents results that are not available in the literature for the problem of conjugate laminar free convection in open-ended vertical eccentric annular channels. Geometry effects having been investigated by considering fluid annuli having radii ratios NR 2 ¼ 0.1 and 0.3, 0.5 and 0.7 and four values of the eccentricity E ¼ 0.1, 0.3, 0.5 and 0.7. Moreover, practical ranges of the solid-fluid conductivity ratio (KR) and the wall thicknesses that are commonly available in pipe standards have been investigated. Such results are very much needed for design purposes of heat transfer equipment.
Volume 4: Fluid-Structure Interaction, 2014
Transport in Porous Media, 2008
Entropy generation in the flow field subjected to a porous block situated in a vertical channel i... more Entropy generation in the flow field subjected to a porous block situated in a vertical channel is examined. The effects of channel inlet port height (vertical height between channel inlet port and the block center), porosity, and block aspect ratio on the entropy generation rate due to fluid friction and heat transfer in the fluid are examined. The governing equations of flow, heat transfer, and entropy are solved numerically using a control volume approach. Air is used as the flowing fluid in the channel. A uniform heat flux is considered in the block and natural convection is accommodated in the analysis. It is found that entropy generation rate due to fluid friction increases with increasing inlet port height, while this increase becomes gradual for entropy generation rate due to heat transfer for the inlet port height exceeding 0.03 m. The porosity lowers entropy generation rate due to fluid friction and heat transfer. The effect of block aspect ratio on entropy generation rate is notable; in which case, entropy generation rate increases for the block aspect ratio of 1:2.
Numerical Heat Transfer, Part A: Applications, 2004
The deformation of material and friction between the roll and deforming material contact region p... more The deformation of material and friction between the roll and deforming material contact region produce a large amount of heat. This heat energy is conducted toward the roll and the workpiece (strip). A well-designed cooling system is needed to control the material properties and grain structure of the rolled product. Therefore, complete knowledge of the temperature distribution in both the roll and strip is necessary to design an efficient cooling system to control the material properties. In this work, both the roll and strip have been modeled as a coupled heat transfer problem to predict the temperature distribution. Using a finite-volume approach, the governing differential equations as well as the boundary conditions are discretized, which are then solved numerically to predict the temperature distributions. The stability of the solution was examined by changing the grid sizes in the bite region; in addition, the numerical results are validated against published work in the literature for certain special operating conditions. The impact of roll speed and heat transfer coefficient on the distribution of heat flow in both the roll and workpiece are demonstrated through the temperature contour plots.
Numerical Heat Transfer, Part A: Applications, 2011
Combined conduction-free convection heat transfer in vertical eccentric annuli is numerically inv... more Combined conduction-free convection heat transfer in vertical eccentric annuli is numerically investigated using a finite-difference technique. The effects of geometrical parameters, such as eccentricity and radius ratio, on very practical parameters known as critical values of conductivity ratio above which and wall thickness below which the conjugate effect can be neglected, are presented. Solid-fluid thermal conductivity ratio is varied over a range covering practical cases with commonly encountered wall thicknesses. The obtained results can be of value in many industrial applications. The numerical results show that conjugate effects can be increased or decreased by controlling the geometrical parameters.
Journal of Aircraft, 2007
This paper presents methods for modeling the failure of air-conditioning/cooling packs for a part... more This paper presents methods for modeling the failure of air-conditioning/cooling packs for a particular type of aircraft with field data. In many regards, field data are highly desirable for more accurate failure prediction by aircraft operators, because the data implicitly account for all actual usage and environmental stresses. It is not always possible to accurately anticipate or simulate these stresses in a laboratory or even in a field test. Field data, in a larger extent, are also important to the manufacturer, because the data identify product deficiencies and areas of improvement. In this study, the failure of the aircraft air-conditioning/cooling pack under a customer-use environment is first modeled at the component level by using the Weibull distribution and its extensions. These include the two-parameter Weibull model, three-parameter Weibull model, mixture model, and phased bi-Weibull model. The number of failures over time is estimated by a renewal process. The failure of the air-conditioning/cooling pack at the system level is then modeled by using the power law process model. The failure trend is tested by the Laplace test. The results give an insight into the reliability and quality of the air-conditioning/cooling pack under actual operating conditions. The models presented here can be used by aircraft operators for assessing system and component failures and customizing the maintenance programs recommended by the manufacturer.
Journal of Aircraft, 2006
An artificial neural-network model for predicting the failure rate of De Havilland Dash-8 airplan... more An artificial neural-network model for predicting the failure rate of De Havilland Dash-8 airplane tires utilizing the two-layered feedforward back-propagation algorithm as a learning rule is developed. The inputs to the neural network are independent variables, and the output is the failure rate of the tires. Six years of data are used for model building and validation. Model validation, which reflects the suitability of the model for future prediction, is performed by comparing the predictions of the model with that of the Weibull regression model. The results show that the failure rate predicted by the artificial neural network more closely agrees with the actual data than the failure rate predicted by the Weibull model.
International Journal for Computational Methods in Engineering Science and Mechanics, 2005
International Journal for Computational Methods in Engineering Science and Mechanics, 6:235250, ... more International Journal for Computational Methods in Engineering Science and Mechanics, 6:235250, 2005 Copyright c Taylor & Francis Inc. ISSN: 15502287 print / 15502295 online DOI: 10.1080/155022891009288 ... Conjugate Effects on Steady Laminar Natural ...
Engineering Applications of Artificial Intelligence, 2006
An artificial neural network (ANN) model for predicting the failure rate of De Havilland Dash-8 a... more An artificial neural network (ANN) model for predicting the failure rate of De Havilland Dash-8 airplane tires utilizing the two-layered feed-forward back-propagation algorithm as a learning rule is developed. The inputs to the neural network are independent variables ...
To grasp progressive ideas and engage in teaching and research that contribute to the knowledge a... more To grasp progressive ideas and engage in teaching and research that contribute to the knowledge and sustainable development in the field of engineering by providing innovative solutions to identified technical problems and opportunities with highly rofessional attitude. p Degrees:
To grasp progressive ideas and engage in teaching and research that contribute to the knowledge a... more To grasp progressive ideas and engage in teaching and research that contribute to the knowledge and sustainable development in the field of engineering by providing innovative solutions to identified technical problems and opportunities with highly rofessional attitude. p Degrees:
A bstract The failure rate analysis of brake assemblies of a commercial airplane, i.e., Boeing 73... more A bstract The failure rate analysis of brake assemblies of a commercial airplane, i.e., Boeing 737, is analyzed using the Artificial Neural Network and Weibull regression models. One-layered feed-forward back-propagation algorithm for artificial neural network whereas three parameters model for Weibull are used for the analysis. Three years of data are used for model building and validation. The results show that the failure rate predicted by neural network is closer in agreement with the actual data than the failure rate predicted by the Weibull model. Results also indicate that neural network can be effectively integrated into aviation cost effective maintenance facility computerized material requirement planning system to forecast the number of brake assemblies needed for a given planning horizon.
7th AIAA ATIO Conf, 2nd CEIAT Int'l Conf on Innov and Integr in Aero Sciences,17th LTA Systems Tech Conf; followed by 2nd TEOS Forum, 2007
The failure rate analysis of brake assemblies of a commercial airplane, i.e., Boeing 737, is anal... more The failure rate analysis of brake assemblies of a commercial airplane, i.e., Boeing 737, is analyzed using the artificial neural network and Weibull regression models. One-layered feed-forward backpropagation algorithm for artificial neural network whereas three parameters model for Weibull are used for the analysis. Three years of data are used for model building and validation. The results show that the failure rate predicted by neural network is closer in agreement with the actual data than the failure rate predicted by the Weibull model. Results also indicate that neural network can be effectively integrated into an aviation maintenance facility computerized material requirement planning system to forecast the number of brake assemblies needed for a given planning horizon.
Quality and Reliability Engineering International, 2011
This paper presents an application of artificial neural network technique for predicting the fail... more This paper presents an application of artificial neural network technique for predicting the failure rate of Boeing 737 tires. For this purpose, an artificial neural network model utilizing the feed-forward backpropagation algorithm as a learning rule is developed. The inputs to the neural network are the independent variables and the output is the failure rate of the tires. Two years of data is used for failure rate prediction model and validation. Model validation, which reflects the suitability of the model for future predictions, is performed by comparing the predictions of the model with that of Weibull regression model. The results show that the failure rate predicted by the artificial neural network is closer in agreement with the actual data than the failure rate predicted by the Weibull model. The present work also identifies some of the common tire failures and presents representative results based on the established model for the most frequently occurring tire failure.
Journal of Engineering, 2022
Laminar natural convection-conduction heat transfer in vertically positioned annular channels wit... more Laminar natural convection-conduction heat transfer in vertically positioned annular channels with inherent eccentricity is investigated for optimum solid-fluid thermal conductivity ratio and optimum cylinder walls thicknesses allowing maximum induced fluid flow rate and heat transfer under varying geometry parameters, i.e., annulus eccentricity and radius ratio. A finite-difference technique is employed to solve the coupled momentum and energy equations for the cylindrical annulus walls and the annular fluid with Prandtl number 0.7. As part of the results, fluctuations in the induced fluid flow rate and heat transfer in the eccentric annular channel due to the conjugate effect, governed by the ratios of the solid and fluid thermal conductivities and thicknesses of outer and inner circular cylinder walls, are obtained for the boundary conditions of one wall heated isothermally and the other kept adiabatic. Commonly encountered ratios of the solid and fluid thermal conductivities and...
International Journal of Heat and Technology
The conjugate natural convection heat transfer in a partially heated square porous enclosure had ... more The conjugate natural convection heat transfer in a partially heated square porous enclosure had been studied numerically. The governing dimensionless equations are solved using COMSOL Multiphysics and Darcy model assumed to be used. The considering dimensionless parameters are modified Rayleigh number, finite wall thickness, thermal conductivity ratio and the heat source length. The results are presented in terms of streamlines, isotherms and local and average Nusselt number. The results indicate that; the heat transfer can be enhanced by increasing the modified Rayleigh number. When the heat source length increases, the local Nusselt number of fluid phase increases, while, a reverse behavior of the local Nusselt number along the heat source is found. As the Rayleigh number increase, the local Nusselt number for both fluid and solid phase increases, therefore, the heat transfer rate will be enhanced. On the other hand, when the thermal conductivity ratio increase, the local Nusselt number for the fluid phase increases, and the local Nusselt number along the heated wall decreases.
... Petroleum and Minerals. References 1. Al-Garni,AZ, Sahin,AZ, Al-Ghamdi,AS andAl-Kaabi, SA,&am... more ... Petroleum and Minerals. References 1. Al-Garni,AZ, Sahin,AZ, Al-Ghamdi,AS andAl-Kaabi, SA,"Reliability Analysis of Aeroplane Brakes", Quality and Reliability Engineering International, Vol.15,pp. 143-150, 1999. 2. Sheikh ...
The failure rate analysis of brake assemblies of a commercial airplane, i.e., Boeing 737, is anal... more The failure rate analysis of brake assemblies of a commercial airplane, i.e., Boeing 737, is analyzed using the artificial neural network and Weibull regression models. One-layered feed-forward back-propagation algorithm for artificial neural network whereas three parameters model for Weibull are used for the analysis. Three years of data are used for model building and validation. The results show that the failure rate predicted by neural network is closer in agreement with the actual data than the failure rate predicted by the Weibull model. Results also indicate that neural network can be effectively integrated into aviation cost effective maintenance facility computerized material requirement planning system to forecast the number of brake assemblies needed for a given planning horizon.
International Journal of Numerical Methods for Heat & Fluid Flow, 2007
Purpose-To explore the effect of the annulus geometrical parameters on the induced flow rate and ... more Purpose-To explore the effect of the annulus geometrical parameters on the induced flow rate and the heat transfer under the conjugate (combined conduction and free convection) thermal boundary conditions with one cylinder heated isothermally while the other cylinder is kept at the inlet fluid temperature. Design/methodology/approach-A finite-difference algorithm has been developed to solve the bipolar boundary-layer equations for the conjugate laminar free convection heat transfer in vertical eccentric annuli. Findings-Numerical results are presented for a fluid of Prandtl number, Pr ¼ 0.7 in eccentric annuli. The geometry parameters of NR 2 and E (the fluid-annulus radius ratio and the eccentricity, respectively) have considerable effects on the results. Practical implications-Applications of the obtained results can be of value in the heat-exchanger industry, in cooling of underground electric cables, and in cooling small vertical electric motors and generators. Originality/value-The paper presents results that are not available in the literature for the problem of conjugate laminar free convection in open-ended vertical eccentric annular channels. Geometry effects having been investigated by considering fluid annuli having radii ratios NR 2 ¼ 0.1 and 0.3, 0.5 and 0.7 and four values of the eccentricity E ¼ 0.1, 0.3, 0.5 and 0.7. Moreover, practical ranges of the solid-fluid conductivity ratio (KR) and the wall thicknesses that are commonly available in pipe standards have been investigated. Such results are very much needed for design purposes of heat transfer equipment.
Volume 4: Fluid-Structure Interaction, 2014
Transport in Porous Media, 2008
Entropy generation in the flow field subjected to a porous block situated in a vertical channel i... more Entropy generation in the flow field subjected to a porous block situated in a vertical channel is examined. The effects of channel inlet port height (vertical height between channel inlet port and the block center), porosity, and block aspect ratio on the entropy generation rate due to fluid friction and heat transfer in the fluid are examined. The governing equations of flow, heat transfer, and entropy are solved numerically using a control volume approach. Air is used as the flowing fluid in the channel. A uniform heat flux is considered in the block and natural convection is accommodated in the analysis. It is found that entropy generation rate due to fluid friction increases with increasing inlet port height, while this increase becomes gradual for entropy generation rate due to heat transfer for the inlet port height exceeding 0.03 m. The porosity lowers entropy generation rate due to fluid friction and heat transfer. The effect of block aspect ratio on entropy generation rate is notable; in which case, entropy generation rate increases for the block aspect ratio of 1:2.
Numerical Heat Transfer, Part A: Applications, 2004
The deformation of material and friction between the roll and deforming material contact region p... more The deformation of material and friction between the roll and deforming material contact region produce a large amount of heat. This heat energy is conducted toward the roll and the workpiece (strip). A well-designed cooling system is needed to control the material properties and grain structure of the rolled product. Therefore, complete knowledge of the temperature distribution in both the roll and strip is necessary to design an efficient cooling system to control the material properties. In this work, both the roll and strip have been modeled as a coupled heat transfer problem to predict the temperature distribution. Using a finite-volume approach, the governing differential equations as well as the boundary conditions are discretized, which are then solved numerically to predict the temperature distributions. The stability of the solution was examined by changing the grid sizes in the bite region; in addition, the numerical results are validated against published work in the literature for certain special operating conditions. The impact of roll speed and heat transfer coefficient on the distribution of heat flow in both the roll and workpiece are demonstrated through the temperature contour plots.
Numerical Heat Transfer, Part A: Applications, 2011
Combined conduction-free convection heat transfer in vertical eccentric annuli is numerically inv... more Combined conduction-free convection heat transfer in vertical eccentric annuli is numerically investigated using a finite-difference technique. The effects of geometrical parameters, such as eccentricity and radius ratio, on very practical parameters known as critical values of conductivity ratio above which and wall thickness below which the conjugate effect can be neglected, are presented. Solid-fluid thermal conductivity ratio is varied over a range covering practical cases with commonly encountered wall thicknesses. The obtained results can be of value in many industrial applications. The numerical results show that conjugate effects can be increased or decreased by controlling the geometrical parameters.
Journal of Aircraft, 2007
This paper presents methods for modeling the failure of air-conditioning/cooling packs for a part... more This paper presents methods for modeling the failure of air-conditioning/cooling packs for a particular type of aircraft with field data. In many regards, field data are highly desirable for more accurate failure prediction by aircraft operators, because the data implicitly account for all actual usage and environmental stresses. It is not always possible to accurately anticipate or simulate these stresses in a laboratory or even in a field test. Field data, in a larger extent, are also important to the manufacturer, because the data identify product deficiencies and areas of improvement. In this study, the failure of the aircraft air-conditioning/cooling pack under a customer-use environment is first modeled at the component level by using the Weibull distribution and its extensions. These include the two-parameter Weibull model, three-parameter Weibull model, mixture model, and phased bi-Weibull model. The number of failures over time is estimated by a renewal process. The failure of the air-conditioning/cooling pack at the system level is then modeled by using the power law process model. The failure trend is tested by the Laplace test. The results give an insight into the reliability and quality of the air-conditioning/cooling pack under actual operating conditions. The models presented here can be used by aircraft operators for assessing system and component failures and customizing the maintenance programs recommended by the manufacturer.
Journal of Aircraft, 2006
An artificial neural-network model for predicting the failure rate of De Havilland Dash-8 airplan... more An artificial neural-network model for predicting the failure rate of De Havilland Dash-8 airplane tires utilizing the two-layered feedforward back-propagation algorithm as a learning rule is developed. The inputs to the neural network are independent variables, and the output is the failure rate of the tires. Six years of data are used for model building and validation. Model validation, which reflects the suitability of the model for future prediction, is performed by comparing the predictions of the model with that of the Weibull regression model. The results show that the failure rate predicted by the artificial neural network more closely agrees with the actual data than the failure rate predicted by the Weibull model.
International Journal for Computational Methods in Engineering Science and Mechanics, 2005
International Journal for Computational Methods in Engineering Science and Mechanics, 6:235250, ... more International Journal for Computational Methods in Engineering Science and Mechanics, 6:235250, 2005 Copyright c Taylor & Francis Inc. ISSN: 15502287 print / 15502295 online DOI: 10.1080/155022891009288 ... Conjugate Effects on Steady Laminar Natural ...
Engineering Applications of Artificial Intelligence, 2006
An artificial neural network (ANN) model for predicting the failure rate of De Havilland Dash-8 a... more An artificial neural network (ANN) model for predicting the failure rate of De Havilland Dash-8 airplane tires utilizing the two-layered feed-forward back-propagation algorithm as a learning rule is developed. The inputs to the neural network are independent variables ...