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97 results on '"Diab, Ahmed M."'

12. Slant shear bond strength between self compacting concrete and old concrete

Author

Diab, Ahmed M., Elmoaty, Abd Elmoaty M. Abd, and Eldin, Mohamed R. Tag

Subjects
Concrete -- Analysis -- Mechanical properties, Business, Construction and materials industries
Abstract

ABSTRACT This experimental investigation aims to study the bond strength between old and new self-compacting concrete (SCC). The first part presents the factors affecting slant shear bond strength between old [...]

Published
2017
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16. Impact of organic carbon on hardened properties and durability of limestone cement concrete

Author

Diab, Ahmed M., Mohamed, Ismail A., and Aliabdo, Ali A.

Subjects
Portland cement -- Electric properties -- Analysis, Corrosion and anti-corrosives -- Analysis, Polarization (Electricity) -- Analysis, Business, Construction and materials industries
Abstract

ABSTRACT In this paper, the effect of organic carbon in ground limestone on the properties and behavior of Portland limestone cement (PLC) concrete in normal and aggressive medium was studied. [...]

Published
2016
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26. An Overview of the Agricultural Extension System in Egypt: The History, Structure, Modes of Operation and the Future Directions

Author

Diab, Ahmed M., Yacoub, Mohamed, and AbdelAal, Mohamed H.

Subjects
logical frame analysis, review, agricultural extension, Egypt, Teaching/Communication/Extension/Profession, SWOT
Abstract

The main purpose of the current manuscript is to review the agricultural extension system in Egypt. The information gleaned in this article could be useful for policymakers, extension administrators, and extension researchers to identify ways for improving educational services of devising training programs for audience and agents, approaches of farmers' participation, and schemes of policy development. More specifically the objectives of this study are to review the Egyptian agricultural extension system in terms of the: 1) the history of the Egyptian agricultural extension system, 2) the organizational structure of the Egyptian extension system, 3) types of agricultural extension and program delivery mechanisms in Egypt, 4) current situation of the Egyptian agricultural extension system, and 5) the possible future direction for the Egyptian agricultural extension system. A comprehensive review of gray literature was conducted to identify characteristics of the agricultural extension system in Egypt, relevant documents used including, foundation legislation, review and analysis of literature of international organizations as well as peer reviewed journal articles. The extension history, structure, and modes of operation were discussed, and the future directions were concluded.

Published
2020
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31. An Overmodulation Algorithm With Neutral-Point Voltage Balancing for Three-Level Converters in High-Speed Aerospace Drives.

Author

Guo, Feng, Yang, Tao, Diab, Ahmed M., Yeoh, Seang Shen, Li, Chen, Bozhko, Serhiy, and Wheeler, Patrick

Subjects
VOLTAGE, VOLTAGE control, VECTOR spaces, ALGORITHMS, ELECTRIC potential, AC DC transformers, ELECTRIC generators
Abstract

In this article, a virtual space vector based overmodulation algorithm is presented for three-level neutral-point (NP) clamped converters in high-speed aerospace motor drives. With the proposed inscribed polygonal-boundary compression technique, the output voltage capability is enhanced under a lower crossover angle and compression coefficient. As a result, it brings an opportunity for the operation of the studied aircraft electric starter/generator (ESG) systems easily extending from the linear modulation range into the overmodulation region. Furthermore, an active capacitor voltage balancing control method is investigated to recover NP potential imbalance in the case of high modulation index and low power factor operating conditions. To simplify the digital implementation of the algorithm, a fast calculation approach is adopted in this work. The modulation performance of the proposed strategy is verified by both simulation and experimental results with a 45 kW, 32 k r/min ESG prototype system. [ABSTRACT FROM AUTHOR]

Published
2022
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35. Mobile-based advisory services for sustainable agriculture: Assessing farmers' information behavior.

Author

Kassem, Hazem S., Alotaibi, Bader Alhafi, Ghoneim, Yomna A., and Diab, Ahmed M.

Subjects
INFORMATION-seeking behavior, SUSTAINABLE agriculture, FARM size, FARMERS, SEED treatment, SMALL farms
Abstract

Mobile-based advisory services have significant benefits, including access to agricultural information, knowledge sharing, meteorological information, marketing-related information, and financial services for smallholder farmers. This study aimed to assess farmers' information behavior regarding mobile-based advisory services and how farmers with different characteristics and attitudes access and adopt information. Data were collected from 382 farmers in Dakhalia governorate, Egypt. The most frequently received information was related to best agricultural practices, weather forecasts, seed varieties and treatment, and water management. Cluster analysis revealed that 47% of the farmers had low information behavior. Seventy-one of the respondents had a favorable attitude toward information retrieval from mobile agricultural services. The information behavior groups of the farmers significantly differed in education, farm size, diversity of agricultural production, and attitude regarding trust and quality of the information provided. Information behavior among farmers has useful implications for policymakers in supporting the long-term benefits of mobile-based advisory services. [ABSTRACT FROM AUTHOR]

Published
2021
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36. How Does Organizational Climate Contribute to Job Satisfaction and Commitment of Agricultural Extension Personnel in New Valley Governorate, Egypt?

Author

Diab, Ahmed M., Diab, Hend M., and Emam, Dina H.

Subjects
*JOB satisfaction, *INSTITUTIONAL environment, *AGRICULTURAL extension work, *ORGANIZATIONAL commitment, *NULL hypothesis, *AGRICULTURAL forecasts
Abstract

This research aimed to 1) explore the organizational climate of the agricultural extension in New Valley Governorate, 2) explore the status quo of job satisfaction and commitment of extension personnel in the New Valley Governorate, and 3) investigate the impact of agricultural extension organizational climate on job satisfaction and commitment of extension personnel. Data were collected using the questionnaire form during January to February 2021, from a sample of 25 Extension personnel representing 37.3% of their total number in New Valley Governorate (67 Personnel). Frequencies, mean, standard deviation and stepwise regression analysis were used for data presentation and analysis. Findings revealed that the respondents’ perceptions overall mean score of the organizational climate reached 68.26% of the total score, their job satisfaction is 73.6% of the total score, and their organizational commitment reached 68.4% of the total score. Findings also show that the variable of “Efficiency” contribute to the interpretation of 19.6% and 57.7% of variance of the Job Satisfaction and Employees' Commitment, respectively. Other variable influenced the Job Satisfaction is “Outward Focus” which contributed 37% of the explanation of the variance of the overall Job Satisfaction. Results also revealed that the variable of " Clarity of Organizational Goals" is contributed to the interpretation of 10.7% of variance of the Job Satisfaction. Based on the previous results the null hypotheses numbers 10, 12, 13, and 31 could be rejected, while the remaining null hypotheses couldn’t be rejected. [ABSTRACT FROM AUTHOR]

Published
2021
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44. Corrosion behaviour of reinforced steel in concrete with ground limestone partial cement replacement.

Author

Mohamed, Ismail A., Aliabdo, Ali A., and Diab, Ahmed M.

Subjects
CORROSION & anti-corrosives, CONCRETE construction, CEMENT research, X-ray diffraction, STEEL bars
Abstract

Corrosion of steel bars embedded in concrete made of Portland cement replaced partially with ground limestone is studied. Three variables are considered: replacement ratios with ground limestone (0, 10, 15, 20 and 25% of cement by weight), level of cement content (300, 350 and 400 kg/m) and fineness of ground limestone (345, 530 and 720 m/kg). Reinforced concrete specimens are immersed in a 5% sodium chloride solution by weight up to 9 months. The corrosion rate is measured by potentiodynamic polarisation technique. To explain the corrosion behaviour of steel bar embedded in Portland limestone cement concrete, samples are prepared from the same concrete mixes and tested mechanically and physically. X-ray diffraction and thermogravimetric analyses of limestone cement pastes with similar replacement levels are also conducted. The corrosion rate of steel bars embedded in concrete containing ground limestone (530 m/kg or more) is found to decrease with increase of cement replacement ratio up to 25% by weight. The corrosion behaviour of steel bars and the resistivity characteristics of Portland limestone cement concrete are also found essentially to depend on the cement content of the concrete. The corrosion behaviour of steel bars in Portland limestone cement concrete, as well as the compressive strength of the concrete, is found to be strongly associated with the fineness of limestone relative to the fineness of cement. [ABSTRACT FROM AUTHOR]

Published
2015
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45. Investigating electrical drive performance employing model predictive control and active disturbance rejection control algorithms

Author

Aboelhassan, Ahmed, Diab, Ahmed M., Galea, Michael, Bozhko, Serhiy, Aboelhassan, Ahmed, Diab, Ahmed M., Galea, Michael, and Bozhko, Serhiy

Abstract

Many issues can degrade the electrical drive performance such as cross-coupling, time delay, external disturbances, and parameter variation. The Synchronous Reference Frame (SRF) PI Current Controller (CC) is the most popular control scheme for the motor drive current control due to its simplicity. However, the PI controller does not have an optimal dynamic response due to the reasonably low transient response of the integral parts. Furthermore, the tuning of the PI controller depends heavily on the machine’s parameters. Recently, alternative control schemes such as Model Predictive Control (MPC) and Active Disturbance Rejection Control (ADRC) are studied due to their dynamic performance and disturbance rejection capability, respectively. This paper presents a comparative study between the conventional PI, ADRC, and MPC control schemes applied for Permanent Magnet Synchronous Motor (PMSM) taking into consideration the operational issues of electrical drives.

46. Stable and robust design of active disturbance-rejection current controller for permanent magnet machines in transportation systems

Author

Diab, Ahmed M., Bozhko, Serhiy, Galea, Michael, Gerada, Christopher, Diab, Ahmed M., Bozhko, Serhiy, Galea, Michael, and Gerada, Christopher

Abstract

Active disturbance-rejection control (ADRC) as a current control (CC) method for ac drive systems has been recently shown to have significant strengths. Its robustness to system uncertainties and its high disturbance-rejection capability render it an attractive control scheme for various mobile applications. Until now, however, all the known tuning methods available in literature are based on a number of assumptions that may lead to the degraded drive performance and even to the loss of stability. This article, thus, provides a rigorous analysis and proposes a new CC design method based on the ADRC technique. The design derives a generic closed-loop transfer function considering system delays and the dynamics of the extended state observer. Based on this analysis, a tuning method able to guarantee a set performance to avoid unstable operation is thus proposed. The effects of model uncertainties on the current loop system stability and robustness are also analyzed and reported. A tuning criterion to enhance system robustness and to improve its dynamic performance is developed and validated experimentally on a case study system.

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47. Stable and robust design of active disturbance-rejection current controller for permanent magnet machines in transportation systems

Author

Diab, Ahmed M., Bozhko, Serhiy, Galea, Michael, Gerada, Christopher, Diab, Ahmed M., Bozhko, Serhiy, Galea, Michael, and Gerada, Christopher

Abstract

Active disturbance-rejection control (ADRC) as a current control (CC) method for ac drive systems has been recently shown to have significant strengths. Its robustness to system uncertainties and its high disturbance-rejection capability render it an attractive control scheme for various mobile applications. Until now, however, all the known tuning methods available in literature are based on a number of assumptions that may lead to the degraded drive performance and even to the loss of stability. This article, thus, provides a rigorous analysis and proposes a new CC design method based on the ADRC technique. The design derives a generic closed-loop transfer function considering system delays and the dynamics of the extended state observer. Based on this analysis, a tuning method able to guarantee a set performance to avoid unstable operation is thus proposed. The effects of model uncertainties on the current loop system stability and robustness are also analyzed and reported. A tuning criterion to enhance system robustness and to improve its dynamic performance is developed and validated experimentally on a case study system.

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48. Investigating electrical drive performance employing model predictive control and active disturbance rejection control algorithms

Author

Aboelhassan, Ahmed, Diab, Ahmed M., Galea, Michael, Bozhko, Serhiy, Aboelhassan, Ahmed, Diab, Ahmed M., Galea, Michael, and Bozhko, Serhiy

Abstract

Many issues can degrade the electrical drive performance such as cross-coupling, time delay, external disturbances, and parameter variation. The Synchronous Reference Frame (SRF) PI Current Controller (CC) is the most popular control scheme for the motor drive current control due to its simplicity. However, the PI controller does not have an optimal dynamic response due to the reasonably low transient response of the integral parts. Furthermore, the tuning of the PI controller depends heavily on the machine’s parameters. Recently, alternative control schemes such as Model Predictive Control (MPC) and Active Disturbance Rejection Control (ADRC) are studied due to their dynamic performance and disturbance rejection capability, respectively. This paper presents a comparative study between the conventional PI, ADRC, and MPC control schemes applied for Permanent Magnet Synchronous Motor (PMSM) taking into consideration the operational issues of electrical drives.

49. Stable and robust design of active disturbance-rejection current controller for permanent magnet machines in transportation systems

Author

Diab, Ahmed M., Bozhko, Serhiy, Galea, Michael, Gerada, Christopher, Diab, Ahmed M., Bozhko, Serhiy, Galea, Michael, and Gerada, Christopher

Abstract

Active disturbance-rejection control (ADRC) as a current control (CC) method for ac drive systems has been recently shown to have significant strengths. Its robustness to system uncertainties and its high disturbance-rejection capability render it an attractive control scheme for various mobile applications. Until now, however, all the known tuning methods available in literature are based on a number of assumptions that may lead to the degraded drive performance and even to the loss of stability. This article, thus, provides a rigorous analysis and proposes a new CC design method based on the ADRC technique. The design derives a generic closed-loop transfer function considering system delays and the dynamics of the extended state observer. Based on this analysis, a tuning method able to guarantee a set performance to avoid unstable operation is thus proposed. The effects of model uncertainties on the current loop system stability and robustness are also analyzed and reported. A tuning criterion to enhance system robustness and to improve its dynamic performance is developed and validated experimentally on a case study system.

Full Text
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50. Investigating electrical drive performance employing model predictive control and active disturbance rejection control algorithms

Author

Aboelhassan, Ahmed, Diab, Ahmed M., Galea, Michael, Bozhko, Serhiy, Aboelhassan, Ahmed, Diab, Ahmed M., Galea, Michael, and Bozhko, Serhiy

Abstract

Many issues can degrade the electrical drive performance such as cross-coupling, time delay, external disturbances, and parameter variation. The Synchronous Reference Frame (SRF) PI Current Controller (CC) is the most popular control scheme for the motor drive current control due to its simplicity. However, the PI controller does not have an optimal dynamic response due to the reasonably low transient response of the integral parts. Furthermore, the tuning of the PI controller depends heavily on the machine’s parameters. Recently, alternative control schemes such as Model Predictive Control (MPC) and Active Disturbance Rejection Control (ADRC) are studied due to their dynamic performance and disturbance rejection capability, respectively. This paper presents a comparative study between the conventional PI, ADRC, and MPC control schemes applied for Permanent Magnet Synchronous Motor (PMSM) taking into consideration the operational issues of electrical drives.

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