Optimal control and design of composite laminated piezoelectric plates

ALhadi E. ALamir 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.15 No.5

The present paper is concerned with the optimal control and/or design of symmetric and antisymmetric composite laminate with two piezoelectric layers bonded to the opposite surfaces of the laminate, and placed symmetrically with respect to the middle plane. For the optimal control problem, Liapunov-Bellman theory is used to minimize the dynamic response of the laminate. The dynamic response of the laminate comprises a weight sum of the control objective (the total vibrational energy) and a penalty functional including the control force. Simultaneously with the active control, thicknesses and the orientation angles of layers are taken as design variables to achieve optimum design. The formulation is based on various plate theories for various boundary conditions. Explicit solutions for the control function and controlled deflections are obtained in forms of double series. Numerical results are given to demonstrate the effectiveness of the proposed control and design mechanism, and to investigate the effects of various laminate parameters on the control and design process.

Electrospun Nanofibers: Preparation, Characterization and Atmospheric Fog Capturing Capabilities

M. A. Alamir,I. M. Alarifi,W. A. Khan,W. S. Khan,R. Asmatulu 한국섬유공학회 2019 Fibers and polymers Vol.20 No.10

This study was aimed at enhancing the capability of electrospun nanofiber mats to convert atmospheric fog intofresh water effectively. The demand for clean water has been increasing worldwide, and this problem can be addressedeconomically by utilizing new technologies. It is known that atmospheric fresh water found on the earth is about 0.03 % ofthe total global fresh water, which is more than enough to meet the demand for fresh water in many locations. Althoughdesalination may produce a significant quantity of fresh water, it is a fairly costly, energy-intensive, and time-consumingprocess. In this research, the electrospinning method was used to fabricate superhydrophilic polyacrylonitrile (PAN) andpolyvinyl chloride (PVC) nanofiber mats incorporated with hydrophilic polymers of polyvinylpyrrolidone (PVP),polyethylene glycol (PEG), and chitosan at various direct current (DC) voltages, pump speeds, and tip-to-collector distances,in order to evaluate their capability of capturing fresh water from atmospheric fog. Fourier transform infrared (FTIR) andRaman spectroscopy were used to characterize the chemical structures of the nanofibers, while scanning electron microscopy(SEM) and water contact angle measurement methods were used to determine the morphology and surface hydrophobicity,respectively, of the produced nanofibers. At higher concentrations of PVP, PEG, and chitosan (e.g., 16 and 32 wt%), most ofthe electrospun nanofibers were superhydrophilic, with water contact angle values less than 5 o in 0.5 seconds. Humidifierand humidity test chamber results indicated that superhydrophilic nanofibers could absorb up to 69 % of their weight in ashorter period of time. This scalable process can be extended to capturing a larger quantity of fresh water from theatmosphere.

Prioritizing Service Supply-Chain Performance Measures Using Multi-Criteria Decision-Making Methodologies

Haidar ABBAS,Alamir Al ALAWI,Khadija Al MAKTOUMI 한국유통과학회 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.11

This study focuses on identifying and prioritizing the broader performance measures for the service supply chains by taking the case of Majan Electricity Company, Sohar, in the Sultanate of Oman. For an examination of the uniformity of ultimate objectives and the priorities therein, two strata of respondents with a total of fourteen respondents were approached for their valuable insights. Suitable structured instruments were personally administered to elicit the insightful and worthy responses. The two multi-criteria decision-making techniques, namely, the Fuzzy Analytical Hierarchy Process and the Best-Worst Method were used to reach a meaningful prioritization of the identified and refined broader performance measurement dimensions. The results show that there exists a minor gap between the two respondents’ groups in terms of their prioritizations. The major finding points to the difference in terms of the topmost priorities as revealed by the two set of respondents. For one group of respondents, the customer satisfaction matters the most, whereas for the other group, it is the overall profitability that matters the most. This gap against the utopian state assists in concluding that there is a requirement to reorient the employees so as to have a shared and common understanding of the organizational priorities.

Fixed-frequency phase-shift modulated PV-MPPT for LLC resonant converters

Abdel-Rahim, Omar,Alamir, Nehmido,Orabi, Mohamed,Ismeil, Mohamed The Korean Institute of Power Electronics 2020 JOURNAL OF POWER ELECTRONICS Vol.20 No.1

The micro-inverter has attracted a great deal of attention in PV systems since it offers a superior solution for the shading problem in wide spreading of AC module technology, where each PV module has its own power conditioner. The micro-inverter is implemented from two-stages: DC-DC conversion and DC-AC conversion. This paper focuses on the first-stage of the micro-inverter including its high-gain and maximum power point tracking (MPPT). To achieve these features, an efficient MPPT algorithm is proposed for the LLC resonant-converter. Resonant converters are very promising topologies, due to their inherent features such as high-efficiency and very high-switching-frequency operation. Consequently, they have a small footprint and low switching losses due to zero-voltage-switching (ZVS) operation. To include resonant converters in PV applications, MPPT control is applied. Due to the non-symmetrical operation nature of resonant converters and pulse width modulated converters, the traditional MPPT techniques found in the literature are not suitable for direct application to the resonant converters. They need to be well-tuned before application to a resonant converter. To ease the usage of resonant converters in PV applications, this paper develops a novel phase-shift fixed-frequency MPPT algorithm that is compatible with the LLC resonant converter. It also reduces the EMI when compared to variable-frequency modulation due to the use of ZVS and a fixed frequency. The proposed MPPT technique achieves good performance, high steady-state efficiency and good dynamic response. The complete design procedure and analysis for the proposed MPPT phase-shift algorithm are presented in this paper. Finally, the presented system is validated based on PSIM simulations and hardware implementation on a 300-W prototype.

Oral Squamous Cell Carcinoma and Associated Risk Factors in Jazan, Saudi Arabia: A Hospital Based Case Control Study

Quadri, Mir Faeq Ali,Alharbi, Fahd,Bajonaid, Amal Mansoor S,Moafa, Ibtisam Hussain Y,Sharwani, Abubakker Al,Alamir, Abdulwahab Hussain A Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.10

Background: Oral cancer is the third most common malignancy in Saudi Arabia, the highest incidence of which is reported from Jazan province. The objective of this study was to evaluate the association of various locally used substances, especially shamma, with oral cancer in the Jazan region of Saudi Arabia. Materials and Methods: A hospital-based case-control study was designed and patient records were scanned for histologically confirmed oral cancer cases. Forty eight patients who were recently diagnosed with oral cancer were selected as cases. Two healthy controls were selected for each observed case and they were matched with age (+/- 5 years) gender and location. Use of different forms of tobacco such as cigarettes, pipe-smoking and shamma (smokeless-tobacco) was assessed. Khat, a commonly used chewing substance in the community was also included. Descriptive analysis was first performed followed by multiple logistic regression (with and without interaction) to derive odds ratios (ORs) and 95% confidence interval (CIs). Results: Mean age of the study sample (56% males and 44% females) was 65.3 years. Multinomial regression analysis revealed that shamma use increased the odds of developing oral cancer by 29 times (OR=29.3; 10.3-83.1). Cigarette (OR=6.74; 2.18-20.8) was also seen to have an effect. With the interaction model the odds ratio increased significantly for shamma users (OR=37.2; 12.3-113.2) and cigarette smokers (OR=10.5; 2.88-3.11). Khat was observed to have negative effect on the disease occurrence when used along with shamma (OR=0.01; 0.00 - 0.65). Conclusions: We conclude that shamma, a moist form of smokeless tobacco is a major threat for oral cancer occurrence in the Jazan region of Saudi Arabia. This study gives a direction to conduct further longitudinal studies in the region with increased sample size representing the population in order to provide more substantial evidence.