Normahira Mamat @ Mohamad Nor
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Preferred name
Normahira Mamat @ Mohamad Nor
Official Name
Normahira, Mamat @ Mohamad Nor
Alternative Name
Mamat, N.
Mamat, Normahira
Normahira, M.
Main Affiliation
Scopus Author ID
55986880900
Researcher ID
DEH-4271-2022

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Design and Development of Cascaded Current Control in DC Motor Variable Speed Drive using dSPACE

2023-01-01 , Ahmad Firdaus Ahmad Zaidi , Davendren T. , Syahrul Ashikin Azmi , Leong Jenn Hwai , Jenn , Kamarulzaman Kamarudin , Hassan A. , Hasimah Ali , Mohd Shuhanaz Zanar Azalan , Normahira Mamat @ Mohamad Nor

Even today, DC motors are still used in variety of applications, including home appliances, transportation, as well as industrial crane and rolling machine. However, achieving precise speed and torque control in DC drives at industry level could be challenging, as instability and reduced efficiency remains at large. This project focuses on developing a cascaded control system for a Separately Excited Brushed DC motor using dSPACE platform. The cascaded control system, designed using MATLAB Simulink, incorporates a proportional-integral (PI) controller at the speed loop and a Hysteresis controller at the current loop to improve robustness and dynamic performance. The experimental setup utilizes the dSPACE 1104 platform, an asymmetric bridge converter board, gate driver, and electrical load. Speed measurement is done using an incremental encoder, while current is measured using the ACS712 current sensor. The drive system was tested in alternate low and high speed cycle on various load level to test for stability, robustness and dynamic performance. The proposed control system was compared with PI-closed-loop control and open-loop control determine the best drive performance. Experimental results showed significant improvement in term of transient response and ripple reduction of speed and current for proposed cascaded current control over the closed-loop design.

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Cure Behaviour and Tensile Properties of Pineapple Leaf Fibre Reinforced Natural Rubber Composites

2024-03-01 , Xuan, Yeo Yi , Mohd Ridzuan Mohd Jamir , Mohd Shukry Abdul Majid , Mohd Shihabudin Ismail , Yudhanto F. , Normahira Mamat @ Mohamad Nor , Fauziah Che Mat

Short natural fibres replace synthetic fibres as filler in natural rubber (NR) as they are environmentally beneficial and sustainable. This study investigates the cure behaviour and tensile properties of pineapple leaf fibre (PALF) reinforced NR composites at various fibre contents. The fibre contents are varied at 0, 10, 20 and 30 parts per hundred rubber (phr). PALF reinforced NR composites are prepared using a two-roll mill. Surface morphology of tensile fractured specimens is examined using scanning electron microscopy (SEM). The results demonstrated that the optimum cure time decreases significantly with greater fibre content. The hardness value increases gradually with increasing filler content. The stress-strain graphs show an increasing trend in stress at higher fibre content particularly at low strain regions. On the contrary, the tensile strength reduces when the fibre content is increased up to 30 phr. SEM analysis reveals that the fibre-matrix adhesion is considerably poor due to the fibre pullout phenomenon observed. It is indicated that higher fibre content could be possibly reinforced to NR to achieve high deformation stress at incredibly low strain regions.

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Fabrication and characterization of β-tricalcium phosphate bone scaffold coated with κ-carrageenan and alginate natural polymers

2023 , Normahira Mamat @ Mohamad Nor , Mariatti Jaafar , Zuratul Ain Abdul Hamid , Badrul Hisham Yahaya

One scaffold with the complex characteristics is a challenging need, starting from the scaffold design stage until the transformation into in vivo stages. In this circumstance, the combination of bioceramics with polymers as coated scaffolds is gaining acceptance to enhance mechanical properties. Here, properties of porous B-tricalcium phosphate (B-TCP) scaffolds, coated with alginate and K-carrageenan, were investigated and compared with those of uncoated scaffolds. B-TCP scaffolds have been fabricated with 50 wt% and 60 wt% solid concentration using freeze-casting and replication methods. Natural polymers based on polysaccharides, K-carrageenan, and alginate solutions were used to coat and strengthen the B-TCP scaffold. The results suggest that the compressive strength of a coated B-TCP scaffold polymer is higher than an uncoated B-TCP scaffold, and that with 60 wt% solid concentration for both methods have the highest compressive strength. Alginate-coated B-TCP scaffolds exhibit slightly higher strength than K-carrageenan-coated scaffolds. For the cell viability test, no cell toxicity was found after 3 days of rabbit fibroblast cell culture. This study confirmed the importance of natural polymers phase in enhancing the scaffold strength while maintaining the interconnected pores size.

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Biodegradation of PLA-Pennisetum purpureum based biocomposite scaffold

2017-10-29 , Revati R. , Mohd Shukry Abdul Majid , Mohd Ridzuan Mohd Jamir , Normahira Mamat @ Mohamad Nor , Nashrul Fazli Mohd Nasir , Cheng Ee Meng

The in vitro degradation and mechanical properties of a 3D porous Pennisetum purpureum (PP)/polylactic acid (PLA) - based scaffold was investigated. In this study, composite scaffolds with PP to PLA ratio of 0%, 10%, 20%, and 30% were immersed in PBS solution at 37 °C for 40 days. Interestingly, the degradation rate was reduced for the PLA/PP20 scaffold, though insignificantly, this could be attributed to the improved mechanical properties and stronger fibre-matrix interface. The FESEM results indicated that a sound fibre-matrix interface was formed in the PLA/PP20 scaffold, which reflected the addition of P. purpureum into PLA decreasing the degradation rate compared to in pure PLA scaffolds. The results suggest that the P. purpureum/PLA scaffold degradation rate can be altered and controlled to meet the requirement imposed by a given tissue engineering application.

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In vitro biodegradation, cytotoxicity, and biocompatibility of polylactic acid/napier cellulose nanofiber scaffold composites

2022-12-31 , Revati R. , Mohd Shukry Abdul Majid , Mohd Ridzuan Mohd Jamir , Normahira Mamat @ Mohamad Nor , Cheng Ee Meng , Alshahrani H.A.

This study aimed to evaluate the bioactivities and biocompatibilities of porous polylactic acid (PLA) reinforced with cellulose nanofiber (CNF) scaffolds. The in vitro degradation behaviors of the porous PLA/CNF scaffolds were systematically measured for up to 8 weeks in a phosphate-buffered saline medium at 37 °C. The reinforcement of CNF resisted the biodegradation of the scaffolds. The in vitro cytotoxicity and biocompatibility of the scaffolds were determined using the Beas2B American Type Culture Collection cells. The 3-(4,5-cimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide cytotoxicity and proliferation tests showed that the scaffolds were non-toxic, and epithelial cells grew well on the scaffold after 7 days of culture, whereas the percentage of cell proliferation on the PLA/CNF15 scaffold was the largest, 130 %. A scratch wound-healing assay was performed to evaluate the suitability of the scaffolds for cell migration. The results demonstrated that the scaffolds exhibited good cell migration towards nearly complete wound closure.

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Biodegradation and swelling behaviour of cellulose-based plastic incorporation of pennisetum purpureum, chitosan and gelatine

2023-01-01 , Rohadi T.N.T. , Mohd Ridzuan Mohd Jamir , Mohd Shukry Abdul Majid , Normahira Mamat @ Mohamad Nor , Hussain H.S. , Xuan Y.Y.

This paper reports on the biodegradation and swelling behaviour of cellulose-based plastic incorporation of Pennisetum purpureum (PS), chitosan and gelatine. Cellulose-based plastic (CP) was obtained from chitosan and gelatin; and from the cortex (CPS), pith (PPS), and whole (WPS) of Pennisetum purpureum (PS). The films were prepared by solution casting with untreated, 4, 8, 12, 16, and 20% alkali-treated cellulose of CPS, PPS, and WPS. The ASTM D5988-method was used to conduct the CP biodegradation tests. The swelling behaviour test was performed to measure the swelling percentage for each CP samples in aqueous solution with different pH values. The results reveal that the biodegradation of untreated CPS (60.30%), untreated WPS (49.74%), and untreated PPS (CP) showed the biggest relative weight reduction. CP added with the 8, and 16% alkali-treated cellulose of CPS, and PPS continues swelling in the solution of pH 7 throughout 24 hours of analysis. Increasing the cellulose loading accelerated the biodegradation rate of the bioplastic films. The results also suggest that the CP with the incorporated cortex (CPS) of Pennisetum purpureum (PS), is the most water-resistant in neutral followed by acid and alkali.

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Influence of cellulose filler extracted from napier grass on thermal characterizations, moisture content, tensile strength, biodegradation, and morphological structure of bioplastic films

2022-01-01 , Tuan Rohadi T.N. , Mohd Ridzuan Mohd Jamir , Mohd Shukry Abdul Majid , Normahira Mamat @ Mohamad Nor , Sulaiman M.H.

This paper reports on the effects of Napier grass (NG) cellulose used as a filler on the thermal characterizations, moisture content, tensile strength, biodegradation, and morphological structure of bioplastic films. Bioplastic films were obtained from chitosan and gelatin; and from the fiber, bark, and whole of Napier grass (NG). The films were prepared by solution casting with 1, 1.5, 2, and 2.5 wt.% of cellulose content. Alkali and bleaching treatments were performed on the cellulose using 8% sodium hydroxide and 1.7% sodium chlorite. The results reveal that the tensile strength of the bioplastic film with 2 wt.% of fiber filler was the highest and decreased when the cellulose filler loading was 2.5 wt.%. Increasing the cellulose loading accelerated the biodegradation rate of the bioplastic films. The addition of the fiber filler had improved compatibility among the components and the barrier properties of the film that led to a less-porous film.

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