50 results on '"Hafidz A"'
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2. Hotelling T2 Control Chart for Detecting Changes in Mortality Models Based on Machine-Learning Decision Tree
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Rakhmawan, Suryo Adi, primary, Omar, M. Hafidz, additional, Riaz, Muhammad, additional, and Abbas, Nasir, additional
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- 2023
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3. Microarray Profiling of Differentially Expressed Genes in Coronary Artery Bypass Grafts of High-Risk Patients with Postoperative Cognitive Dysfunctions
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Yazit, Noor Anisah Abu, primary, Juliana, Norsham, additional, Kadiman, Suhaini, additional, Hafidz, Kamilah Muhammad, additional, Mohd Fahmi Teng, Nur Islami, additional, Abdul Hamid, Nazefah, additional, Effendy, Nadia, additional, Azmani, Sahar, additional, Abu, Izuddin Fahmy, additional, Aziz, Nur Adilah Shuhada Abd, additional, and Das, Srijit, additional
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- 2023
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4. Isotopic Tracer for Absolute Quantification of Metabolites of the Pentose Phosphate Pathway in Bacteria
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Mohd Kamal, Khairunnisa, primary, Mahamad Maifiah, Mohd Hafidz, additional, Zhu, Yan, additional, Abdul Rahim, Nusaibah, additional, Hashim, Yumi Zuhanis Has-Yun, additional, and Abdullah Sani, Muhamad Shirwan, additional
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- 2022
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5. Spatial Distribution of COVID-19 Infected Cases in Kelantan, Malaysia
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Nor, Amal Najihah Muhamad, primary, Jamil, Rohazaini Muhammad, additional, Aziz, Hasifah Abdul, additional, Abas, Muhamad Azahar, additional, Hambali, Kamarul Ariffin, additional, Hassin, Nor Hizami, additional, Abdul Karim, Muhammad Firdaus, additional, Nawawi, Siti Aisyah, additional, Amir, Aainaa, additional, Amaludin, Nazahatul Anis, additional, Ibrahim, Norfadhilah, additional, Yusoff, Abdul Hafidz, additional, Malek, Nur Hanisah Abdul, additional, Rafaai, Nur Hairunnisa, additional, Mohd Hatta, Siti Khairiyah, additional, and Grafius, Darren, additional
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- 2022
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6. Fabrication and Characterisation of MWCNT/Polyvinyl (PVC) Polymer Inclusion Membrane for Zinc (II) Ion Removal from Aqueous Solution
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Khalid, Nadia Aqilah, primary, Shoparwe, Noor Fazliani, additional, Yusoff, Abdul Hafidz, additional, Sulaiman, Ahmad Ziad, additional, Ahmad, Abdul Latif, additional, and Azmi, Nur Aina, additional
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- 2022
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7. Effect of Graphene Oxide on the Properties of Polymer Inclusion Membranes for Gold Extraction from Acidic Solution
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Husna, Siti Madiha, primary, Yusoff, Abdul Hafidz, additional, Mohan, Mythili, additional, Azmi, Nur Aina, additional, Ter, Teo Pao, additional, Shoparwe, Noor Fazliani, additional, and Sulaiman, Ahmad Ziad, additional
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- 2022
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8. Hybrid Nanofluid Radiative Mixed Convection Stagnation Point Flow Past a Vertical Flat Plate with Dufour and Soret Effects
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Wahid, Nur Syahirah, primary, Arifin, Norihan Md, additional, Khashi’ie, Najiyah Safwa, additional, Pop, Ioan, additional, Bachok, Norfifah, additional, and Hafidzuddin, Mohd Ezad Hafidz, additional
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- 2022
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9. Pasteurellosis Vaccine Commercialization: Physiochemical Factors for Optimum Production
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Oslan, Siti Nur Hazwani, primary, Tan, Joo Shun, additional, Yusoff, Abdul Hafidz, additional, Sulaiman, Ahmad Ziad, additional, Awang, Mohd Azrie, additional, Lazim, Azwan Mat, additional, Lim, Si Jie, additional, Oslan, Siti Nurbaya, additional, Saad, Mohd Zamri, additional, and Ariff, Arbakariya B., additional
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- 2022
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10. Effect of Stability of Two-Dimensional (2D) Aminoethyl Methacrylate Perovskite Using Lead-Based Materials for Ammonia Gas Sensor Application
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Mat Yunin, Muhamad Yuzaini Azrai, primary, Mohd Adenam, Norfatihah, additional, Khairul, Wan M., additional, Yusoff, Abdul Hafidz, additional, and Adli, Hasyiya Karimah, additional
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- 2022
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11. Bioprocess Strategy of Haematococcus lacustris for Biomass and Astaxanthin Production Keys to Commercialization: Perspective and Future Direction
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Oslan, Siti Nur Hazwani, primary, Oslan, Siti Nurbaya, additional, Mohamad, Rosfarizan, additional, Tan, Joo Shun, additional, Yusoff, Abdul Hafidz, additional, Matanjun, Patricia, additional, Mokhtar, Ruzaidi Azli Mohd, additional, Shapawi, Rossita, additional, and Huda, Nurul, additional
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- 2022
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12. Microarray Profiling of Differentially Expressed Genes in Coronary Artery Bypass Grafts of High-Risk Patients with Postoperative Cognitive Dysfunctions
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Noor Anisah Abu Yazit, Norsham Juliana, Suhaini Kadiman, Kamilah Muhammad Hafidz, Nur Islami Mohd Fahmi Teng, Nazefah Abdul Hamid, Nadia Effendy, Sahar Azmani, Izuddin Fahmy Abu, Nur Adilah Shuhada Abd Aziz, and Srijit Das
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cognitive decline ,microarray ,differentially expressed genes ,CABG ,Health, Toxicology and Mutagenesis ,Public Health, Environmental and Occupational Health - Abstract
Postoperative cognitive dysfunction (POCD) is cognitive decline after surgery. The authors hypothesized that gene-level changes could be involved in the pathogenesis of POCD. The present study evaluated the incidence of POCD and its associated differentially expressed genes. This was a prospective cohort study conducted on high-risk coronary artery bypass graft patients aged 40 to 75 years. POCD classification was based on a one standard deviation decline in the postoperative scores compared to the preoperative scores. The differentially expressed genes were identified using microarray analysis and validated using quantitative RT-PCR. Forty-six patients were recruited and completed the study. The incidence of POCD was identified using a set of neurocognitive assessments and found to be at 17% in these high-risk CABG patients. Six samples were selected for the gene expression analyses (3 non-POCD and 3 POCD samples). The findings showed five differentially expressed genes in the POCD group compared to the non-POCD group. The upregulated gene was ERFE, whereas the downregulated genes were KIR2DS2, KIR2DS3, KIR3DL2, and LIM2. According to the results, the gene expression profiles of POCD can be used to find potential proteins for POCD diagnostic and predictive biomarkers. Understanding the molecular mechanism of POCD development will further lead to early detection and intervention to reduce the severity of POCD, and hence, reduce the mortality and morbidity rate due to the condition.
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- 2023
13. Spatial Distribution of COVID-19 Infected Cases in Kelantan, Malaysia
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Amal Najihah Muhamad Nor, Rohazaini Muhammad Jamil, Hasifah Abdul Aziz, Muhamad Azahar Abas, Kamarul Ariffin Hambali, Nor Hizami Hassin, Muhammad Firdaus Abdul Karim, Siti Aisyah Nawawi, Aainaa Amir, Nazahatul Anis Amaludin, Norfadhilah Ibrahim, Abdul Hafidz Yusoff, Nur Hanisah Abdul Malek, Nur Hairunnisa Rafaai, Siti Khairiyah Mohd Hatta, and Darren Grafius
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spatial distribution ,COVID-19 model map ,population density ,infected cases ,Kelantan ,Malaysia ,Renewable Energy, Sustainability and the Environment ,Geography, Planning and Development ,Building and Construction ,Management, Monitoring, Policy and Law - Abstract
Kota Bharu city in Kelantan, Malaysia was reported with the highest cases of coronavirus disease 2019 (COVID-19) among other districts. Kota Bharu is the capital city of Kelantan, which acts as the administrative, commercial, and financial areas. A large population pool may become a potential carrier for disease transmission to become an epidemic. However, the impact of population density on the COVID-19 outbreak in Malaysia is still unknown and undiscovered. Therefore, this study investigates the impact of population density on COVID-19 as a potential virus transmission carrier using linear regression models. The chances of formulating new strategies for combating COVID-19 are higher when the driver of transmission potential is identified. This study shows that the highest value of infected area density is in Kota Bharu (0.76), while the infected risk area was highest in Jeli (0.33). This study found that there is a strong relationship between COVID-19 infection cases in Kelantan and population density (R2 which is 0.845). Therefore, high population density was identified as a potential driver of transmission of COVID-19 outbreak. Understanding the potential drivers of the disease in a local setting is very important for better preparation and management. The outcome of the study can aid in the development of a new analytical model for strategic planning of Zero COVID-19 for securing the public health and wellness, both social and economic, by researchers, scientists, planners, resource managers, and decision-makers.
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- 2022
14. Effect of Graphene Oxide on the Properties of Polymer Inclusion Membranes for Gold Extraction from Acidic Solution
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Siti Madiha Husna, Abdul Hafidz Yusoff, Mythili Mohan, Nur Aina Azmi, Teo Pao Ter, Noor Fazliani Shoparwe, and Ahmad Ziad Sulaiman
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Process Chemistry and Technology ,Chemical Engineering (miscellaneous) ,Filtration and Separation ,polymer inclusion membrane (PIM) ,graphene oxide (GO) ,membrane characterization ,gold extraction - Abstract
The cyanidation leaching method is hazardous to the environment, but it is widely applied in the gold mining process because it is effective for gold extraction. This study fabricates polymer inclusion membranes (PIMs), which have environment-friendly properties, with graphene oxide (GO) as an alternative to the cyanidation leaching method for gold extraction. Poly(vinylidenefluoride-co-hexa-fluoropropylene)-based PIMs with different GO concentrations in five membranes (i.e., M1 (0 wt.%), M2 (0.5 wt.%), M3 (1.0 wt.%), M4 (1.5 wt.%), and M5 (2.0 wt.%)) are studied for their potential to extract gold from a hydrochloric acid solution. The membranes are prepared using di-(2-ethylhexyl) phosphoric acid as the extractant and dioctyl phthalate as the plasticizer. Scanning electron microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, ion exchange capacity, and water uptake are used to characterize the physical and chemical properties of the fabricated PIMs. The results show that the optimized membrane for gold extraction is M4 (1.5 wt.% GO), which yields a better performance on thermal stability, ion exchange capacity (IEC), and water uptake. M4 (1.5 wt.% GO) also exhibits a smooth and dense structure, with the maximum extraction efficiency obtained at 84.71% of extracted gold. In conclusion, PIMs can be used as an alternative for extracting gold with a better performance by the presence of 1.5 wt.% GO in membrane composition.
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- 2022
15. Hybrid Nanofluid Radiative Mixed Convection Stagnation Point Flow Past a Vertical Flat Plate with Dufour and Soret Effects
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Nur Syahirah Wahid, Norihan Md Arifin, Najiyah Safwa Khashi’ie, Ioan Pop, Norfifah Bachok, and Mohd Ezad Hafidz Hafidzuddin
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General Mathematics ,Computer Science (miscellaneous) ,Engineering (miscellaneous) ,hybrid nanofluid ,stagnation point ,Dufour and Soret effects ,mixed convection ,radiation ,numerical solutions ,stability analysis - Abstract
The widespread application of hybrid nanofluid in real applications has been accompanied by a large increase in computational and experimental research. Due to the unique characteristics of hybrid nanofluid, this study aspires to examine the steady two-dimensional mixed convection stagnation point flow of a hybrid nanofluid past a vertical plate with radiation, Dufour, and Soret effects, numerically. The formulations of the specific flow model are presented in this study. The model of fluid flow that is expressed in the form of partial differential equations is simplified into ordinary differential equations via the transformation of similarity, and then solved numerically by using the boundary value problem solver known as bvp4c in MATLAB, which implements the finite difference scheme with the Lobatto IIIa formula. Two possible numerical solutions can be executed, but only the first solution is stable and meaningful from a physical perspective when being evaluated via a stability analysis. According to the findings, it is sufficient to prevent the boundary layer separation by using 2% copper nanoparticles and considering the lesser amount of Dufour and Soret effects. The heat transfer rate was effectively upgraded by minimizing the volume fraction of copper and diminishing the Dufour effect. Stronger mixed convection would lead to maximum skin friction, mass transfer, and heat transfer rates. This important preliminary research will give engineers and scientists the insight to properly control the flow of fluids in optimizing the related complicated systems.
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- 2022
16. Evolution of Green Space under Rapid Urban Expansion in Southeast Asian Cities
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Muhamad Nor, Amal Najihah, primary, Abdul Aziz, Hasifah, additional, Nawawi, Siti Aisyah, additional, Muhammad Jamil, Rohazaini, additional, Abas, Muhamad Azahar, additional, Hambali, Kamarul Ariffin, additional, Yusoff, Abdul Hafidz, additional, Ibrahim, Norfadhilah, additional, Rafaai, Nur Hairunnisa, additional, Corstanje, Ron, additional, Harris, Jim, additional, Grafius, Darren, additional, and Perotto-Baldivieso, Humberto L., additional
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- 2021
- Full Text
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17. Pasteurellosis Vaccine Commercialization: Physiochemical Factors for Optimum Production
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Siti Nur Hazwani Oslan, Joo Shun Tan, Abdul Hafidz Yusoff, Ahmad Ziad Sulaiman, Mohd Azrie Awang, Azwan Mat Lazim, Si Jie Lim, Siti Nurbaya Oslan, Mohd Zamri Saad, and Arbakariya B. Ariff
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Process Chemistry and Technology ,Chemical Engineering (miscellaneous) ,Bioengineering - Abstract
Pasteurella spp. are Gram-negative facultative bacteria that cause severe economic and animal losses. Pasteurella-based vaccines are the most promising solution for controlling Pasteurella spp. outbreaks. Remarkably, insufficient biomass cultivation (low cell viability and productivity) and lack of knowledge about the cultivation process have impacted the bulk production of animal vaccines. Bioprocess optimization in the shake flask and bioreactor is required to improve process efficiency while lowering production costs. However, its state of the art is limited in providing insights on its biomass upscaling, preventing a cost-effective vaccine with mass-produced bacteria from being developed. In general, in the optimum cultivation of Pasteurella spp., production factors such as pH (6.0–8.2), agitation speed (90–500 rpm), and temperature (35–40 °C) are used to improve production yield. Hence, this review discusses the production strategy of Pasteurella and Mannheimia species that can potentially be used in the vaccines for controlling pasteurellosis. The physicochemical factors related to operational parameter process conditions from a bioprocess engineering perspective that maximize yields with minimized production cost are also covered, with the expectation of facilitating the commercialization process.
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- 2022
18. An Adaptive EWMA Control Chart Based on Principal Component Method to Monitor Process Mean Vector
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Muhammad Riaz, Babar Zaman, Ishaq Adeyanju Raji, M. Hafidz Omar, Rashid Mehmood, and Nasir Abbas
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General Mathematics ,average run length ,control charts ,Monte Carlo simulation ,multivariate CUSUM ,principal component ,Computer Science (miscellaneous) ,Engineering (miscellaneous) - Abstract
The special causes of variations, which is also known as a shift, can occur in a single or more than one related process characteristics. Statistical process control tools such as control charts are useful to monitor shifts in the process parameters (location and/or dispersion). In real-life situation, the shift is emerging in different sizes, and it is hard to identify it with classical control charts. Moreover, more than one process of characteristics required special attention because they must monitor jointly due to the association among them. This study offers two adaptive control charts to monitor the different sizes of a shift in the process mean vector. The novelty behind this study is to use dimensionally reduction techniques such as principal component analysis (PCA) and an adaptive method such as Huber and Bi-square functions. In brief, the multivariate cumulative sum control chart based on PCA is designed, and its plotting statistic is utilized as an input in the classical exponentially weighted moving average (EWMA) control chart. The run length (RL) properties of the proposed and other control charts are obtained by designing algorithms in MATLAB through a Monte Carlo simulation. For a single shift, the performance of the control charts is assessed through an average of RL, standard deviation of RL, and standard error of RL. Likewise, overall performance measures such as extra quadratic loss, relative ARL, and the performance comparison index are also used. The comparison reveals the superiority over other control charts. Furthermore, to emphasize the application process and benefits of the proposed control charts, a real-life example of the wind turbine process is included.
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- 2022
19. Inverse Maxwell Distribution and Statistical Process Control: An Efficient Approach for Monitoring Positively Skewed Process
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M. Hafidz Omar, M. Pear Hossain, Muhammad Riaz, and Sheikh Y. Arafat
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Physics and Astronomy (miscellaneous) ,Computer science ,General Mathematics ,Inverse ,average run length ,02 engineering and technology ,inverse Maxwell distribution ,lognormal s-chart ,01 natural sciences ,010104 statistics & probability ,symbols.namesake ,Chart ,0202 electrical engineering, electronic engineering, information engineering ,Computer Science (miscellaneous) ,statistical process control ,Applied mathematics ,Control chart ,0101 mathematics ,Weibull distribution ,lcsh:Mathematics ,brake pad ,Statistical process control ,lcsh:QA1-939 ,Maxwell–Boltzmann distribution ,Chemistry (miscellaneous) ,symbols ,020201 artificial intelligence & image processing ,Step detection ,Scale parameter - Abstract
(1) Background: The literature discusses the inverse Maxwell distribution theoretically without application. Control charting is promising, but needs development for inverse Maxwell processes. (2) Methods: Thus, we develop the VIM control chart for monitoring the inverse Maxwell scale parameter and studied its statistical properties. The chart’s performance is evaluated using power curves and run length properties. (3) Results: Further, we use simulated data to compare the shift detection capability of our chart with Weibull, gamma, and lognormal charts. (4) Conclusion: The analysis demonstrates our chart’s efficiency for monitoring skewed processes. Finally, we apply our chart for monitoring real world lifetimes of car brake pads.
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- 2021
20. Bioprocess Strategy of Haematococcus lacustris for Biomass and Astaxanthin Production Keys to Commercialization: Perspective and Future Direction
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Siti Nur Hazwani Oslan, Siti Nurbaya Oslan, Rosfarizan Mohamad, Joo Shun Tan, Abdul Hafidz Yusoff, Patricia Matanjun, Ruzaidi Azli Mohd Mokhtar, Rossita Shapawi, and Nurul Huda
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Plant Science ,Biochemistry, Genetics and Molecular Biology (miscellaneous) ,Food Science - Abstract
Haematococcus lacustris (formerly called Haematococcus pluvialis) is regarded as the most promising microalgae for the production of natural astaxanthin, which is secondary metabolism used as a dietary supplement, also for cosmetic applications, due to its high anti-oxidant activity. Astaxanthin has a wide range of biological activities and high economic potential, and currently dominates the market in its synthetic form. Furthermore, because of the difficulty of bioprocess and the high cost of cultivation, astaxanthin extracted from this microalga is still expensive due to its low biomass and pigment productivities. Large-scale biomass production in biotechnological production necessitates the processing of a large number of cultures as well as the use of both indoor and outdoor systems, such as open pond raceway systems and photo-bioreactors (PBR). The photo-bioreactors systems are suitable for mass production because growth conditions can be controlled, and the risk of contamination can be reduced to a certain extent and under specific culture parameters. This review discusses current technologies being developed to improve cultivation and operation efficiency and profitability, as well as the effect of parameter factors associated with H. lacustris cultivation on biomass and astaxanthin bioproduction, and even strategies for increasing bioproduction and market potential for H. lacustris astaxanthin.
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- 2022
21. Application of General Full Factorial Statistical Experimental Design’s Approach for the Development of Sustainable Clay-Based Ceramics Incorporated with Malaysia’s Electric Arc Furnace Steel Slag Waste
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Teo, Pao Ter, primary, Zakaria, Siti Koriah, additional, Mohd Sharif, Nurulakmal, additional, Abu Seman, Anasyida, additional, Taib, Mustaffa Ali Azhar, additional, Mohamed, Julie Juliewatty, additional, Yusoff, Mahani, additional, Yusoff, Abdul Hafidz, additional, Mohamad, Mardawani, additional, Ali, Arlina, additional, and Masri, Mohamad Najmi, additional
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- 2021
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22. A Review on Haematococcus pluvialis Bioprocess Optimization of Green and Red Stage Culture Conditions for the Production of Natural Astaxanthin
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Oslan, Siti Nur Hazwani, primary, Shoparwe, Noor Fazliani, additional, Yusoff, Abdul Hafidz, additional, Rahim, Ainihayati Abdul, additional, Chang, Chang Shen, additional, Tan, Joo Shun, additional, Oslan, Siti Nurbaya, additional, Arumugam, Kavithraashree, additional, Ariff, Arbakariya Bin, additional, Sulaiman, Ahmad Ziad, additional, and Mohamed, Mohd Shamzi, additional
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- 2021
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23. Inverse Maxwell Distribution and Statistical Process Control: An Efficient Approach for Monitoring Positively Skewed Process
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Omar, M. Hafidz, primary, Arafat, Sheikh Y., additional, Hossain, M. Pear, additional, and Riaz, Muhammad, additional
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- 2021
- Full Text
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24. Essential Medicines in Universal Health Coverage: A Scoping Review of Public Health Law Interventions and How They Are Measured in Five Middle-Income Countries
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Perehudoff, Katrina, primary, Demchenko, Ivan, additional, Alexandrov, Nikita V., additional, Brutsaert, David, additional, Ackon, Angela, additional, Durán, Carlos E., additional, El-Dahiyat, Faris, additional, Hafidz, Firdaus, additional, Haque, Rezwan, additional, Hussain, Rabia, additional, Salenga, Roderick, additional, Suleman, Fatima, additional, and Babar, Zaheer-Ud-Din, additional
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- 2020
- Full Text
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25. Assessment of Electric Arc Furnace (EAF) Steel Slag Waste’s Recycling Options into Value Added Green Products: A Review
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Teo, Pao Ter, primary, Zakaria, Siti Koriah, additional, Salleh, Siti Zuliana, additional, Taib, Mustaffa Ali Azhar, additional, Mohd Sharif, Nurulakmal, additional, Abu Seman, Anasyida, additional, Mohamed, Julie Juliewatty, additional, Yusoff, Mahani, additional, Yusoff, Abdul Hafidz, additional, Mohamad, Mardawani, additional, Masri, Mohamad Najmi, additional, and Mamat, Sarizam, additional
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- 2020
- Full Text
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26. Resorcinol-Formaldehyde (RF) as a Novel Plasticizer for Starch-Based Solid Biopolymer Electrolyte
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Selvanathan, Vidhya, primary, Ruslan, Mohd Hafidz, additional, Aminuzzaman, Mohammod, additional, Muhammad, Ghulam, additional, Amin, N., additional, Sopian, Kamaruzzaman, additional, and Akhtaruzzaman, Md., additional
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- 2020
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27. Organosoluble Starch-Cellulose Binary Polymer Blend as a Quasi-Solid Electrolyte in a Dye-Sensitized Solar Cell
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Selvanathan, Vidhya, primary, Yahya, Rosiyah, additional, Ruslan, Mohd Hafidz, additional, Sopian, Kamaruzzaman, additional, Amin, Nowshad, additional, Nour, Majid, additional, Sindi, Hatem, additional, Rawa, Muhyaddin, additional, and Akhtaruzzaman, Md., additional
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- 2020
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28. Long-Term Aerosol Trends and Variability over Central Saudi Arabia Using Optical Characteristics from Solar Village AERONET Measurements
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Al Otaibi, Mohammed, primary, Farahat, Ashraf, additional, Tawabini, Bassam, additional, Omar, M. Hafidz, additional, Ramadan, Emad, additional, Abuelgasim, Abdelgadir, additional, and P. Singh, Ramesh, additional
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- 2019
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29. Mixed Convective Flow and Heat Transfer of a Dual Stratified Micropolar Fluid Induced by a Permeable Stretching/Shrinking Sheet
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Khashi’ie, Najiyah Safwa, primary, Md Arifin, Norihan, additional, Nazar, Roslinda, additional, Hafidzuddin, Ezad Hafidz, additional, Wahi, Nadihah, additional, and Pop, Ioan, additional
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- 2019
- Full Text
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30. A Stability Analysis for Magnetohydrodynamics Stagnation Point Flow with Zero Nanoparticles Flux Condition and Anisotropic Slip
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Nadihah Wahi, Ezad Hafidz Hafidzuddin, Najiyah Safwa Khashi'ie, Norihan Md Arifin, Roslinda Mohd. Nazar, and Ioan Pop
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Control and Optimization ,Materials science ,Differential equation ,020209 energy ,Energy Engineering and Power Technology ,02 engineering and technology ,Slip (materials science) ,three-dimensional flow ,stability analysis ,lcsh:Technology ,Thermophoresis ,Physics::Fluid Dynamics ,Nanofluid ,nanofluid ,stagnation sheet ,slip condition ,Mass transfer ,0202 electrical engineering, electronic engineering, information engineering ,Electrical and Electronic Engineering ,Engineering (miscellaneous) ,Brownian motion ,Renewable Energy, Sustainability and the Environment ,lcsh:T ,Mechanics ,021001 nanoscience & nanotechnology ,Nonlinear system ,Physics::Space Physics ,Heat transfer ,0210 nano-technology ,Energy (miscellaneous) - Abstract
The numerical study of nanofluid stagnation point flow coupled with heat and mass transfer on a moving sheet with bi-directional slip velocities is emphasized. A magnetic field is considered normal to the moving sheet. Buongiorno’s model is utilized to assimilate the mixed effects of thermophoresis and Brownian motion due to the nanoparticles. Zero nanoparticles’ flux condition at the surface is employed, which indicates that the nanoparticles’ fraction are passively controlled. This condition makes the model more practical for certain engineering applications. The continuity, momentum, energy and concentration equations are transformed into a set of nonlinear ordinary (similarity) differential equations. Using bvp4c code in MATLAB software, the similarity solutions are graphically demonstrated for considerable parameters such as thermophoresis, Brownian motion and slips on the velocity, nanoparticles volume fraction and temperature profiles. The rate of heat transfer is reduced with the intensification of the anisotropic slip (difference of two-directional slip velocities) and the thermophoresis parameter, while the opposite result is obtained for the mass transfer rate. The study also revealed the existence of non-unique solutions on all the profiles, but, surprisingly, dual solutions exist boundlessly for any positive value of the control parameters. A stability analysis is implemented to assert the reliability and acceptability of the first solution as the physical solution.
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- 2019
31. Assessment of Electric Arc Furnace (EAF) Steel Slag Waste’s Recycling Options into Value Added Green Products: A Review
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Mahani Yusoff, Pao Ter Teo, Abdul Hafidz Yusoff, Sarizam Mamat, Anasyida Abu Seman, Mustaffa Ali Azhar Taib, Siti Koriah Zakaria, Siti Zuliana Salleh, Mohamad Najmi Masri, Julie Juliewatty Mohamed, Mardawani Mohamad, and Nurulakmal Mohd Sharif
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lcsh:TN1-997 ,0211 other engineering and technologies ,Scrap ,02 engineering and technology ,EAF steel slag ,Raw material ,law.invention ,law ,021105 building & construction ,Added value ,General Materials Science ,lcsh:Mining engineering. Metallurgy ,Electric arc furnace ,Waste management ,Malaysian steelmaking industry ,business.industry ,Metals and Alloys ,Slag ,021001 nanoscience & nanotechnology ,Steelmaking ,Portland cement ,Wastewater ,visual_art ,visual_art.visual_art_medium ,Environmental science ,0210 nano-technology ,business ,recycle options of EAF slag - Abstract
Steel slag is one of the most common waste products from the steelmaking industry. Conventional methods of slag disposal can cause negative impacts on humans and the environment. In this paper, the process of steel and steel slag production, physical and chemical properties, and potential options of slag recycling were reviewed. Since steel is mainly produced through an electric arc furnace (EAF) in Malaysia, most of the recycling options reviewed in this paper focused on EAF slag and the strengths and weaknesses of each recycle option were outlined. Based on the reports from previous studies, it was found that only a portion of EAF slag is recycled into more straightforward, but lower added value applications such as aggregates for the construction industry and filter/absorber for wastewater treatments. On the other hand, higher added value recycling options for EAF slag that are more complicated such as incorporated as raw material for Portland cement and ceramic building materials remain at the laboratory testing stage. The main hurdle preventing EAF slag from being incorporated as a raw material for higher added value industrial applications is its inconsistent chemical composition. The chemical composition of EAF slag can vary based on the scrap metal used for steel production. For this, mineral separation techniques can be introduced to classify the EAF slag base on its physical and chemical compositions. We concluded that future research on recycling EAF slag should focus on separation techniques that diversify the recycling options for EAF slag, thereby increasing the waste product’s recycling rate.
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- 2020
32. Resorcinol-Formaldehyde (RF) as a Novel Plasticizer for Starch-Based Solid Biopolymer Electrolyte
- Author
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Ghulam Muhammad, Mohammod Aminuzzaman, Kamaruzzaman Sopian, Akhtaruzzaman, Nowshad Amin, Vidhya Selvanathan, and Mohd Hafidz Ruslan
- Subjects
Materials science ,Polymers and Plastics ,Starch ,education ,plasticization ,Electrolyte ,Conductivity ,engineering.material ,Article ,lcsh:QD241-441 ,chemistry.chemical_compound ,Crystallinity ,lcsh:Organic chemistry ,Ionic conductivity ,lithium triflate ,starch ,resorcinol-formaldehyde ,Plasticizer ,food and beverages ,General Chemistry ,Chemical engineering ,chemistry ,ionic conductivity ,engineering ,polymer electrolyte ,Biopolymer ,Trifluoromethanesulfonate - Abstract
A starch-resorcinol-formaldehyde (RF)-lithium triflate (LiTf) based biodegradable polymer electrolyte membrane was synthesized via the solution casting technique. The formation of RF crosslinks in the starch matrix was found to repress the starch&rsquo, s crystallinity as indicated by the XRD data. Incorporation of the RF plasticizer improved the conductivity greatly, with the highest room-temperature conductivity recorded being 4.29 ×, 10&minus, 4 S cm&minus, 1 achieved by the starch:LiTf:RF (20 wt.%:20 wt.%:60 wt.%) composition. The enhancement in ionic conductivity was an implication of the increase in the polymeric amorphous region concurrent with the suppression of the starch&rsquo, s crystallinity. Chemical complexation between the plasticizer, starch, and lithium salt components in the electrolyte was confirmed by FTIR spectra.
- Published
- 2020
33. Long-Term Aerosol Trends and Variability over Central Saudi Arabia Using Optical Characteristics from Solar Village AERONET Measurements
- Author
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Ramesh P. Singh, Abdelgadir Abuelgasim, Mohammed Al Otaibi, Emad Ramadan, Ashraf Farahat, Bassam Tawabini, and M. Hafidz Omar
- Subjects
optical properties ,Atmospheric Science ,Angstrom exponent ,010504 meteorology & atmospheric sciences ,education ,Saudi Arabia ,Air pollution ,HYSPLIT ,010501 environmental sciences ,Environmental Science (miscellaneous) ,Atmospheric sciences ,medicine.disease_cause ,complex mixtures ,01 natural sciences ,air pollution ,Dust storm ,Radiation budget ,parasitic diseases ,medicine ,Precipitation ,0105 earth and related environmental sciences ,respiratory system ,AERONET ,Aerosol ,Solar Village ,Environmental science ,geographic locations - Abstract
Natural and anthropogenic aerosols over the Kingdom of Saudi Arabia (KSA) play a major role in affecting the regional radiation budget. The long-term variability of these aerosols&rsquo, physical and optical parameters, including aerosol optical depth (AOD) and Å, ngströ, m exponent (&alpha, ), were measured at a location near central KSA using the Solar Village (SV) AERONET (Aerosol Robotic Network) station during the period December 1999&ndash, January 2013. The AERONET measurements show an overall increase in AOD on an annual basis. This upward trend is mainly attributed to a prolonged increase in the monthly/seasonal mean AOD during March&ndash, June and during August&ndash, September. In contrast, lower AOD values were observed during November&ndash, December. This can be attributed to a low frequency of dust outbreaks and higher precipitation rates. An overall, weak declining trend in &alpha, was observed, except during the summer. The spring and summer seasons experienced a pronounced increase in the number of coarse particles (~2 µ, m) during April 2006&ndash, January 2013 as compared to December 1999&ndash, March 2006, suggesting an increase in natural aerosol loadings. Using the HYSPLIT model, it was found that the March 2009 dust storm contributed to the mixing of long-transported dust with anthropogenic local emissions near the SV. The results suggest that extensive industrial activity contributed to the increase of anthropogenic emissions over KSA during the period April 2006&ndash, January 2013.
- Published
- 2019
34. Mixed Convective Flow and Heat Transfer of a Dual Stratified Micropolar Fluid Induced by a Permeable Stretching/Shrinking Sheet
- Author
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Najiyah Safwa Khashi'ie, Ezad Hafidz Hafidzuddin, Roslinda Mohd. Nazar, Norihan Md Arifin, Nadihah Wahi, and Ioan Pop
- Subjects
Materials science ,Buoyancy ,020209 energy ,General Physics and Astronomy ,Stratification (water) ,stretching/shrinking sheet ,02 engineering and technology ,engineering.material ,Article ,Physics::Fluid Dynamics ,Combined forced and natural convection ,Mass transfer ,0202 electrical engineering, electronic engineering, information engineering ,Partial differential equation ,Mechanics ,double stratification ,021001 nanoscience & nanotechnology ,Nusselt number ,micropolar fluid ,dual solutions ,Heat transfer ,engineering ,Magnetohydrodynamics ,magnetohydrodynamics ,0210 nano-technology ,mixed convection - Abstract
The present study accentuates the magnetohydrodynamics (MHD) flow and heat transfer characteristics of a dual stratified micropolar fluid over a permeable stretching/shrinking sheet. Thermal and solutal buoyancy forces are also included to incorporate with the stratification effect. Similarity, transformation is applied to reduce the governing model (partial differential equations) into a set of nonlinear ordinary differential equations (ODEs) due to its complexity. Using bvp4c solver in the MATLAB software, numerical results for some limiting cases are in favorable agreement with the earlier published results. Both assisting and opposing buoyancy flows have dual similarity solutions within specific range of suction and stretching/shrinking parameters, whereas only a distinctive solution is observed for pure forced convective flow. The micropolar fluid shows a disparate pattern of flow, heat and mass transfer characteristics between stretching and shrinking cases. Unlike the shrinking flow, the surface velocity gradient, local Nusselt and Sherwood numbers for stretching flow intensify with the increment of the material parameter. The result from stability analysis reveals that the first solution is the real solution, whereas the second solution is virtual.
- Published
- 2019
35. Variations in the Concentration of Magnetic Minerals and Heavy Metals in Suspended Sediments from Citarum River and Its Tributaries, West Java, Indonesia
- Author
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Satria Bijaksana, Irwan Iskandar, Nono Agus Santoso, Abd Hafidz, Sudarningsih Sudarningsih, Widodo Widodo, Rizky Ramdani, Silvia Jannatul Fajar, Darharta Dahrin, and Aditya Pratama
- Subjects
Citarum River ,volcanic area ,magnetic method ,magnetic susceptibility ,Zn content ,West Java ,heavy metal pollution ,tropical climate conditions ,Water supply ,West java ,010501 environmental sciences ,010502 geochemistry & geophysics ,01 natural sciences ,Tributary ,Temperate climate ,0105 earth and related environmental sciences ,Hydrology ,geography ,geography.geographical_feature_category ,business.industry ,lcsh:QE1-996.5 ,Sediment ,Tropics ,lcsh:Geology ,Volcano ,General Earth and Planetary Sciences ,Catchment area ,business - Abstract
The Citarum River has a volcanic catchment area in West Java Province, and is one of the nationally strategic rivers in tropical Indonesia due to its roles in water supply and in power generation. The river is economically important, but it is also polluted by industrial, agricultural, and residential wastes. Suspended sediment samples were collected along a certain section of the Citarum River, starting in Balekambang through the area of Bandung Regency to the downstream village of Nanjung, where the river is dammed. Similar samples were also collected from seven tributaries of the Citarum River. Magnetic and heavy metal analyses show that unlike river sediments from a non-volcanic catchment area in temperate climates, magnetic susceptibility values tend to decrease downstream, showing that the magnetic minerals in the upstream area are mostly lithogenic in origin, containing more Fe-bearing minerals compared to those in tributary samples which are anthropogenic in origin. Anthropogenic pollution is also represented by the increase of Zn content along the river. The results suggest that applying magnetic methods for monitoring river pollution in the tropics or in the volcanic areas should be carefully analyzed and interpreted.
- Published
- 2017
36. Lithogenic and Anthropogenic Components in Surface Sediments from Lake Limboto as Shown by Magnetic Mineral Characteristics, Trace Metals, and REE Geochemistry
- Author
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Yunginger, Raghel, primary, Bijaksana, Satria, additional, Dahrin, Darharta, additional, Zulaikah, Siti, additional, Hafidz, Abd, additional, Kirana, Kartika, additional, Sudarningsih, Sudarningsih, additional, Mariyanto, Mariyanto, additional, and Fajar, Silvia, additional
- Published
- 2018
- Full Text
- View/download PDF
37. Lithogenic and Anthropogenic Components in Surface Sediments from Lake Limboto as Shown by Magnetic Mineral Characteristics, Trace Metals, and REE Geochemistry
- Author
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Mariyanto Mariyanto, Kartika Hajar Kirana, Satria Bijaksana, Raghel Yunginger, Siti Zulaikah, Darharta Dahrin, Silvia Jannatul Fajar, Abd Hafidz, and Sudarningsih Sudarningsih
- Subjects
Mineral ,Rare-earth element ,lcsh:QE1-996.5 ,trace metals ,Geochemistry ,Sediment ,rare earth elements ,magnetic minerals ,lithogenic ,010501 environmental sciences ,Sedimentation ,010502 geochemistry & geophysics ,01 natural sciences ,Magnetic susceptibility ,anthropogenic ,lcsh:Geology ,surface sediment ,Population pressure ,Lake Limboto ,Remanence ,General Earth and Planetary Sciences ,Environmental science ,Saturation (chemistry) ,0105 earth and related environmental sciences - Abstract
Lake Limboto is one of the major lakes in Sulawesi, Indonesia. It is currently undergoing serious degradation due to population pressure. As more residential areas have been established around the lake, the sedimentation rate has increased because of the contribution of anthropogenic particles. In this study, the lithogenic and anthropogenic components in surface sediments from 17 points in the lake were studied and identified using a combination of magnetic and geochemical analyses. The results showed that although the magnetic susceptibility values in R (residential) and NR (non-residential) areas were relatively similar, the values of saturation isothermal remanent magnetization (SIRM) as well as those of SIRM/χLF differed significantly, implying that the magnetic characteristics of the lithogenic component (in the NR area) differ from those of the anthropogenic component (in the R area). The discrepancy between the anthropogenic and lithogenic contributions was further supported by trace metals and rare earth element (REE) contents. Sediment samples in the R area contained higher levels of Mn, La, Pr, and Gd, while in the NR area they contained higher levels of Fe, Sc, Nd, and Ce. The magnetic susceptibility also correlated strongly with Fe, Cu, Zn, and Mn contents in the NR area. A similar correlation was not observed in the R area. The results above imply that a combination of magnetic and geochemical analyses can successfully differentiate lithogenic and anthropogenic components or contributions in lake sediments.
- Published
- 2018
38. Hotelling T2 Control Chart for Detecting Changes in Mortality Models Based on Machine-Learning Decision Tree
- Author
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Suryo Adi Rakhmawan, M. Hafidz Omar, Muhammad Riaz, and Nasir Abbas
- Subjects
mortality modelling ,Lee–Carter model ,control chart ,Hotelling T2 ,machine learning ,Mathematics ,QA1-939 - Abstract
Mortality modelling is a practical method for the government and various fields to obtain a picture of mortality up to a specific age for a particular year. However, some information on the phenomenon may remain in the residual vector and be unrevealed from the models. We handle this issue by employing a multivariate control chart to discover substantial cohort changes in mortality behavior that the models still need to address. The Hotelling T2 control chart is applied to the externally studentized deviance model, which is already optimized using a machine-learning decision tree. This study shows a mortality model with the lowest MSE, MAPE, and deviance, by accomplishing simulations in various countries. In addition, the model that is more sensitive in detecting signals on the control chart is singled out so that we can perform a decomposition to determine the attributes of death in the specific outlying age group in a particular year. The case study in the decomposition uses data from the country Saudi Arabia. The overall results demonstrate that our method of processing and producing mortality models with machine learning can be a solution for developing countries or countries with limited mortality data to produce accurate predictions through monitoring control charts.
- Published
- 2023
- Full Text
- View/download PDF
39. Isotopic Tracer for Absolute Quantification of Metabolites of the Pentose Phosphate Pathway in Bacteria
- Author
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Khairunnisa Mohd Kamal, Mohd Hafidz Mahamad Maifiah, Yan Zhu, Nusaibah Abdul Rahim, Yumi Zuhanis Has-Yun Hashim, and Muhamad Shirwan Abdullah Sani
- Subjects
metabolomic ,bacterial metabolomics ,pentose phosphate pathway (PPP) ,isotope labeling ,absolute quantification ,Microbiology ,QR1-502 - Abstract
The pentose phosphate pathway (PPP) plays a key role in many metabolic functions, including the generation of NADPH, biosynthesis of nucleotides, and carbon homeostasis. In particular, the intermediates of PPP have been found to be significantly perturbed in bacterial metabolomic studies. Nonetheless, detailed analysis to gain mechanistic information of PPP metabolism remains limited as most studies are unable to report on the absolute levels of the metabolites. Absolute quantification of metabolites is a prerequisite to study the details of fluxes and its regulations. Isotope tracer or labeling studies are conducted in vivo and in vitro and have significantly improved the analysis and understanding of PPP. Due to the laborious procedure and limitations in the in vivo method, an in vitro approach known as Group Specific Internal Standard Technology (GSIST) has been successfully developed to measure the absolute levels of central carbon metabolism, including PPP. The technique adopts derivatization of an experimental sample and a corresponding internal standard with isotope-coded reagents to provide better precision for accurate identification and absolute quantification. In this review, we highlight bacterial studies that employed isotopic tracers as the tagging agents used for the absolute quantification analysis of PPP metabolites.
- Published
- 2022
- Full Text
- View/download PDF
40. Fabrication and Characterisation of MWCNT/Polyvinyl (PVC) Polymer Inclusion Membrane for Zinc (II) Ion Removal from Aqueous Solution
- Author
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Nadia Aqilah Khalid, Noor Fazliani Shoparwe, Abdul Hafidz Yusoff, Ahmad Ziad Sulaiman, Abdul Latif Ahmad, and Nur Aina Azmi
- Subjects
polymer inclusion membrane ,multiwalled-carbon nanotubes ,bis-(2-ethylhexyl) phosphate ,zinc (II) ions ,extraction ,adsorption ,Chemical technology ,TP1-1185 ,Chemical engineering ,TP155-156 - Abstract
Heavy metal pollution has prompted researchers to establish the most effective method to tackle the impacts of heavy metals on living things and the environment, which include by applying nanoparticles. An example is the employment of multi-walled carbon nanotubes (MWCNTs) as an additive in an intermediate membrane or polymer inclusion membrane (PIM). The MWCNTs were added to enhance the properties and reinforce the transport performance of zinc (II) ion (Zn2+) removal from the source phase to the receiver phase by the PIMs. The present study constructed a membrane with a poly(vinyl chloride) (PVC)-based polymer, dioctyl phthalate (DOP) plasticiser, and bis-(2-ethylhexyl) phosphate (B2EHP) carrier incorporated with different concentrations of MWCNTs. The contact angle (CA), water uptake, ion exchange capacity (IEC), and porosity of the fabricated membranes were evaluated. The membrane was also characterised by employing scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and electrochemical impedance spectroscopy (EIS). Subsequently, the fabricated PIM (W1) and mixed matrix (MM)-PIM (W2–W5) samples were assessed under different parameters to acquire the ideal membrane composition and effectiveness. Kinetic modelling of Zn2+ removal by the fabricated PIMs under similar conditions was performed to reveal the mechanisms involved. The average removal efficiency of the membranes was >99% at different parameter conditions. Nevertheless, the W3 membrane with 1.0 wt% MWCNT immersed in a 5 mg/L initial Zn2+ concentration and 1.0 M receiver solution for seven hours at pH 2 demonstrated the highest percentage of Zn2+ removal. The experimental data were best fitted to the pseudo-first-order kinetic model (PFO) in kinetic modelling, and the permeability and flux of the W3 at optimum conditions were 0.053 m s−1 and 0.0532 mol m−2 s−1, respectively. In conclusion, the transport mechanism of Zn2+ was enhanced with the addition of the MWCNTs.
- Published
- 2022
- Full Text
- View/download PDF
41. Effect of Stability of Two-Dimensional (2D) Aminoethyl Methacrylate Perovskite Using Lead-Based Materials for Ammonia Gas Sensor Application
- Author
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Muhamad Yuzaini Azrai Mat Yunin, Norfatihah Mohd Adenam, Wan M. Khairul, Abdul Hafidz Yusoff, and Hasyiya Karimah Adli
- Subjects
lead-based perovskite ,one-step sequential reaction ,material stability ,gas sensor ,Organic chemistry ,QD241-441 - Abstract
Changes in physical properties of (H2C=C(CH3)CO2CH2CH2NH3)2PbI2Cl2 and (H2C=C(CH3)CO2CH2CH2NH3)2Pb(NO3)2Cl2 (2D) perovskite materials from iodide-based (I-AMP) and nitrate-based (N-AMP) leads were investigated at different durations (days) for various storage conditions. UV-Vis spectra of both samples showed an absorption band of around λmax 420 nm due to the transition of n to π* of ethylene (C=C) and amine (NH2). XRD perovskite peaks could be observed at approximately 25.35° (I-AMP) and 23.1° (N-AMP). However, a major shift in I-AMP and dramatic changes in the crystallite size, FHWM and crystallinity percentage highlighted the instability of the iodide-based material. In contrast, N-AMP showed superior stability with 96.76% crystallinity even at D20 under the S condition. Both materials were exposed to ammonia (NH3) gas, and a new XRD peak of ammonium lead iodide (NH4PbI3) with a red-shifted perovskite peak (101) was observed for the case of I-AMP. Based on the FWHM, crystallite size, crystallinity and lattice strain analysis, it can be concluded N-AMP’s stability was maintained even after a few days of exposure to the said gases. These novel nitrate-based lead perovskite materials exhibited great potential for stable perovskite 2D materials and recorded less toxicity compared to famous lead iodide (PbI2) material.
- Published
- 2022
- Full Text
- View/download PDF
42. Application of General Full Factorial Statistical Experimental Design’s Approach for the Development of Sustainable Clay-Based Ceramics Incorporated with Malaysia’s Electric Arc Furnace Steel Slag Waste
- Author
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Pao Ter Teo, Siti Koriah Zakaria, Nurulakmal Mohd Sharif, Anasyida Abu Seman, Mustaffa Ali Azhar Taib, Julie Juliewatty Mohamed, Mahani Yusoff, Abdul Hafidz Yusoff, Mardawani Mohamad, Arlina Ali, and Mohamad Najmi Masri
- Subjects
general full factorial design (GFFD) ,electric arc furnace (EAF) steel slag waste ,sustainable clay-based ceramics ,Crystallography ,QD901-999 - Abstract
This study aims to optimize the composition (body formulation) and firing temperature of sustainable ceramic clay-based ceramics incorporated with electric arc furnace (EAF) steel slag waste using general full factorial design (GFFD). The optimization is necessary to minimize drawbacks of high iron oxide’s fluxing agent (originated from electric arc furnace, EAF steel slag waste), which led to severe surface defects and high closed porosity issue of the ceramics. Statistical analysis of GFFD including model adequacy checking, analysis of variance (ANOVA), interaction plots, regression model, contour plot and response optimizer were conducted in the study. The responses (final properties of ceramics) investigated were firing shrinkage, water absorption, apparent porosity, bulk density and modulus of rupture (MOR). Meanwhile, the factors employed in experimental parameters were weight percentage (wt.%) of EAF slag added and firing temperature. Upon statistical analysis, GFFD has deduced that wt.% amount of EAF slag added and firing temperatures are proven to significantly influence the final properties of the clay-based ceramic incorporated with EAF slag. The results of conducted statistical analysis were also highly significant and proven valid for the ceramics. Optimized properties (maximum MOR, minimum water absorption and apparent porosity) of the ceramic were attained at 50 wt.% of EAF slag added and firing temperature of 1180 °C.
- Published
- 2021
- Full Text
- View/download PDF
43. A Review on Haematococcus pluvialis Bioprocess Optimization of Green and Red Stage Culture Conditions for the Production of Natural Astaxanthin
- Author
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Siti Nur Hazwani Oslan, Noor Fazliani Shoparwe, Abdul Hafidz Yusoff, Ainihayati Abdul Rahim, Chang Shen Chang, Joo Shun Tan, Siti Nurbaya Oslan, Kavithraashree Arumugam, Arbakariya Bin Ariff, Ahmad Ziad Sulaiman, and Mohd Shamzi Mohamed
- Subjects
natural secondary carotenoid ,Haematococcus pluvialis ,astaxanthin ,microalgae ,bioprocess optimization ,Microbiology ,QR1-502 - Abstract
As the most recognizable natural secondary carotenoid astaxanthin producer, the green microalga Haematococcus pluvialis cultivation is performed via a two-stage process. The first is dedicated to biomass accumulation under growth-favoring conditions (green stage), and the second stage is for astaxanthin evolution under various stress conditions (red stage). This mini-review discusses the further improvement made on astaxanthin production by providing an overview of recent works on H. pluvialis, including the valuable ideas for bioprocess optimization on cell growth, and the current stress-exerting strategies for astaxanthin pigment production. The effects of nutrient constituents, especially nitrogen and carbon sources, and illumination intensity are emphasized during the green stage. On the other hand, the significance of the nitrogen depletion strategy and other exogenous factors comprising salinity, illumination, and temperature are considered for the astaxanthin inducement during the red stage. In short, any factor that interferes with the cellular processes that limit the growth or photosynthesis in the green stage could trigger the encystment process and astaxanthin formation during the red stage. This review provides an insight regarding the parameters involved in bioprocess optimization for high-value astaxanthin biosynthesis from H. pluvialis.
- Published
- 2021
- Full Text
- View/download PDF
44. Assessment of Electric Arc Furnace (EAF) Steel Slag Waste’s Recycling Options into Value Added Green Products: A Review
- Author
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Pao Ter Teo, Siti Koriah Zakaria, Siti Zuliana Salleh, Mustaffa Ali Azhar Taib, Nurulakmal Mohd Sharif, Anasyida Abu Seman, Julie Juliewatty Mohamed, Mahani Yusoff, Abdul Hafidz Yusoff, Mardawani Mohamad, Mohamad Najmi Masri, and Sarizam Mamat
- Subjects
EAF steel slag ,Malaysian steelmaking industry ,recycle options of EAF slag ,Mining engineering. Metallurgy ,TN1-997 - Abstract
Steel slag is one of the most common waste products from the steelmaking industry. Conventional methods of slag disposal can cause negative impacts on humans and the environment. In this paper, the process of steel and steel slag production, physical and chemical properties, and potential options of slag recycling were reviewed. Since steel is mainly produced through an electric arc furnace (EAF) in Malaysia, most of the recycling options reviewed in this paper focused on EAF slag and the strengths and weaknesses of each recycle option were outlined. Based on the reports from previous studies, it was found that only a portion of EAF slag is recycled into more straightforward, but lower added value applications such as aggregates for the construction industry and filter/absorber for wastewater treatments. On the other hand, higher added value recycling options for EAF slag that are more complicated such as incorporated as raw material for Portland cement and ceramic building materials remain at the laboratory testing stage. The main hurdle preventing EAF slag from being incorporated as a raw material for higher added value industrial applications is its inconsistent chemical composition. The chemical composition of EAF slag can vary based on the scrap metal used for steel production. For this, mineral separation techniques can be introduced to classify the EAF slag base on its physical and chemical compositions. We concluded that future research on recycling EAF slag should focus on separation techniques that diversify the recycling options for EAF slag, thereby increasing the waste product’s recycling rate.
- Published
- 2020
- Full Text
- View/download PDF
45. Resorcinol-Formaldehyde (RF) as a Novel Plasticizer for Starch-Based Solid Biopolymer Electrolyte
- Author
-
Vidhya Selvanathan, Mohd Hafidz Ruslan, Mohammod Aminuzzaman, Ghulam Muhammad, N. Amin, Kamaruzzaman Sopian, and Md. Akhtaruzzaman
- Subjects
starch ,resorcinol-formaldehyde ,polymer electrolyte ,ionic conductivity ,lithium triflate ,plasticization ,Organic chemistry ,QD241-441 - Abstract
A starch-resorcinol-formaldehyde (RF)-lithium triflate (LiTf) based biodegradable polymer electrolyte membrane was synthesized via the solution casting technique. The formation of RF crosslinks in the starch matrix was found to repress the starch’s crystallinity as indicated by the XRD data. Incorporation of the RF plasticizer improved the conductivity greatly, with the highest room-temperature conductivity recorded being 4.29 × 10−4 S cm−1 achieved by the starch:LiTf:RF (20 wt.%:20 wt.%:60 wt.%) composition. The enhancement in ionic conductivity was an implication of the increase in the polymeric amorphous region concurrent with the suppression of the starch’s crystallinity. Chemical complexation between the plasticizer, starch, and lithium salt components in the electrolyte was confirmed by FTIR spectra.
- Published
- 2020
- Full Text
- View/download PDF
46. Organosoluble Starch-Cellulose Binary Polymer Blend as a Quasi-Solid Electrolyte in a Dye-Sensitized Solar Cell
- Author
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Vidhya Selvanathan, Rosiyah Yahya, Mohd Hafidz Ruslan, Kamaruzzaman Sopian, Nowshad Amin, Majid Nour, Hatem Sindi, Muhyaddin Rawa, and Md. Akhtaruzzaman
- Subjects
phthaloyl starch ,hydroxyethyl cellulose ,rheology ,quasi-solid electrolyte ,dye-sensitized solar cell ,Organic chemistry ,QD241-441 - Abstract
This work is a pioneer attempt to fabricate quasi-solid dye-sensitized solar cell (QSDDSC) based on organosoluble starch derivative. Rheological characterizations of the PhSt-HEC blend based gels exhibited viscoelastic properties favorable for electrolyte fabrication. From amplitude sweep and tack test analyses, it was evident that the inclusion of LiI improved the rigidity and tack property of the gels. On the other hand, the opposite was true for TPAI based gels, which resulted in less rigid and tacky electrolytes. The crystallinity of the gels was found to decline with increasing amount of salt in both systems. The highest photoconversion efficiency of 3.94% was recorded upon addition of 12.5 wt % TPAI and this value is one of the highest DSSC performance recorded for starch based electrolytes. From electrochemical impedance spectroscopy (EIS), it is deduced that the steric hindrance imposed by bulky cations aids in hindering recombination between photoanode and electrolyte.
- Published
- 2020
- Full Text
- View/download PDF
47. Dual Stratified Nanofluid Flow Past a Permeable Shrinking/Stretching Sheet Using a Non-Fourier Energy Model
- Author
-
Najiyah Safwa Khashi’ie, Norihan Md Arifin, Ezad Hafidz Hafidzuddin, and Nadihah Wahi
- Subjects
nanofluid ,non-fourier energy ,suction ,stratification ,stability analysis ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
The present study emphasizes the combined effects of double stratification and buoyancy forces on nanofluid flow past a shrinking/stretching surface. A permeable sheet is used to give way for possible wall fluid suction while the magnetic field is imposed normal to the sheet. The governing boundary layer with non-Fourier energy equations (partial differential equations (PDEs)) are converted into a set of nonlinear ordinary differential equations (ODEs) using similarity transformations. The approximate relative error between present results (using the boundary value problem with fourth order accuracy (bvp4c) function) and previous studies in few limiting cases is sufficiently small (0% to 0.3694%). Numerical solutions are graphically displayed for several physical parameters namely suction, magnetic, thermal relaxation, thermal and solutal stratifications on the velocity, temperature and nanoparticles volume fraction profiles. The non-Fourier energy equation gives a different estimation of heat and mass transfer rates as compared to the classical energy equation. The heat transfer rate approximately elevates 5.83% to 12.13% when the thermal relaxation parameter is added for both shrinking and stretching cases. Adversely, the mass transfer rate declines within the range of 1.02% to 2.42%. It is also evident in the present work that the augmentation of suitable wall mass suction will generate dual solutions. The existence of two solutions (first and second) are noticed in all the profiles as well as the local skin friction, Nusselt number and Sherwood number graphs within the considerable range of parameters. The implementation of stability analysis asserts that the first solution is the real solution.
- Published
- 2019
- Full Text
- View/download PDF
48. A Stability Analysis for Magnetohydrodynamics Stagnation Point Flow with Zero Nanoparticles Flux Condition and Anisotropic Slip
- Author
-
Najiyah Safwa Khashi’ie, Norihan Md Arifin, Roslinda Nazar, Ezad Hafidz Hafidzuddin, Nadihah Wahi, and Ioan Pop
- Subjects
nanofluid ,stagnation sheet ,three-dimensional flow ,slip condition ,stability analysis ,Technology - Abstract
The numerical study of nanofluid stagnation point flow coupled with heat and mass transfer on a moving sheet with bi-directional slip velocities is emphasized. A magnetic field is considered normal to the moving sheet. Buongiorno’s model is utilized to assimilate the mixed effects of thermophoresis and Brownian motion due to the nanoparticles. Zero nanoparticles’ flux condition at the surface is employed, which indicates that the nanoparticles’ fraction are passively controlled. This condition makes the model more practical for certain engineering applications. The continuity, momentum, energy and concentration equations are transformed into a set of nonlinear ordinary (similarity) differential equations. Using bvp4c code in MATLAB software, the similarity solutions are graphically demonstrated for considerable parameters such as thermophoresis, Brownian motion and slips on the velocity, nanoparticles volume fraction and temperature profiles. The rate of heat transfer is reduced with the intensification of the anisotropic slip (difference of two-directional slip velocities) and the thermophoresis parameter, while the opposite result is obtained for the mass transfer rate. The study also revealed the existence of non-unique solutions on all the profiles, but, surprisingly, dual solutions exist boundlessly for any positive value of the control parameters. A stability analysis is implemented to assert the reliability and acceptability of the first solution as the physical solution.
- Published
- 2019
- Full Text
- View/download PDF
49. Lithogenic and Anthropogenic Components in Surface Sediments from Lake Limboto as Shown by Magnetic Mineral Characteristics, Trace Metals, and REE Geochemistry
- Author
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Raghel Yunginger, Satria Bijaksana, Darharta Dahrin, Siti Zulaikah, Abd Hafidz, Kartika Hajar Kirana, Sudarningsih Sudarningsih, Mariyanto Mariyanto, and Silvia Jannatul Fajar
- Subjects
lithogenic ,anthropogenic ,Lake Limboto ,magnetic minerals ,trace metals ,rare earth elements ,surface sediment ,Geology ,QE1-996.5 - Abstract
Lake Limboto is one of the major lakes in Sulawesi, Indonesia. It is currently undergoing serious degradation due to population pressure. As more residential areas have been established around the lake, the sedimentation rate has increased because of the contribution of anthropogenic particles. In this study, the lithogenic and anthropogenic components in surface sediments from 17 points in the lake were studied and identified using a combination of magnetic and geochemical analyses. The results showed that although the magnetic susceptibility values in R (residential) and NR (non-residential) areas were relatively similar, the values of saturation isothermal remanent magnetization (SIRM) as well as those of SIRM/χLF differed significantly, implying that the magnetic characteristics of the lithogenic component (in the NR area) differ from those of the anthropogenic component (in the R area). The discrepancy between the anthropogenic and lithogenic contributions was further supported by trace metals and rare earth element (REE) contents. Sediment samples in the R area contained higher levels of Mn, La, Pr, and Gd, while in the NR area they contained higher levels of Fe, Sc, Nd, and Ce. The magnetic susceptibility also correlated strongly with Fe, Cu, Zn, and Mn contents in the NR area. A similar correlation was not observed in the R area. The results above imply that a combination of magnetic and geochemical analyses can successfully differentiate lithogenic and anthropogenic components or contributions in lake sediments.
- Published
- 2018
- Full Text
- View/download PDF
50. Variations in the Concentration of Magnetic Minerals and Heavy Metals in Suspended Sediments from Citarum River and Its Tributaries, West Java, Indonesia
- Author
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Sudarningsih Sudarningsih, Satria Bijaksana, Rizky Ramdani, Abd Hafidz, Aditya Pratama, Widodo Widodo, Irwan Iskandar, Darharta Dahrin, Silvia Jannatul Fajar, and Nono Agus Santoso
- Subjects
Citarum River ,volcanic area ,magnetic method ,magnetic susceptibility ,Zn content ,West Java ,heavy metal pollution ,tropical climate conditions ,Geology ,QE1-996.5 - Abstract
The Citarum River has a volcanic catchment area in West Java Province, and is one of the nationally strategic rivers in tropical Indonesia due to its roles in water supply and in power generation. The river is economically important, but it is also polluted by industrial, agricultural, and residential wastes. Suspended sediment samples were collected along a certain section of the Citarum River, starting in Balekambang through the area of Bandung Regency to the downstream village of Nanjung, where the river is dammed. Similar samples were also collected from seven tributaries of the Citarum River. Magnetic and heavy metal analyses show that unlike river sediments from a non-volcanic catchment area in temperate climates, magnetic susceptibility values tend to decrease downstream, showing that the magnetic minerals in the upstream area are mostly lithogenic in origin, containing more Fe-bearing minerals compared to those in tributary samples which are anthropogenic in origin. Anthropogenic pollution is also represented by the increase of Zn content along the river. The results suggest that applying magnetic methods for monitoring river pollution in the tropics or in the volcanic areas should be carefully analyzed and interpreted.
- Published
- 2017
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