Magnetic circuit optimization in designing Magnetorheological damper

Yazid, Izyan I.M.,Mazlan, Saiful A.,Kikuchi, Takehito,Zamzuri, Hairi,Imaduddin, Fitrian Techno-Press 2014 Smart Structures and Systems, An International Jou Vol.14 No.5

This paper presents the materials analysis for combination of working modes of Magnetorheological (MR) damper. The materials were selected based on the optimum magnetic field strength at the effective areas in order to obtain a better design of MR damper. The design of electromagnetic circuit is one of the critical criteria in designing MR dampers besides the working mechanism and the types of MR damper. The increase in the magnetic field strength is an indication of the improvement in the damping performance of the MR damper. Eventually, the experimental test was performed under quasi-static loading to observe the performances of MR damper in shear mode, squeeze mode and mixed mode. The results showed that the increment of forces was obtained with the increased current due to higher magnetic flux density generated by electromagnetic coils. In general, it can be summarized that the combination of modes generates higher forces than single mode for the same experimental parameters throughout the study.

The Effect of Ethnicity on Wideband Absorbance of Neonates with Healthy Middle Ear Functions in Malaysia: A Preliminary Study

Hamzah A Wali,Rafidah Mazlan 대한청각학회 2018 Journal of Audiology & Otology Vol.22 No.1

Background and Objectives: Although ethnicity effect on wideband absorbance (WBA) findingswas evident for adults, its effect on neonates has not been established yet. This studyaimed to investigate the influence of ethnicity on WBA measured at 0 daPa from neonateswith healthy middle ear functions. Subjects and Methods: Participants were 99 normal,healthy, full-term newborn babies with chronological age between 11 and 128 hours of age(mean=46.73, standard deviation=26.36). A cross-sectional study design was used to measureWBA at 16 one-third octave frequency points from 99 neonates comprising of threeethnic groups: Malays (n=58), Chinese (n=13) and Indians (n=28). A total of 165 ears (83.3%)that passed a battery of tests involving distortion product otoacoustic emissions, 1 kHztympanometry and acoustic stapedial reflex were further tested using WBA. Moreover, bodysize measurements were recorded from each participant. Results: The Malays and Indiansneonates showed almost identical WBA response across the frequency range while the Chinesebabies showed lower absorbance values between 1.25 kHz and 5 kHz. However, thedifferences observed in WBA between the three ethnic groups were not statistically significant(p=0.23). Additionally, there were no statistically significant difference in birth weight,height and head circumference among the three ethnic groups. Conclusions: This studyshowed that Malays, Chinese and Indians neonates were not significantly different in their WBAresponses. In conclusion, to apply for the ethnic-specific norms is not warranted when testingneonates from population constitute of these three ethnicities.

Simulation study of magnetorheological testing cell design by incorporating all basic operating modes

Mughni, Mohd J.,Mazlan, Saiful A.,Zamzuri, Hairi,Yazid, Izyan I.M.,Rahman, Mohd A.A. Techno-Press 2014 Smart Structures and Systems, An International Jou Vol.14 No.5

Magnetorheological (MR) fluid is one of the field-responsive fluids that is of interest to many researchers due to its high yield stress value, which depends on the magnetic field strength. Similar to electrorheological (ER) fluid, the combination of working modes is one of the techniques to increase the performance of the fluids with limited focus on MR fluids. In this paper, a novel MR testing cell incorporated with valve, shear and squeeze operational modes is designed and constructed in order to investigate the behaviour of MR fluid in combined mode. The magnetic field distribution in the design concept was analyzed using finite element method in order to verify the effective areas of each mode have the acceptable range of flux density. The annular gap of valve and shear were fixed at 1 mm, while the squeeze gap between the parallel circular surfaces was varied up to 20 mm. Three different coil configurations, which were made up from 23 SWG copper wires were set up in the MR cell. The simulation results indicated that the magnetic field distributed in the squeeze gap was the highest among the other gaps with all coils were subjected to a constant applied current of 1 A. Moreover, the magnetic flux densities in all gaps were in a good range of magnitude based on the simulations that validated the proposed design concept. Hence, the 3D model of the MR testing cell was designed using Solidworks for manufacturing processes.

Is Finance-Growth Nexus Linear in Selected Countries of Middle East and Northern Africa?

Daouia Chebab,Nur Syazwani Mazlan,Wan Azman Saini Wan Ngah,Lee Chin 세종대학교 경제통합연구소 2020 Journal of Economic Integration Vol.35 No.2

The present study re-examines the impact of financial development on economic growth in resource-rich Middle East and North Africa (MENA) countries over 1987-2015. Although several studies investigate the finance-growth nexus, none emphasized the nature of this relationship in MENA. In the long run, an inverted U-shaped association between finance and growth is indicated when using pooled mean group estimations. However, the relationship is not significant in the short run. The outcomes suggest that financial development is significantly and positively affiliated with economic growth up to a certain level. After this turning point, additional financial development tends to adversely affect economic growth. The existence of an inverse U-shape association between financial development and economic growth was confirmed by the estimation of the U-test. The outcomes of our study are important to policymakers, in terms of optimizing the necessary and limit of financial development to ensure maximum benefit for the whole economy through the banking sector.

How Effective is the New Generation of GPM Satellite Precipitation in Characterizing the Rainfall Variability over Malaysia?

Mohd Rizaludin Mahmud,Mazlan Hashim,Mohd Nadzri Mohd Reba 한국기상학회 2017 Asia-Pacific Journal of Atmospheric Sciences Vol.53 No.3

We investigated the potential of the new generation of satellite precipitation product from the Global Precipitation Mission (GPM) to characterize the rainfall in Malaysia. Most satellite precipitation products have limited ability to precisely characterize the high dynamic rainfall variation that occurred at both time and scale in this humid tropical region due to the coarse grid size to meet the physical condition of the smaller land size, sub-continent and islands. Prior to the status quo, an improved satellite precipitation was required to accurately measure the rainfall and its distribution. Subsequently, the newly released of GPM precipitation product at half-hourly and 0.1o resolution served an opportunity to anticipate the aforementioned conflict. Nevertheless, related evidence was not found and therefore, this study made an initiative to fill the gap. A total of 843 rain gauges over east (Borneo) and west Malaysia (Peninsular) were used to evaluate the rainfall the GPM rainfall data. The assessment covered all critical rainy seasons which associated with Asian Monsoon including northeast (Nov. - Feb.), southwest (May - Aug.) and their subsequent inter-monsoon period (Mar. - Apr. & Sep. - Oct.). The ability of GPM to provide quantitative rainfall estimates and qualitative spatial rainfall patterns were analysed. Our results showed that the GPM had good capacity to depict the spatial rainfall patterns in less heterogeneous rainfall patterns (Spearman’s correlation, 0.591 to 0.891) compared to the clustered one (r = 0.368 to 0.721). Rainfall intensity and spatial heterogeneity that is largely driven by seasonal monsoon has significant influence on GPM ability to resolve local rainfall patterns. In quantitative rainfall estimation, large errors can be primarily associated with the rainfall intensity increment. 77% of the error variation can be explained through rainfall intensity particularly the high intensity (> 35 mm d−1). A strong relationship between GPM rainfall and error was found from heavy (~35 mm d−1) to violent rain (160 mm d−1). The output of this study provides reference regarding the performance of GPM data for respective hydrology studies in this region.

Understanding the Sentiment on Gig Economy: Good or Bad?

NORAZMI, Fatin Aimi Naemah,MAZLAN, Nur Syazwani,SAID, Rusmawati,OK RAHMAT, Rahmita Wirza Korea Distribution Science Association 2022 The Journal of Asian Finance, Economics and Busine Vol.9 No.10

The gig economy offers many advantages, such as flexibility, variety, independence, and lower cost. However, there are also safety concerns, lack of regulations, uncertainty, and unsatisfactory services, causing people to voice their opinion on social media. This paper aims to explore the sentiments of consumers concerning gig economy services (Grab, Foodpanda and Airbnb) through the analysis of social media. First, Vader Lexicon was used to classify the comments into positive, negative, and neutral sentiments. Then, the comments were further classified into three machine learning algorithms: Support Vector Machine, Light Gradient Boosted Machine, and Logistic Regression. Results suggested that gig economy services in Malaysia received more positive sentiments (52%) than negative sentiments (19%) and neutral sentiments (29%). Based on the three algorithms used in this research, LGBM has been the best model with the highest accuracy of 85%, while SVM has 84% and LR 82%. The results of this study proved the power of text mining and sentiment analysis in extracting business value and providing insight to businesses. Additionally, it aids gig managers and service providers in understanding clients' sentiments about their goods and services and making necessary adjustments to optimize satisfaction.

Analysing NOx and soot formations of an annular chamber with various types of biofuels

Joanne Zi Fen, Lim,Nurul Musfirah, Mazlan Techno-Press 2022 Advances in aircraft and spacecraft science Vol.9 No.6

The rapid decrease of fossil fuel resources and increase of environmental pollution caused by aviation industries have become a severe issue which leads to an increase in the greenhouse effect. The use of biofuel becomes an option to alleviate issues related to unrenewable resources. This study presents a computational simulation of the biofuel combustion characteristics of various alternative fuels in an annular combustion chamber designed for training aircraft. The biofuels used in this study are Sorghum Oil Methyl Ester (SOME), Spirulina Platensis Algae (SPA) and Camelina Hydrotreated Esters and Fatty Acids (CHEFA). Meanwhile, Jet-A is used as a baseline fuel. The fuel properties and combustion characteristics are being investigated and analysed. The results are presented in terms of temperature and pressure profiles in addition to the formation of NOx and soot generated from the combustion chamber. Results obtained show that CHEFA fuel is the most recommended biofuel among all four tested fuels as it is being found that it burns with 37.6% lower temperature, 15.2% lower pressure, 89.5% lower NOx emission and 8.1% lower soot emission compared with the baseline fuel in same combustion chamber geometry with same initial parameters.

Analysing NOx and soot formations of an annular chamber with various types of biofuels

Joanne Zi Fen, Lim,Nurul Musfirah, Mazlan Techno-Press 2022 Advances in aircraft and spacecraft science Vol.9 No.6

The rapid decrease of fossil fuel resources and increase of environmental pollution caused by aviation industries have become a severe issue which leads to an increase in the greenhouse effect. The use of biofuel becomes an option to alleviate issues related to unrenewable resources. This study presents a computational simulation of the biofuel combustion characteristics of various alternative fuels in an annular combustion chamber designed for training aircraft. The biofuels used in this study are Sorghum Oil Methyl Ester (SOME), Spirulina Platensis Algae (SPA) and Camelina Hydrotreated Esters and Fatty Acids (CHEFA). Meanwhile, Jet-A is used as a baseline fuel. The fuel properties and combustion characteristics are being investigated and analysed. The results are presented in terms of temperature and pressure profiles in addition to the formation of NOx and soot generated from the combustion chamber. Results obtained show that CHEFA fuel is the most recommended biofuel among all four tested fuels as it is being found that it burns with 37.6% lower temperature, 15.2% lower pressure, 89.5% lower NOx emission and 8.1% lower soot emission compared with the baseline fuel in same combustion chamber geometry with same initial parameters.

Simulation study of magnetorheological testing cell design by incorporating all basic operating modes

Mohd J. Mughni,Saiful A. Mazlan,Izyan I.M. Yazid,Mohd A.A. Rahman,Hairi Zamzuri 국제구조공학회 2014 Smart Structures and Systems, An International Jou Vol.14 No.5

Magnetorheological (MR) fluid is one of the field-responsive fluids that is of interest to many researchers due to its high yield stress value, which depends on the magnetic field strength. Similar to electrorheological (ER) fluid, the combination of working modes is one of the techniques to increase the performance of the fluids with limited focus on MR fluids. In this paper, a novel MR testing cell incorporated with valve, shear and squeeze operational modes is designed and constructed in order to investigate the behaviour of MR fluid in combined mode. The magnetic field distribution in the design concept was analyzed using finite element method in order to verify the effective areas of each mode have the acceptable range of flux density. The annular gap of valve and shear were fixed at 1 mm, while the squeeze gap between the parallel circular surfaces was varied up to 20 mm. Three different coil configurations, which were made up from 23 SWG copper wires were set up in the MR cell. The simulation results indicated that the magnetic field distributed in the squeeze gap was the highest among the other gaps with all coils were subjected to a constant applied current of 1 A. Moreover, the magnetic flux densities in all gaps were in a good range of magnitude based on the simulations that validated the proposed design concept. Hence, the 3D model of the MR testing cell was designed using Solidworks for manufacturing processes.

Zero‑dimensional model for the prediction of carbon nanotube (CNT) growth region in heterogeneous methane‑flame environment

Muhammad Thalhah Zainal,Norikhwan Hamzah,Mazlan Abdul Wahid,Natrah Kamaruzaman,Cheng Tung Chong,Mohd Hanafi Ani,Shokri Amzin,Tarit Das,Mohd Fairus Mohd Yasin 한국탄소학회 2023 Carbon Letters Vol.33 No.7

The conventional multi-scale modelling approach that predicts carbon nanotube (CNT) growth region in heterogeneous flame environment is computationally exhaustive. Thus, the present study is the first attempt to develop a zero-dimensional model based on existing multi-scale model where mixture fraction z and the stoichiometric mixture fraction zst are employed to correlate burner operating conditions and CNT growth region for diffusion flames. Baseline flame models for inverse and normal diffusion flames are first established with satisfactory validation of the flame temperature and growth region prediction at various operating conditions. Prior to developing the correlation, investigation on the effects of zst on CNT growth region is carried out for 17 flame conditions with zst of 0.05 to 0.31. The developed correlation indicates linear ( zlb=1.54zst +0.11) and quadratic ( zhb=zst(7-13zst )) models for the zlb and zhb corresponding to the low and high boundaries of mixture fraction, respectively, where both parameters dictate the range of CNT growth rate (GR) in the mixture fraction space. Based on the developed correlations, the CNT growth in mixture fraction space is optimum in the flame with medium-range zst conditions between 0.15 and 0.25. The stronger relationship between growth-region mixture-fraction (GRMF) and zst at the near field region close to the flame sheet compared to that of the far field region away from the flame sheet is due to the higher temperature gradient at the former region compared to that of the latter region. The developed models also reveal three distinct regions that are early expansion, optimum, and reduction of GRMF at varying zst.