Mohd Aftar Abu Bakar

Universiti Kebangsaan Malaysia | ukm · School of Mathematical Sciences

Air pollution poses a significant threat to human health and the environment, especially in developing nations facing rapid industrialization, urbanization, and increased vehicle emissions. As cities and factories continue to grow, the air quality problem worsens, making it crucial to enhance the monitoring, testing, and forecasting of air quality....

The degradation models are often applied on the degradation data for studying time-to-failure distribution. In this study, the Bayesian approach is applied on the power degradation model for estimating the parameters of the time-to-failure distribution and its percentiles. Two different distributions are assumed for the degradation parameter of the...

Air pollution is a persistent issue that arises worldwide. Mitigating this issue poses a significant challenge due to endless industrialization activities, rising construction works and vehicle emissions on the road. Particulate matter (PM10) with an aerodynamic diameter of less than 10 µm is one of the primary pollutants that significantly impact...

This study delves into nocturnal air quality, focusing on carbon monoxide (CO), nitrogen dioxide (NO2), surface ozone (O3), and particulate matter (PM2.5), in contrasting areas of Banting, Selangor: the rural-industrial Olak Lempit and the rural Bukit Changgang. Employing AiRBOXSense, a rigorously calibrated low-cost sensor in Olak Lempit, alongsid...

Medical imaging is an essential element in healthcare, especially for the early diagnosis and treatment of illnesses, including breast cancer. Breast cancer is an illness with a high mortality rate that mostly affects women worldwide. Currently, histopathology image analysis is one of the rising research areas in cancer diagnosis. With digital imag...

This paper presents a new two-step approach for record linkage, focusing on the creation of high-quality training data in the first step. The approach employs the unsupervised random forest model as a similarity measure to produce a similarity score vector for record matching. Three constructions were proposed to select non-match pairs for the trai...

Following the rapid development of various industrial sectors, air pollution frequently occurs in every corner of the world. As a dominant pollutant in Malaysia, particulate matter PM 10 can cause highly detrimental effects on human health. This study aims to predict the daily average concentration of PM 10 based on the data collected from 60 air q...

In this paper, the Bayesian method which involves informative and weakly informative priors are considered to estimate the parameters and percentiles of the time to failure distribution. The parameters of the time to failure distribution and its percentiles are determined based on linear degradation model where the degradation parameter is assumed...

Hourly particulate matter time series data from eight air quality monitoring stations in Peninsular Malaysia were forecast by using the Convolutional Neural Network (CNN) algorithm. Instead of using the original time series, which are time-domain sequence data, this study used the time-frequency domain sequence data retrieved by wavelet transformat...

There are several times where Malaysia suffers from severe air pollution , especially the urban and industrial area. The air quality stations across the country monitor various variables of air pollutants including particulate matter such as PM 10. Due to harmful effects of pollution on human health and the environment , especially for extreme case...

The Maximum Product of Spacing (MPS) is an alternative parameter estimation method for the Maximum Likelihood Estimator (MLE), since the MLE may not exist in some circumstances. However, the MPS estimator still has some weaknesses despite being an alternative method. This is due to the variations in distance between data points, particularly with e...

Medical imaging is gaining significant attention in healthcare, including breast cancer. Breast cancer is the most common cancer-related death among women worldwide. Currently, histopathology image analysis is the clinical gold standard in cancer diagnosis. However, the manual process of microscopic examination involves laborious work and can be mi...

Kajian ini bertujuan untuk membina model kualiti udara untuk meramalkan kepekatan bahan pencemar udara di Malaysia. Kaedah peramalan yang dipilih dalam kajian ini adalah suatu teknik pembelajaran mendalam iaitu Rangkaian Perlingkaran Temporal (TCN). Set data yang digunakan adalah siri masa zarahan terampai bersaiz diameter lebih kecil atau sama den...

The generalized extreme value distribution (GEVD) and various extreme value distributions are commonly applied in air pollution, telecommunications, operational risk management, finance, insurance, material sciences, economics, and hydrology, among many other industries that deal with extreme events. Extreme value distributions (EVDs) typically lim...

Accidents involving heavy vehicles are of significant concern as it poses a higher risk of fatality to both heavy vehicle drivers and other road users. This study is carried out based on the heavy vehicle crash data of 2014, extracted from the MIROS Road Accident and Analysis and Database System (M-ROADS). The main objective of this study is to ide...

Air quality monitoring is important in the management of the environment and pollution. In this study, time series of PM10 from air quality monitoring stations in Malaysia were clustered based on similarity in terms of time series patterns. The identified clusters were analyzed to gain meaningful information regarding air quality patterns in Malays...

Malaysia often suffers from haze problems almost every year. Therefore, there is a need for good air quality forecasting model for monitoring and management purposes. In this study, the air quality model based on the Long Short-Term Memory Network (LSTM) and Auto-Regressive Integrated Moving Average (ARIMA) was developed. The prediction of the part...

This study investigates the wavelet-based system identification capabilities on determining the system nonlinearity based on the system impulse response function. Wavelet estimates of the instantaneous envelopes and instantaneous frequency are used to plot the system backbone curve. This wavelet estimate is then used to estimate the values of the p...

Globally, the COVID-19 pandemic has had both positive and negative impacts on humans and the environment. In general, a positive impact can be seen on the environment, especially in regard to air quality. This positive impact on air quality around the world is a result of movement control orders (MCO) or lockdowns, which were carried out to reduce...

Background and Purpose: Understanding factors which affect the level of family well-being is important as it contributes to effective decision making among the policymakers to improve the family lives as well as to strengthen the family institution. Accordingly, this line of research is gaining attention. This study develops an ordinal regression m...

Tree-based classification techniques were used to identify the crucial factors influencing the Malaysian family well-being. Data from the nationwide survey, conducted by the National Population and Family Development Board (NPFDB) of Malaysia in 2011 were used for the analysis. Two types of tree-based classification techniques, which are the decisi...

Music is said to play an important role in influencing emotions. This study aims to investigate the influence of music on the emotions and happiness of university students. The study has collected 356 songs which are commonly heard among students from a sample group consisting of 40 university students from the Department of Mathematical Sciences o...

In this paper, the Rama distribution (RD) is considered and a new model called extended Rama distribution (ERD) is suggested. The new model involves the sum of two independent Rama distributed random variables. The probability density function (pdf) and cumulative distribution function (cdf) for the new model are obtained and analyzed. It is found...

In this paper, the two-parameter Akash distribution is generalized to size-biased two-parameter Akash distribution (SBTPAD). A further modification to SBTPAD is introduced, creating the power size-biased two-parameter Akash distribution (PSBTPAD). Several statistical properties of PSBTPAD distribution are proved. These properties include the follow...

In this paper, the two-parameter Akash distribution is generalized to size-biased two-parameter Akash distribution (SBTPAD). A further modification to SBTPAD is introduced, creating the power size-biased two-parameter Akash distribution (PSBTPAD). Several statistical properties of PSBTPAD distribution are proved. These properties include the follow...

Background: Biogenic Volatile Organic Compounds (BVOCs) such as isoprene (C5H8) are ozone (O3) precursors that can be emitted at significant concentrations from the oil palm tree (Elaeis guineensis). Reactions involving BVOCs can lead to increased levels of surface O3 which can significantly impair air quality and cause crop damage. This study focus...

Storm-event analysis (SEA) is a method of extracting information from rainfall data by defining rainfall events as storm events. A profile-based model in SEA defines storm events using the interevent time definition (IETD), which is the minimum value between consecutive storms. Based on statistical hypothesis tests done on the difference of the ave...

Environmentally adverse conditions, poverty, and social status can result in healthcare vulnerability. This paper aims at explaining the health-related expenditure patterns and low-income households' (B40) characteristics in Malaysia, to identify the health vulnerability factors. Descriptive analysis and k-means clustering methods were employed to...

It is believed that the education quality increases in line with the knowledge and understanding of students' personality. The theory and techniques associated with measurement of skills, abilities, attitudes and psychological traits are studied under the field of psychometrics. The students' psychometric scores and their academic programme of choi...

An improved forecasting model by merging two different computational models in predicting future volatility was proposed. The model integrates wavelet and EGARCH model where the pre-processing activity based on wavelet transform is performed with de-noising technique to eliminate noise in observed signal. The denoised signal is then feed into EGARC...

The world is currently going through the COVID-19 pandemic which has caused hundreds of thousands of deaths in just a few months. Considering the need for lockdown measures, most countries, including Malaysia, have implemented ‘Movement Control Orders’ (MCOs) as a prevention step to reduce the deadly spread of this disease. Local and worldwide medi...

This work is copyrighted by Università del Salento, and is licensed under a Creative Commons Attribuzione-Non commerciale-Non opere derivate 3.0 Italia License. For more information see: http://creativecommons.org/licenses/by-nc-nd/3.0/it/ In this paper, a new extension of length-biased Suja distribution (LBSD) called power length-biased Suja distr...

Time series clustering technique was used in this study to categorize the locations in Peninsular Malaysia according to the similarity of rainfall distribution patterns. Daily rainfall time series data from 12 meteorological observation stations across Peninsular Malaysia have been considered for this study. Four dissimilarity measure methods were...

A better understanding on the behavior of stock markets and their co-movement is obliged for investors and a country to diversify their investment risk. This study looks at Malaysia’s Islamic and conventional stock market indices and their relationship through Continuous Wavelet Transform and Wavelet Coherent methods. The analysis shows that both s...

Isoprene (C5H8) plays an important role in the formation of surface ozone (O3) and the secondary organic aerosol (SOA) which contributed to the climate change. This study aims to determine hourly distribution of tropospheric isoprene over the Western Coast of Antarctic Peninsula (WCAP) during the Malaysian Antarctic Scientific Expedition Cruise 201...

In this current and recent decade, various data and information are actively collected. The problem with increasing data from year to year has made it difficult for people to make the right decision. This is because when data increased, the number of options to choose from will also increase. Therefore, recommendation systems are needed to address...

Twitter is a social media service which enable users to send and also received messages or post known as tweet. In the era of big data, one of the main source of data is from Twitter. However, this types of data usually are unstructured, massive and complicated to be analyzed. In this study, Twitter’s data from Malaysian users were collected for on...

Text clustering is a data mining technique that is becoming more important in present studies. Document clustering makes use of text clustering to divide documents according to the various topics. The choice of words in document clustering is important to ensure that the document can be classified correctly. Three different methods of clustering wh...

Intensity-duration-frequency (IDF) curves represent the relationship between storm intensity, storm duration and return period. The IDF curves available are mostly done by fitting series of annual maximum rainfall intensity to parametric distributions. However, the length of annual rainfall records, especially for small scaled data, are not always...

Selecting suitable distributions for rainfall data is usually subjective and complex since it requires decision-makers to consider results from various measures of goodness-of-fit indices. In this study, the VIKOR method in multi-criteria decision-making analysis is modified to select the most suitable plotting positions to represent extreme storm...

Palm oil is deemed as one of the most important commodity that forms the economic backbone of Malaysia. Modeling and forecasting the daily price of palm oil is of great interest for Malaysia's economic growth. In this study, time series ARIMA models are used to fit the daily price of palm oil. The Akaike Infromation Criterion (AIC), Akaike Inf...

A model for a oscillating flap wave energy converter (WEC) is as a single degree of freedom system with a non-linear term to allow for the drag of the device through the water, known as the Morison term. The focus of this system identification is on estimating the dynamic state of the system and estimating the non-linear parameter from observations...

Waves offer an attractive source of renewable energy, with relatively low environmental impact, for communities reasonably close to the sea. Two types of simple wave energy converters (WEC), the heaving buoy WEC and the oscillating flap WEC, are studied. Both WECs are considered as simple energy converters because they can be modelled, to a first a...

We compare spectral and wavelet estimators of the response amplitude operator (RAO) of a linear system, with various input signals and added noise scenarios. The comparison is based on a model of a heaving buoy wave energy device (HBWED), which oscillates vertically as a single mode of vibration linear system. HBWEDs and other single degree of free...

ABSTRAK Maklumat tingkah laku pengguna terhadap keinginan memilih sesuatu produk adalah sangat penting dalam menentukan strategi promosi dan pemasaran produk sesebuah syarikat. Dalam kajian ini, Model Fishbein digunakan untuk menganalisis keinginan memilih jenama produk telefon bimbit di kalangan pengguna. Tiga jenama telefon bimbit yang menjadi pi...