Displaying publications 21 - 40 of 88 in total

Abstract:
Sort:
  1. Alfa Mohammed Salisu, Ani Shabri
    MATEMATIKA, 2020;36(2):141-156.
    MyJurnal
    This paper proposes A Hybrid Wavelet-Auto-Regressive Integrated Moving Average (W-ARIMA) model to explore the ability of the hybrid model over an ARIMA model. It combines two methods, a Discrete Wavelet Transform (DWT) and ARIMA model using the Standardized Precipitation Index (SPI) drought data for forecasting drought modeling development. SPI data from January 1954 to December 2008 used was divided into two - (80%/20% for training/testing respectively). The results were compared with the conventional ARIMA model with Mean Square Error (MSE) and Mean Average Error (MAE) as an error measure. The results of the proposed method achieved the best forecasting performance.
  2. Farhana Johar, Julies Bong Shu Ai, Fuaada Mohd Siam
    MATEMATIKA, 2020;36(3):235-250.
    MyJurnal
    A new topic of Zero Energy Building (ZEB) is getting famous in research area
    because of its goal of reaching zero carbon emission and low building cost. Renewable
    energy system is one of the ideas to achieve the objective of ZEB. Genetic Algorithm (GA)
    is widely used in many research areas due to its capability to escape from a local minimal
    to obtain a better solution. In our study, GA is chosen in sizing optimization of the
    number of photovoltaic, wind turbine and battery of a hybrid photovoltaic-wind-battery
    system. The aim is to minimize the total annual cost (TAC) of the hybrid energy system
    towards the low cost concept of ZEB. Two GA parameters, which are generation number
    and population size, have been analysed and optimized in order to meet the minimum
    TAC. The results show that the GA is efficient in minimizing cost function of a hybrid
    photovoltaic-wind-battery system with its robustness property.
  3. Mohd Rivaie, Fuziyah Ishak, Nur Idalisa, Nurul Hafawati Fadhilah
    MATEMATIKA, 2020;36(3):197-207.
    MyJurnal
    Conjugate Gradient (CG) methods have an important role in solving large
    scale unconstrained optimization problems. Nowadays, the Three-Term CG method has
    become a research trend of the CG methods. However, the existing Three-Term CG
    methods could only be used with the inexact line search. When the exact line search
    is applied, this Three-Term CG method will be reduced to the standard CG method.
    Hence in this paper, a new Three-Term CG method that could be used with the exact
    line search is proposed. This new Three-Term CG method satisfies the descent condition
    using the exact line search. Performance profile based on numerical results show that
    this proposed method outperforms the well-known classical CG method and some related
    hybrid methods. In addition, the proposed method is also robust in term of number of
    iterations and CPU time.
  4. Rose Irnawaty Ibrahim, Norazmir Mohd Nordin
    MATEMATIKA, 2020;36(3):209-216.
    MyJurnal
    Aging is a good indicator in demographic and health areas as the lifespan
    of the elderly population increases. Based on the government’s Economic Outlook 2019,
    it was found that an aging population would increase the government pension payments
    as the pensioners and their beneficiaries have longer life expectancy. Due to mortality
    rates decreasing over time, the life expectancy tends to increase in the future. The
    aims of this study are to forecast the mortality rates in the years 2020 and 2025 using
    the Heligman-Pollard model and then analyse the effect of mortality improvement on
    the pension cost (annuity factor) for the Malaysian population. However, this study
    only focuses on estimating the annuity factor using life annuities through the forecasted
    mortality rates. The findings indicated that the pension cost is expected to increase if
    the life expectancy of the Malaysian population increases due to the aging population
    the near future. Thus, to reduce pension costs and help the pensioners from insufficient
    financial income, the government needs to consider an extension of the retirement age in
    future.
  5. Olayiwola Babarinsa, Hailiza Kamarulhaili
    MATEMATIKA, 2019;35(1):25-38.
    MyJurnal
    The proposed modified methods of Cramer's rule consider the column vector as well as the coefficient matrix concurrently in the linear system. The modified methods can be applied since Cramer's rule is typically known for solving the linear systems in $WZ$ factorization to yield Z-matrix. Then, we presented our results to show that there is no tangible difference in performance time between Cramer's rule and the modified methods in the factorization from improved versions of MATLAB. Additionally, the Frobenius norm of the modified methods in the factorization is better than using Cramer's rule irrespective of the version of MATLAB used.
  6. Nur Arina Bazilah Aziz
    MATEMATIKA, 2019;35(1):39-49.
    MyJurnal
    Inventory Routing Problem (IRP) has been continuously developed and improved due to pressure from global warming issue particularly related to greenhouse gases (GHGs) emission. The burning of fossil fuel for transportations such as cars, trucks, ships, trains, and planes primarily emits GHGs. Carbon dioxide (CO2) from burning of fossil fuel to power transportation and industrial process is the largest contributor to global GHGs emission. Therefore, the focus of this study is on solving a multi-period inventory routing problem (MIRP) involving carbon emission consideration based on carbon cap and offset policy. Hybrid genetic algorithm (HGA) based on allocation first and routing second is used to compute a solution for the MIRP in this study. The objective of this study is to solve the proposed MIRP model with HGA then validate the effectiveness of the proposed HGA on data of different sizes. Upon validation, the proposed MIRP model and HGA is applied on real-world data. The HGA is found to be able to solve small size and large size instances effectively by providing near optimal solution in relatively short CPU execution time.
  7. Nur Idayu Alimon, Nor Haniza Sarmin, Ahmad Erfanian
    MATEMATIKA, 2019;35(1):51-57.
    MyJurnal
    Topological indices are numerical values that can be analysed to predict the chemical properties of the molecular structure and the topological indices are computed for a graph related to groups. Meanwhile, the conjugacy class graph of is defined as a graph with a vertex set represented by the non-central conjugacy classes of . Two distinct vertices are connected if they have a common prime divisor. The main objective of this article is to find various topological indices including the Wiener index, the first Zagreb index and the second Zagreb index for the conjugacy class graph of dihedral groups of order where the dihedral group is the group of symmetries of regular polygon, which includes rotations and reflections. Many topological indices have been determined for simple and connected graphs in general but not graphs related to groups. In this article, the Wiener index and Zagreb index of conjugacy class graph of dihedral groups are generalized.
  8. Siti Nur Haseela Izani, Anati Ali
    MATEMATIKA, 2019;35(2):187-200.
    MyJurnal
    The heat and mass transfer of steady magnetohydrodynamics of dusty Jeffrey fluid past an exponentially stretching sheet in the presence of thermal radiation have been investigated. The main purpose of this study is to conduct a detailed analysis of flow behaviour of suspended dust particles in non-Newtonian fluid. The governing equations hav been converted into dimensionless form, and then solved numerically via the Keller-box method. The expression of Sherwood number, Nusselt number and skin friction have been evaluated, and then displayed in tabular forms. Velocity, temperature and concentration profiles are presented graphically. It is observed that large value of dust particles mass concentration parameter has reduced the flow velocity significantly. Increase in radiation parameter enhances the temperature, whereas the increment in Schmidt number parameter reduces the concentration.
  9. Nur Azira Jasman, Nur Adlin Lina Normisyidi, Yeak Sue Hoe, Ahmad Razin Zainal Abidin, Mohd Ridza Mohd Haniffah
    MATEMATIKA, 2019;35(301):15-32.
    MyJurnal
    Subsea cable laying is a risky and challenging operation faced by engineers, due to many uncertainties arise during the operation. In order to ensure that subsea cables are laid out diligently, the analysis of subsea cable tension during the laying operation is crucial. This study focuses on the fatigue failure of cables that will cause large hang-off loads based on catenary configuration after laying operation. The presented problem was addressed using mathematical modelling with consideration for a number of defining parameters, which include external forces such as current velocity and design parameters such as cable diameter. There were two types of subsea cable tension analyses studied: tensional analysis of catenary configurations and tensional analysis of lazy wave configurations. The latter involved a buoyancy module that was incorporated in the current catenary configuration that reduced subsea cable tension and enhanced subsea cable lifespan. Both analyses were solved using minimization through the gradient- based approach concerning on the tensional analysis of the subsea cable in different configurations. Lazy wave configurations were shown to successfully reduce cable tension, especially at the hang-off section.
  10. N. A. Majid, N. F. Mohammad, A. R. M. Kasim, S. Shafie
    MATEMATIKA, 2019;35(3):397-413.
    MyJurnal
    In this paper, the problem of forced convection flow of micropolar fluid of
    lighter density impinging orthogonally on another heavier density of micropolar fluid
    on a stretching surface is investigated. The boundary layer governing equations are
    transformed from partial differential equations into a system of nonlinear ordinary
    differential equations using similarity transformation and solved numerically using dsolve
    function in maple software version 2016. The velocity, microrotation and temperature of
    micropolar fluid are analyzed. It is found that both upper fluid and lower fluid display
    opposite behaviour when micropolar parameter k various with strong concentration
    n = 0, pr = 7 and stretching parameter = 0.5. The results also show that stretching
    surface exert the force that increasing the velocity of micropolar fluid.
  11. Noorehan Yaacob, Nur Azura Noor Azhuan, Sharidan Shafie, Mohd Ariff Admon
    MATEMATIKA, 2019;35(301):139-148.
    MyJurnal
    Invadopodia are finger-like protrusions located at subcellular membrane which can lead to cancer cell invasion. The formation of invadopodia involves several steps such as actin polymerizations, degradation of extracellular matrix which produce ligand and signal stimulation that is occurred from the binding of ligand with epidermal growth factor receptor. In this paper, a mathematical model of signal transduction is investigated. Both signal and ligand are represented by Laplace equation with Dirichlet boundary condition for each region. The cell membrane is treated as free boundary surface to separate any activity that occurred in intracellular and extracellular regions. The motion of the interface is taken as gradient of interior signal and the cell membrane is set as zero level set function. The problem is solved numerically using finite difference scheme of upwind, interpolation and extrapolation methods. The results showed that the formation of invadopodia is formed when protrusions exist on the cell membrane.
  12. Khang Yi Sim, Siok Kun Sek
    MATEMATIKA, 2019;35(301):79-97.
    MyJurnal
    The effect of oil shock on the global economy is evident through many studies. However, the effect is heterogeneous over time. One of the reasons that lead to such different impacts is due to the oil source that is either the oil shock is demand or supply- driven. Applying the structural vector autoregressive (SVAR) model to generate the three oil shocks based on the three oil sources (oil supply, oil demand and oil specific- demand), we extended the examination on the effect of oil shock on the global economy using the threshold regression. Our results reveal the threshold effects of oil directly and indirectly on the global economy. The impacts of oil shocks differ across sectors, implying oil intensity, as well as oil sources, are the factors that determine the impact of oil shocks on the global economy. Overall, the oil specific-demand shock is more influential among the three oil shocks. Hence, the global economy is oil demand-driven. Besides that, the impact of oil is relatively large in the energy sector when compared to the non-energy sector and precious metals industry. Despite that, the impact of oil shocks is small if compared to the non-oil shocks such as exchange rate changes and global consumer price inflation shock. Consequently, non-oil shocks are the main determinants of the global economic fluctuation. The study leads to a better understanding of the transmission of oil shock and its sources, the interaction between oil and economic indicators and the policy implication due to oil dependency/ intensity.
  13. Eng Woo Chiew, Siok Kun Sek
    MATEMATIKA, 2019;35(301):99-122.
    MyJurnal
    Price stability is one of the main policy objectives that is targeted by policymakers in many countries. Price uncertainty occurs due to the changes in market structure and consumer preference and expectation, which may affect price stability. In this study, the researchers aimed to examine the effects of price uncertainty of consumer price disaggregation in Malaysian sectors. To be specific, the researchers were seeking to discover on how domestic and global commodity prices can affect sectoral Consumer Price Index (CPI) on price inflation in Malaysia and most importantly, whether the effect is different for economic sectors in Malaysia. In addition, the effects of other factors (i.e., internal and external factors) on Malaysian sectoral CPI inflation were also studied. The threshold generalized autoregressive conditional heteroscedasticity (TGARCH) model was used to generate the price uncertainties. For the purpose of analysis, the threshold regression approach was applied based on time series of each single sector, followed by a combination of panel data of all sectors. The results differed across sectors, revealing that the impact of price uncertainties was determined by the sensitivity of each sector towards the price uncertainties. The effect of price increase is larger than the effect of price decrease. Price fluctuations were obvious in sectors that were dependent on consumer price or commodity price. Exchange rate and oil price inflation had also greatly influenced the CPI inflation.
  14. Nur Azlina Mat Noor, Sharidan Shafie, Mohd Ariff Admon
    MATEMATIKA, 2019;35(301):33-52.
    MyJurnal
    The hydromagnetic mixed convection flow of Cassonnano fluid under the influence of chemical reaction,thermal radiation and heat generation or absorption is investigated. The flow is induced due to unsteady nonlinearly stretching sheet saturated in a porous medium. The governing nonlinear coupled partial differential equations are converted into the system of coupled ordinary differential equations using similarity transformations and then solved numerically via Keller box method. The effects of pertinent parameters on velocity, temperature and nanoparticles concentration as well as wall shear stress, heat and mass transfer rate are analyzed and displayed graphically. The results for skin friction coefficient and local Nusselt number are compared with previously published work and found to be in good agreement. Findings demonstrate that increase in Casson parameter enhanced the friction factor and heat transfer rate. It is noticed that the heat transfer rate is declined with increment in Brownian motion and thermophoresis parameters. The nanoparticles concentration is seen to be higher in generative chemical reaction and opposite effect is observed in destructive chemical reaction. Increase in unsteadiness parameter decreased the fluid velocity, temperature and nanoparticles concentration. The magnitude of wall shear stress is also reduced with increase in unsteadiness and porous medium parameters.
  15. Siti Nabilah Syuhada Abdullah, Ani Shabri, Ruhaidah Samsudin
    MATEMATIKA, 2019;35(301):53-64.
    MyJurnal
    Since rice is a staple food in Malaysia, its price fluctuations pose risks to the producers, suppliers and consumers. Hence, an accurate prediction of paddy price is essential to aid the planning and decision-making in related organizations. The artificial neural network (ANN) has been widely used as a promising method for time series forecasting. In this paper, the effectiveness of integrating empirical mode decomposition (EMD) into an ANN model to forecast paddy price is investigated. The hybrid method is applied on a series of monthly paddy prices from February 1999 up to May 2018 as recorded in the Malaysian Ringgit (MYR) per metric tons. The performance of the simple ANN model and the EMD-ANN model was measured and compared based on their root mean squared Error (RMSE), mean absolute error (MAE) and mean percentage error (MPE). This study finds that the integration of EMD into the neural network model improves the forecasting capabilities. The use of EMD in the ANN model made the forecast errors reduced significantly, and the RMSE was reduced by 0.012, MAE by 0.0002 and MPE by 0.0448.
  16. Nurfarah Zulkifli
    MATEMATIKA, 2019;35(3):357-369.
    MyJurnal
    Let g be a finite group. The probability of a random pair of elements in g are
    said to be co-prime when the greatest common divisor of order x and y where x and y in
    g, is equal to one. Meanwhile the co-prime graph of a group is defined as a graph whose
    vertices are elements of g and two distinct vertices are adjacent if and only if the greatest
    common divisor of order x and y is equal to one. In this paper, the co-prime probability
    and its graphs such as the types and the properties of the graph are determined.
  17. Afeez Abidemi, Rohanin Ahmad, Nur Arina Bazilah Aziz
    MATEMATIKA, 2019;35(301):149-170.
    MyJurnal
    This study presents a two-strain deterministic model which incorporates Dengvaxia vaccine and insecticide (adulticide) control strategies to forecast the dynamics of transmission and control of dengue in Madeira Island if there is a new outbreak with a different virus serotypes after the first outbreak in 2012. We construct suitable Lyapunov functions to investigate the global stability of the disease-free and boundary equilibrium points. Qualitative analysis of the model which incorporates time-varying controls with the specific goal of minimizing dengue disease transmission and the costs related to the control implementation by employing the optimal control theory is carried out. Three strategies, namely the use of Dengvaxia vaccine only, application of adulticide only, and the combination of Dengvaxia vaccine and adulticide are considered for the controls implementation. The necessary conditions are derived for the optimal control of dengue. We examine the impacts of the control strategies on the dynamics of infected humans and mosquito population by simulating the optimality system. The disease-free equilibrium is found to be globally asymptotically stable whenever the basic reproduction numbers associated with virus serotypes 1 and j (j ∈ {2,3,4}), respectively, satisfy R01,R0j ≤ 1, and the boundary equilibrium is globally asymptotically stable when the related R0i (i = 1,j) is above one. It is shown that the strategy based on the combination of Dengvaxia vaccine and adulticide helps in an effective control of dengue spread in the Island.
  18. Amira Fadina Ahmad Fadzil, Rabiha Mahmoud, Nor Haniza Sarmin, Ahmad Erfanian
    MATEMATIKA, 2019;35(1):59-65.
    MyJurnal
    Let G be a dihedral group and ??cl G its conjugacy class graph. The Laplacian energy of the graph, LE(??cl G) is defined as the sum of the absolute values of the difference between the Laplacian eigenvalues and the ratio of twice the edges number divided by the vertices number. In this research, the Laplacian matrices of the conjugacy class graph of some dihedral groups, generalized quaternion groups, quasidihedral groups and their eigenvalues are first computed. Then, the Laplacian energy of the graphs are determined.
  19. Mohd Ismail Abd Aziz, Noryanti Nasir, Akbar Banitalebi
    MATEMATIKA, 2019;35(1):95-104.
    MyJurnal
    Successful oil palm plantation should have high profit, clean and environmental friendly. Since oil palm trees have a long life and it takes years to be fully grown, controlling the felling rate of the oil palm trees is a fundamental challenge. It needs to be addressed in order to maximize oil production. However, a good arrangement of the felling of the oil palm trees may also affect the amount of carbon absorption. The objec- tive of this study is to develop an optimal felling model of the oil palm plantation system taking into account both oil production and carbon absorption. The model facilitates in providing the optimal control of felling rate that results in maximizing both oil produc- tion and carbon absorption. With this aim, the model is formulated considering oil palm biomass, carbon absorption rate, oil production rate and the average prices of carbon and oil palm. A set of real data is used to estimate the parameters of the model and numerical simulation is conducted to highlight the application of the proposed model. The resulting parameter estimation that leads to an optimal control of felling rate problem is solved.
  20. Amira Fadina Ahmad Fadzil, Nor Haniza Sarmin, Ahmad Erfanian
    MATEMATIKA, 2019;35(3):371-376.
    MyJurnal
    Let g be a finite group and s be a subset of g, where s does not include
    the identity of g and is inverse closed. A cayley graph of a group g with respect to the
    subset s is a graph, where its vertices are the elements of g and two vertices a and b
    are connected if ab-1 is in the subset s. The energy of a cayley graph is the sum of all
    absolute values of the eigenvalues of its adjacency matrix. In this paper, we consider a
    specific subset s = {b, ab, . . . , An-1b} for dihedral groups of order 2n, where n 3 and find
    the cayley graph with respect to the set. We also calculate the eigenvalues and compute
    the energy of the respected cayley graphs. Finally, the generalization of the energy of the
    respected cayley graphs is found.
Related Terms
Filters
Contact Us

Please provide feedback to Administrator (afdal@afpm.org.my)

External Links