Theses & Dissertations

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https://hdl.handle.net/20.500.14170/2002

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Browsing Theses & Dissertations by Department "Universiti Malaysia Perlis"
  • Publication
    An extended thomas-fermi model with clustering in Nuclei
    ( 2016)
    Nooraihan Abdullah
    In this study, a phenomenological theory of nuclei that includes clustering at the nuclear surface in a general form is presented. The theory elaborates the recently extracted large symmetry energy by Natowitz et al., at low densities of nuclear matter and is fully consistent with the static properties of nuclei. Clusters of all sizes and shapes together with medium alterations are included in a phenomenological way. Discussion about the symmetric nuclear matter properties are presented in detail. Arguments are stated, which bring to an equation of state of nuclear matter consistent with clustering in the low-density region. In addition, the justification and discussion about the properties of asymmetric nuclear matter are given. Due to the clustering, an interesting interpretation of the equation of state of asymmetric nuclear matter comes into view. An extended version of Thomas-Fermi theory is adopted as a framework for nuclei where it also consist of the phenomenological pairing and Wigner contributions. This theory relates the nuclear matter equation of state, which includes clustering at low densities, with clustering in nuclei at the nuclear surface. Calculations are carried out for different equations of state of nuclear matter. This study take into account binding energies of 2149 nuclei for N,Z  8. The significance of the quartic term in symmetry energy is illustrated at and below the saturation density of nuclear matter. It is demonstrated that it is greatly connected to the use of ab initio, a realistic equation of state of neutron matter, especially the contribution originating from the three neutron interactions and rather clustering. The causes for these are presented. The neutron skin thickness in nuclei is found to reduce significantly, for the reason of clustering. The developed theory predicts circumstances and methodologies to be examine both theoretically and experimentally.
      6  7
  • Publication
    Extended hamming distance method for measuring the perfomance of academic staff
    ( 2015)
    Rasyida Md Saad
    This research presents an extended Hamming distance method in measuring the performance of the academic staff. Generally, performance appraisal is responsible in determining the employee works, in which involving in making personnel decisions and employee development. As this process can be used to identify the performance of the employee, a proper method has to be applied in selecting the best employee performance. Multi criteria decision making (MCDM) method is one of the solution for this problem. In this research one of the existing MCDM methods which is a Hamming distance method is extended. Inspired by the Canós algorithm, the extension of the existing algorithm is done. The use of subjective weight and fuzzy linguistic variables are introduced in the newly extended method. The use of criteria weight is essential in evaluating the performance of the alternative. In addition, Shannon’s entropy concept is also applied to determine the most important criteria. Meanwhile, the use of fuzzy linguistic variables will help in dealing with subjective assessment. The extended Hamming distance method is presented in a well-built framework which also depicted in this research. A study case in one of the institute in Universiti Malaysia Perlis, which is Institute of Engineering Mathematics in determining the best academic staff for three years, which are 2010, 2011 and 2012 is presented to validate the extended method. By utilizing the extended method, the most important criteria, the ranking of the academic staff and problems regarding the ranking process for three years are identified. The comparison between the final results of the extended method and TOPSIS method is also done. Based on the final results obtained, it can be concluded that the results for the criteria weight and ranking of the academic staff for the years 2010 and 2011 are different than the year 2012. For the years 2010 and 2011, A22 is declared as the best academic staff. Meanwhile, for the year 2012, the best academic staff is belong to A3. C11 is declared as the most important criteria for the years 2010 and 2011. However, for the year 2012, C6 is declared as the most important criteria. The similarity in the final results between the extended method and TOPSIS method is also identified. Through the application of the extended method it is hope to ease the difficulty in decision making process especially in determining the best performance of the academic staff.
      4  18
  • Publication
    Heuristic method for the modified model of capacitated arc routing problems
    ( 2015)
    Muhamad Hafiz Masran
    The management of waste collection in urban areas is a critical issue for some developing countries especially in Malaysia which requires immediate attention. This study attempts to make an analysis and assessment of the development of the Perlis state waste generation distribution and the optimization of waste collection routes. This thesis describes the architecture design of the mathematical modeling for the mixed graph of Capacitated Arc Routing Problem (MCARP) extended from the Capacitated Arc Routing Problem (CARP). Furthermore, it provides a description of several equations that can be used to obtain efficient collection routes such as capacity vehicles constraint. To get the better result, this study used the existing heuristics method for solving MCARP mathematical modeling. The result shows that the total costs produced are considerably acceptable and are also reasonably improved, although the existing heuristics method do not obtain an optimal solution but in term of the computational time is good and better than other methods for small and intermediate networks especially in the mixed graph problem
      6  15
  • Publication
    Magnetohydrodynamic (MHD) stagnation point flow and heat transfer towards a stretching sheet with suction in a Nanofluid
    ( 2014)
    Nurul Najwa Mansor
    The magnetohydrodynamic (MHD) stagnation point flow and heat transfer towards a stretching sheet in a nanofluid with suction is investigated. The basic equations governing the fluid flow and heat transfer are transformed into nonlinear ordinary differential equation using a similarity transformation, before being solved by means of a shooting method. The effects of suction parameter on the skin friction coefficient, the local Nusselt number and the local Sherwood number as well as the velocity and the temperature profiles are obtained and analyzed. The numerical results indicate that the magnitude skin friction coefficient, the local Nusselt number and the local Sherwood number increase with suction effect.
      2  6
  • Publication
    New algorithm for improving prediction performance in modified radial basis function network
    ( 2020)
    Lim Eng Aik
    In neural networks, the accuracies of the networks are primarily relying on two critical factors, which are the centers and networks weight values. The feed-forward network known as Radial basis function network (RBFN) capable of performing nonlinear approximation on an unknown dataset, classification, pattern recognition, control system, and image processing. However, there are some disadvantages of the RBFN network, such as longer computation time for large datasets, less efficient weight updating, and center selection algorithms that cause low accuracy are identified. Limited data points or overload data points can affect the training of RBFN. Hence, proper size for dataset is required to ensure RBFN is trained using suitable dataset size to lessen the computational time without a significant influence on the accuracy. For RBFN weight updating, the gradient descent (GD) algorithm easily trapped in local minima by random weight generated during the initial stage of training. Meanwhile, the center's selection using the K-means algorithm is known for its sensitivity and high dependency to initial center selection from the input dataset. Therefore, this work proposed solutions for these mentioned disadvantages through modification on a few parts of the RBFN algorithm to improve their performance. First, this work proposed a new dataset reduction formula to obtain a suitable number of a dataset for network training. Next, a modified steepest descent algorithm was proposed for RBFN weight updating during training. Then, a new distance-weighted K-means algorithm is proposed for obtaining more accurate initial centers for RBFN. Finally, this work proposed a new model through a combination of quantum evolutionary algorithm (QEA) and RBFN known as QRBFN. This proposed RBFN demonstrated its abilities in global search and local optimization to effectively provide better accuracy in prediction results. All proposed modified RBFN was tested against the standard RBFN in predictions accuracy on four nonlinear models from literature, and four real-world datasets that consist two time-series datasets (Air pollutant dataset and forex pair EURUSD dataset), and other two datasets are Biochemical Oxygen Demand (BOD) dataset, and Phytoplankton growth dataset. The proposed dataset reduction formula was conducted through experiments where data was tested by a 5 percent step size reduction. The results of this proposed RBFN are compared for root mean square error (RMSE) and area under curve (AUC) values with standard RBFN. The proposed dataset reduction case yielded average results over a 50 percent decrease in time usage and a 20 percent reduction in RMSE. Meanwhile, all proposed RBFN yielded better results and robustness with an average improvement percentage of more than 40 percent in RMSE and AUC results.
  • Publication
    Numerical simulation of stress amplification induced by crack interaction in human femur bone
    ( 2014)
    Noor Alia Md Zain
    This research is about numerical simulation using computational method which study on stress amplification induced by crack interaction in human femur bone. Crack in human femur bone usually occur because of large load or stress applied on it. Usually, the fracture takes longer time to heal itself. The crack interaction is still not well understood due to bone complexity. Thus, brittle fracture behaviour of bone may be underestimated and inaccurate. This study aims in investigating the geometrical effect of double co-planar edge cracks on stress intensity factor (K) in femur bone. Other than that, this research also focus in the amplification effect on fracture behaviour of double co-planar edge cracks, where numerical model is developed using computational method. The concept of fracture mechanics and numerical approaches to solve interacting cracks problems using linear elastic fracture mechanics (LEFM) theory is used. So, it is important to study what is the parameter that can minimize the crack propagation to prevent complete failure. This study has shown that the crack interaction limit (CIL) and crack unification limit (CUL) exist in the model developed. In future development of this research, several improvements will be made such as varying the load, applying thickness on the model and also use different theory or method in calculating the stress intensity factor (K).
      15  13
  • Publication
    Spatial max-stable with cyclic generalizes extreme value model for extreme ground level ozone
    ( 2024)
    Siti Aisyah Zakaria
    The high level of ground-level ozone (GLO) concentration has serious adverse effects on health problems and affects the environment. This study integrates the spatial max-stable processes with the cyclic generalized extreme value (GEV) model to analyze and forecast extreme GLO levels. Spatial extreme provides a framework for analyzing and modelling the behaviour of rare events considering the extreme data pattern and the characteristics of several stations. One key component in this approach is selecting an appropriate GEV marginal distribution based on the data structure of each monitoring station. The choice of marginal distribution depends on whether there is an apparent trend in the extreme data series. In cases where the data exhibit strong seasonal variation, a stationary model may not be appropriate. This study acknowledges the seasonal variation in GLO data at various monitoring stations, influenced by the interchange of monsoons. Therefore, a seasonal variation model is considered as the marginal distribution for the spatial extreme model. Additionally, the study extends the non-stationary model from univariate cases to the spatial extreme model. This model incorporates a cyclic pattern in location parameters to complement the GEV distribution as a new marginal distribution within the max-stable process, a standard dependency model for spatial extreme observed at different locations. The clustering process using hierarchical cluster analysis (HCA) found that all the stations can be grouped into two clusters depending on the same characteristic of the weekly maxima data. The extremal coefficient between 1 to 2 indicates that the stations are dependent on each other’s within the cluster. Validation of the developed model is crucial for accurate predictions. Synthetic data approximating real data characteristics are generated to validate the model and facilitate predictions of future extreme cases based on return values for specific return periods. Return levels, indicating the average amount of extreme events within a specified return period, are used to predict GLO concentration levels across different locations, enhancing the understanding of GLO concentration patterns based on location categories. The presentation of return level results in return level mapping further aids in visualizing and interpreting the predictions for all monitoring stations. The main finding of this study indicates that the return level of GLO concentration increased as the return period increased. The results show that most of the return levels exceed the guideline of MAAQG for 8-hour average that is 0.06 ppm. Notably, the station in Kota Bahru (CA22) stands out with the lowest return levels, while the Shah Alam (CA25) station exhibits the highest estimated values. This high GLO concentration in Shah Alam may be attributed to its urban location, marked by high traffic density, industrial operations, and diverse meteorological influences. In conclusion, this study is highly significant as it offers valuable insights that can be applied in the fields of environmental and climatology, specifically regarding GLO in peninsular Malaysia. The methodology detailed in this study can be adapted for the analysis of other extreme datasets.
  • Publication
    Stability analysis on convection boundary layer stagnation-point flows over a permeable stretching/shrinking surface
    ( 2019)
    Fatinnabila Kamal
    In this thesis, several problems of convection boundary layer flow and heat transfer towards a stretching/shrinking surface along with stability analysis for viscous, nanofluid and micropolar fluids are investigated. There are five problems considered, namely (i) stagnation-point flow and heat transfer over a permeable stretching/shrinking sheet with heat source effect; (ii) magnetohydrodynamic stagnation-point flow towards a permeable stretching/shrinking sheet with slip and heat source/sink effects; (iii) effect three-dimensional stagnation-point flow and heat transfer over a permeable stretching/shrinking sheet with heat source effects in viscous fluid; (iv) MHD stagnation-point flow towards a permeable stretching/shrinking sheet in a nanofluid with chemical reaction; and (v) stagnation-point flow and heat transfer in a micropolar fluid towards a nonlinearly permeable stretching/shrinking sheet. The study starts with the formulations of the mathematical models for every problems. Next, in solving these problems, the governing nonlinear partial differential boundary layer equations are transformed into ordinary differential equations using similarity transformations before being solved numerically using the boundary value problem solver, bvp4c built in Matlab software. The numerical results are then presented in tables and graphs for the skin friction coefficient, the local Nusselt number and the local Sherwood number as well as the velocity, temperature and concentration profiles. The effects of governing parameters have been analysed such as the heat source parameter, the chemical reaction parameter, the suction/injection parameter, the micropolar parameter and the stretching/shrinking parameter. It is observed that the suction/injection effect increase the skin friction coefficient, the local Nusselt number, and the local Sherwood number. Heat source effect has decrease the heat transfer rate. Furthermore, the effect of chemical reaction effect has decrease the local Sherwood number while Micropolar parameter has decrease the skin friction coefficient and heat transfer rate. Further, dual solutions are found for a certain range of the stretching/shrinking parameter. A stability analysis has been carried out to determine which solution is stable for dual solutions exist in all problems considered. The first solution is found to be stable and physically reliable, whereas the second solution is unstable as time passes, thus impractical in the real world applications for a long run.
  • Publication
    Variational Monte Carlo study of light nuclei
    ( 2015)
    Khairul Anwar Mohamad Khazali
    An outstanding problem in Variational Monte Carlo (VMC) calculations with realistic interactions like Argonne V18 and Urbana IX three-body interactions is that p-shell nuclei turn out to be grossly under bound as compared to the Green’s Function Monte Carlo (GFMC) calculations. A similar situation exists in Diffusion Monte Carlo calculations with somewhat simplified interactions. In this thesis, we improve upon the VMC calculations by bringing about several variations in the established procedure of performing variational calculations. In the first variation, the effect of the errors as a function of the number of particles in the variational wave function are analyzed and then a correction through expanding the radial part in terms of a complete set are made and treat the expansion coefficients as variational parameters. Second variation consists in modifying the variational wave function structure. The state of the art variational wave function for s- and p-shell nuclei consists of two parts, where the first part is a Jastrow part operated upon by a symmetrized sum of two-body operatorial correlations and in the second part this outcome is then operated by a sum of unity, operatorial threebody and spin-orbit two-body correlations. A considerable improvement is obtained over the binding energies, wave functions and variance for the light nuclei 3H, 4He and 6Li by using these two variations. We obtain noticeable improvement in the quality of the wave function and lowering of the energies compared to earlier results. The new energies are –8.38 MeV, –28.07 MeV and –29.90 MeV for 3H, 4He, and 6Li respectively. All the computations have been taken away on a multiprocessor machine developed indigenously
      4  13