Zaitul Marlizawati Zainuddin - Academia.edu (original) (raw)
Papers by Zaitul Marlizawati Zainuddin
Mathematika, 2008
Location analysis is concerned with locating one or more service facilities while fulfilling some... more Location analysis is concerned with locating one or more service facilities while fulfilling some constraints such as the demand of the customers and minimizing the total cost. Despite the cost of transporting goods or services, there is a fixed cost associated with opening a given facility such as the cost of the land, taxes or trunking (or hauling) cost to supply product, services and labour. This cost may vary from one area to another. The aim of this study is to put forward a Simulated Annealing (SA) procedure for solving the uncapacitated continuous location-allocation problem in the presence of a zone-dependent fixed cost. Simulated Annealing is one of the meta-heuristic methods derived from the annealing process of a solid. Several parameters in SA will be tested such as initial starting points, initial temperature and cooling schedules. Data set for 50 customer problem taken from the literature is used. The problems of locating 2 to 15 facilities are solved by using C++. The...
A linear multiple regression based regionalization method has been proposed in this study to simu... more A linear multiple regression based regionalization method has been proposed in this study to simulate streamflow in ungauged catchment in the east coast of peninsular Malaysia. Identification of unit Hydrographs And Component flows from Rainfall, Evapotranspiration and Streamflow (IHACRES) rainfall-runoff model was used to develop the relationship between model parameters and physical catchment descriptors of eight gauged catchments distributed over the west coast of peninsular Malaysia. The IHACRES model was calibrated and validated individually for each catchment with the available data for the time periods varying between three to sixteen years. The Nash-Sutcliffe efficiency index was used as criteria to evaluate the model performance. As the relationships between the physical catchment descriptors and hydrologic response characteristics are not necessarily linear, different forms of transformations were performed in order to find the most appropriate relationship. Finally, the o...
Scientific Research and Essays, 2011
Unit selection method has become the main approach in speech synthesis. The increasing size of re... more Unit selection method has become the main approach in speech synthesis. The increasing size of recorded speech has resulted in better synthesis speech quality but at the same time also resulted in more expensive computational effort. Therefore, this paper proposes a combination of segmental context matching procedure and Simulated Annealing (SA) in unit selection to improve the quality of synthetic speech and reduce the computational time. The process of unit selection is based on minimization of two costs: target cost and join cost. The segmental context (target cost), the first stage of unit selection matching procedure used to narrow down the search space, followed by an optimization method which is SA to find the units sequence with minimum join cost. Result shows that the synthesis words produced by the proposed system are 15.48% better compared to previous version of corpus-based Malay Text-to-Speech system. Future works may focus on combining SA with other heuristic methods t...
The European Physical Journal Plus, 2021
Coronavirus disease 2019 (COVID-19) pandemic has posed a serious threat to both the human health ... more Coronavirus disease 2019 (COVID-19) pandemic has posed a serious threat to both the human health and economy of the affected nations. Despite several control efforts invested in breaking the transmission chain of the disease, there is a rise in the number of reported infected and death cases around the world. Hence, there is the need for a mathematical model that can reliably describe the real nature of the transmission behaviour and control of the disease. This study presents an appropriately developed deterministic compartmental model to investigate the effect of different pharmaceutical (treatment therapies) and nonpharmaceutical (particularly, human personal protection and contact tracing and testing on the exposed individuals) control measures on COVID-19 population dynamics in Malaysia. The data from daily reported cases of COVID-19 between 3 March and 31 December 2020 are used to parameterize the model. The basic reproduction number of the model is estimated. Numerical simulations are carried out to demonstrate the effect of various control combination strategies involving the use of personal protection, contact tracing and testing, and treatment control measures on the disease spread. Numerical simulations reveal that the implementation of each strategy analysed can significantly reduce COVID-19 incidence and prevalence in the population. However, the results of effectiveness analysis suggest that a strategy that combines both the pharmaceutical and non-pharmaceutical control measures averts the highest number of infections in the population.
Malaysian Journal of Fundamental and Applied Sciences, 2017
Nowadays, in unstable economic environment, oil refining company is facing fluctuating crude oil ... more Nowadays, in unstable economic environment, oil refining company is facing fluctuating crude oil price that causes unstable profit margin. Fluctuating crude oil price leads to difficulty in forecasting raw material procurement. Inaccurate forecast leads to inefficient decision making in optimizing refining company profit margin. In order to overcome an inaccurate in forecasting raw material procurement, an appropriate study of forecasting model is needed. Thus the objective of this study is to model fluctuating crude oil price based on geometric Brownian motion and mean reverting Ornstein-Uhlenbeck process and also to forecast fluctuating crude oil price with structural break. In modeling crude oil price, the information on whether the structural break exists is very crucial due to the long memory property might be camouflaged by the existence of the structural break. In this study, we employed long memory test to West Texas Intermediate (WTI) daily data from 2nd January 1986 to 31s...
Journal of Physics: Conference Series, 2019
Simulated annealing (SA) is considered a valuable stochastic technique for resolving difficulties... more Simulated annealing (SA) is considered a valuable stochastic technique for resolving difficulties associated with comprehensive multidimensional optimisation, which guarantees optimal global convergence. This study explores the use of SA to address the challenges of redesigning warehouse networks and relates the effectiveness of three (3) diverse SA cooling schedules, namely; the basic geometric, logarithmic, and linear. The broad computational findings performed and described in the study indicate that the geometric cooling schedule generates consistent, superior quality, and timely solutions compared to the other schemes.
Jurnal Teknologi, 2016
Minimization of cost is very important in airline as great profit is an important objective for a... more Minimization of cost is very important in airline as great profit is an important objective for any airline system. One way to minimize the costs in airline is by developing an integrated planning process. Airline planning consists of many difficult operational decision problems including aircraft routing and crew pairing problems. These two sub-problems, though interrelated in practice, are usually solved sequentially leading to suboptimal solutions. We propose an integrated aircraft routing and crew pairing problem model, one approach to generate the feasible aircraft routes and crew pairs, followed by three approaches to solve the integrated model. The integrated aircraft routing and crew scheduling problem is to determine a minimum cost aircraft routes and crew schedules while each flight leg is covered by one aircraft and one crew. The first approach is an integer programming solution method, the second formulation is developed in a way to lend itself to be used efficiently by ...
Malaysian Journal of Fundamental and Applied Sciences, 2014
The facility layout design has been regarded as the key to improve plant productivity, which are ... more The facility layout design has been regarded as the key to improve plant productivity, which are relevant to both manufacturing and service sectors. Facility Layout Problems (FLPs) are known to be NP-hard problems; various optimization approaches for small problems and heuristic approaches for the larger problems have been proposed to elucidate the problem. A mathematical model is developed for the unequal size facility layout problem with fixed flow between departments. We are considering the orientations of the departments with various sizes and aims to minimize the distance traveled by people, material, and other supporting services in the safest and most effective manner. Some of the constraints considered in the modeling are the restricted areas, reserved departmentry locations, and also the irregularity of the shapes of manufacturing layout. This paper focuses on the mathematical model and the solution of the non-quadratic assignment problem (non-QAP) by hybridizing the meta-h...
MATEMATIKA, 2018
Recently, oil refining industry is facing with lower profit margin due to uncertainty. This cause... more Recently, oil refining industry is facing with lower profit margin due to uncertainty. This causes oil refinery to include stochastic optimization in making a decision to maximize the profit. In the past, deterministic linear programming approach is widely used in oil refinery optimization problems. However, due to volatility and unpredictability of oil prices in the past ten years, deterministic model might not be able to predict the reality of the situation as it does not take into account the uncertainties thus, leads to non-optimal solution. Therefore, this study will develop two-stage stochastic linear programming for the midterm production planning of oil refinery to handle oil price volatility. Geometric Brownian motion (GBM) is used to describe uncertainties in crude oil price, petroleum product prices, and demand for petroleum products. This model generates the future realization of the price and demands with scenario tree based on the statistical specification of GBM using...
Journal of Physics: Conference Series, 2017
View the article online for updates and enhancements. Related content Meta-heuristic algorithm to... more View the article online for updates and enhancements. Related content Meta-heuristic algorithm to solve two-sided assembly line balancing problems A D Wirawan and A Maruf-Research on three-phase unbalanced distribution network reconfiguration strategy Shuang Hu, Ke-Jun Li, Yanshun Xu et al.-Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Journal of Physics: Conference Series, 2017
Now a day, several companies consider downsizing their distribution networks in ways that involve... more Now a day, several companies consider downsizing their distribution networks in ways that involve consolidation or phase-out of some of their current warehousing facilities due to the increasing competition, mounting cost pressure and taking advantage on the economies of scale. Consequently, the changes on economic situation after a certain period of time require an adjustment on the network model in order to get the optimal cost under the current economic conditions. This paper aimed to develop a mixed-integer linear programming model for a two-echelon warehouse network redesign problem with capacitated plant and uncapacitated warehouses. The main contribution of this study is considering capacity constraint for existing warehouses. A Simulated Annealing algorithm is proposed to tackle with the proposed model. The numerical solution showed the model and method of solution proposed was practical.
Indian Journal of Science and Technology, 2017
Traditionally, aircraft routing and crew pairing problems are solved sequentially with the aircra... more Traditionally, aircraft routing and crew pairing problems are solved sequentially with the aircraft routing problem solved first followed by the crew pairing problem. But in some cases, the results are suboptimal. In order to overcome this problem, both problems will be composed in one model. Although the integration model is challenging to solve but it is practically useful in airlines operations for getting the optimal solutions. In this study, we proposed the constructive heuristic method and the genetic algorithm (GA) in producing the feasible paths. After that, we will solve those two types of feasible paths in the integrated model by using three approaches which are the integer linear programming (ILP), Dantzig Wolfe decomposition method and Benders decomposition method. Computational results show that the obtained feasible path from the constructive heuristic method and solved by the Dantzig Wolfe decomposition method is more effective while the paths from the GA and solved by the Dantzig Wolfe decomposition method is good in finding the minimum computational time. From the results obtained, all the flight legs and crew pairing are used only once. There are four type of aircrafts are used in testing the performance of the approaches which based on local flights in Malaysia for seven days. The solutions of the feasible paths from GA is more advantageous in term of the computational times compare to the solutions by using the feasible paths from constructive heuristic method.
Indian Journal of Science and Technology, 2015
Background/Objectives: This paper focused on integrated Continuous Berth Allocation Problem (BAPC... more Background/Objectives: This paper focused on integrated Continuous Berth Allocation Problem (BAPC) and Quay Crane Scheduling Problem (QCSP) by considering non-crossing constraint to make it more realistic. Methods/Statistical analysis: Genetic Algorithm (GA) is a metaheuristic method that has been used extensively in Berth Allocation Problem (BAP). Crossover and mutation are selected as operators in this paper. Findings: The integrated model is formulated as a Mix Integer Problem (MIP) with the objective to minimize the sum of the processing times. A vessel's processing time is measured between arrival and departure includingwaiting time to be berthed and servicing time.The new algorithm of GA arecompatible with the integrated model and useful for finding near-optimal solutions. Three phase new algorithms of GA are proposed and provide a wider search to the solution space. Application/Improvements: Three phase of GA is another significant and promising variant of genetic algorithms in BAPC and QCSP. The probabilities of crossover and mutation determine the degree of solution accuracy and the convergence speed that GA canobtain. By using fixed values of crossover and mutation, the algorithm utilize the population information in each generation and adaptively adjust the crossover and mutation. So, the population diversity and sustain the convergence capacity is maintained.
2016 International Conference on Industrial Engineering, Management Science and Application (ICIMSA), 2016
This paper presents the simultaneous integration model of berth allocation and quay crane schedul... more This paper presents the simultaneous integration model of berth allocation and quay crane scheduling. Berths and quay cranes are both critical resources in port container terminals. The mathematical model uses a mixed integer linear programming with multiple objectives generated by considering various practical constraints. Small data instances have been taken to validate the integrated model. A numerical experiment was conducted by using LINGO programming software to evaluate the performance and to obtain the exact solution of the suggested model.
Recently, crude oil price becomes volatile and have been the popular issue to be discussed in eve... more Recently, crude oil price becomes volatile and have been the popular issue to be discussed in every country. Oil price fluctuations have major impact on the overall economy and finally will lead to increase in the inflation rate. It is important to describe these oil price fluctuations mathematically. This study aims to describe the above phenomena using geometric Brownian motion. Two crude oil prices, namely WTI and Brent have been analyzed based on daily oil price data from year 2000 until year 2015. Through the analysis using model assessment and model determination, crude oil price after year 2000 follows geometric Brownian motion process. We conclude that oil price fluctuations follow a geometric Brownian motion process without considering unexpected incidents.
Modern Applied Science, 2016
In airline operations planning, there are four problems which are schedule design, fleet assignme... more In airline operations planning, there are four problems which are schedule design, fleet assignment, aircraft routing and crew pairing problem. Those problems are sequentially and interdependent. Aircraft routing and crew pairing problem are hard to solve and normally crew pairing problem dependent to the aircraft routing problem which gives the suboptimal solutions. As minimizing the costs is important in the airline system, so in order to tackle suboptimal solutions, aircraft routing problem and crew pairing problem are being integrated in one model. For solving the integrated model, the feasible aircraft routes and crew pairs are required. Because of that, a method is being proposed in this work for generating the feasible aircraft routes and crew pairs which is the constructive heuristic method. By using the generic aircraft routes and crew pairs, the integrated model then being solve by two approaches. The first approach is the exact method called the integer linear programming...
Video communication over Vehicular Ad Hoc Networks (VANETs) has many applications, such as emerge... more Video communication over Vehicular Ad Hoc Networks (VANETs) has many applications, such as emergency video transmission, commercial advertisements and inter-vehicle digital entertainment. However, in urban vehicular scenario, delivering video streams to highly mobile vehicles is indeed a challenging task due to high radio interference, channel loss rate and burst packet losses. Thus, designing an error resilient scheme for reliable video geocasting in such harsh scenarios needs to be addressed. In this paper, we propose an error resilient scheme based on packet level Forward Error Correction (FEC) and interleaving technique for reliable video geocasting over VANET. The proposed scheme is able to adapt channel variations by using a Real Time Control Protocol (RTCP) report of vehicles within communication range of the video source. To achieve a fair comparison with other error protection schemes, we have implemented a proposed error resilient scheme in Network Simulator 2 (NS 2). The results of simulation based study show that the proposed scheme is able to improve perceived video quality and protection efficiency while minimizing bandwidth overhead (introduced by proactive error recovery) in urban vehicular scenarios
Network Protocols and Algorithms, 2013
A Vehicular Ad hoc Network (VANET) is a type of wireless ad hoc network that facilitates ubiquito... more A Vehicular Ad hoc Network (VANET) is a type of wireless ad hoc network that facilitates ubiquitous connectivity between vehicles in the absence of fixed infrastructure. Multi-hop routing and beaconing approaches are two important research challenges in high mobility vehicular networks. Routing protocols are divided into two categories of topology-based and position-based routing protocols. In this article, we perform a comparative study among the existing routing solutions, which explores the main advantages and drawbacks behind their design. After implementing the representatives of geographical and topology routing protocols, we analyze the simulation results and discuss the strengths and weaknesses of these routing protocols in regard to their suitability to vehicular networks. Lastly, we discuss the open issues and research directions related to VANET routing protocols.
In this research, an integrated approach is presented to simultaneously solve quay crane scheduli... more In this research, an integrated approach is presented to simultaneously solve quay crane scheduling and yard truck scheduling problems. A mathematical model was proposed considering the main real-world assumptions such as quay crane non-crossing, precedence constraints and variable berthing times for vessels with the aim of minimizing vessels completion time. Based on the numerical results, this proposed mathematical model has suitable efficiency for solving small instances. Two versions of imperialist competitive algorithm (ICA) are presented to heuristically solve the problem. The grouping version of algorithm (G-ICA) is used to solve the large-sized instances based on considering the allocation of trucks as a grouping problem. Effectiveness of the proposed metaheuristics on small-sized problems is compared with the optimal results of the mathematical model. In order to compare the efficiency of the proposed algorithms for large-sized instances, several instances were generated and solved, and the performance of algorithms has been compared with each other. Moreover, a simulated annealing (SA) algorithm is developed to solve the problem and evaluate the performance of the proposed ICA algorithms. Based on the experimental results, the G-ICA has a better performance compared to the ICA and SA. Also an instance of a container terminal in Iran has been investigated which shows that the proposed model and solution methods are applicable in real-world problems.
Mathematika, 2008
Location analysis is concerned with locating one or more service facilities while fulfilling some... more Location analysis is concerned with locating one or more service facilities while fulfilling some constraints such as the demand of the customers and minimizing the total cost. Despite the cost of transporting goods or services, there is a fixed cost associated with opening a given facility such as the cost of the land, taxes or trunking (or hauling) cost to supply product, services and labour. This cost may vary from one area to another. The aim of this study is to put forward a Simulated Annealing (SA) procedure for solving the uncapacitated continuous location-allocation problem in the presence of a zone-dependent fixed cost. Simulated Annealing is one of the meta-heuristic methods derived from the annealing process of a solid. Several parameters in SA will be tested such as initial starting points, initial temperature and cooling schedules. Data set for 50 customer problem taken from the literature is used. The problems of locating 2 to 15 facilities are solved by using C++. The...
A linear multiple regression based regionalization method has been proposed in this study to simu... more A linear multiple regression based regionalization method has been proposed in this study to simulate streamflow in ungauged catchment in the east coast of peninsular Malaysia. Identification of unit Hydrographs And Component flows from Rainfall, Evapotranspiration and Streamflow (IHACRES) rainfall-runoff model was used to develop the relationship between model parameters and physical catchment descriptors of eight gauged catchments distributed over the west coast of peninsular Malaysia. The IHACRES model was calibrated and validated individually for each catchment with the available data for the time periods varying between three to sixteen years. The Nash-Sutcliffe efficiency index was used as criteria to evaluate the model performance. As the relationships between the physical catchment descriptors and hydrologic response characteristics are not necessarily linear, different forms of transformations were performed in order to find the most appropriate relationship. Finally, the o...
Scientific Research and Essays, 2011
Unit selection method has become the main approach in speech synthesis. The increasing size of re... more Unit selection method has become the main approach in speech synthesis. The increasing size of recorded speech has resulted in better synthesis speech quality but at the same time also resulted in more expensive computational effort. Therefore, this paper proposes a combination of segmental context matching procedure and Simulated Annealing (SA) in unit selection to improve the quality of synthetic speech and reduce the computational time. The process of unit selection is based on minimization of two costs: target cost and join cost. The segmental context (target cost), the first stage of unit selection matching procedure used to narrow down the search space, followed by an optimization method which is SA to find the units sequence with minimum join cost. Result shows that the synthesis words produced by the proposed system are 15.48% better compared to previous version of corpus-based Malay Text-to-Speech system. Future works may focus on combining SA with other heuristic methods t...
The European Physical Journal Plus, 2021
Coronavirus disease 2019 (COVID-19) pandemic has posed a serious threat to both the human health ... more Coronavirus disease 2019 (COVID-19) pandemic has posed a serious threat to both the human health and economy of the affected nations. Despite several control efforts invested in breaking the transmission chain of the disease, there is a rise in the number of reported infected and death cases around the world. Hence, there is the need for a mathematical model that can reliably describe the real nature of the transmission behaviour and control of the disease. This study presents an appropriately developed deterministic compartmental model to investigate the effect of different pharmaceutical (treatment therapies) and nonpharmaceutical (particularly, human personal protection and contact tracing and testing on the exposed individuals) control measures on COVID-19 population dynamics in Malaysia. The data from daily reported cases of COVID-19 between 3 March and 31 December 2020 are used to parameterize the model. The basic reproduction number of the model is estimated. Numerical simulations are carried out to demonstrate the effect of various control combination strategies involving the use of personal protection, contact tracing and testing, and treatment control measures on the disease spread. Numerical simulations reveal that the implementation of each strategy analysed can significantly reduce COVID-19 incidence and prevalence in the population. However, the results of effectiveness analysis suggest that a strategy that combines both the pharmaceutical and non-pharmaceutical control measures averts the highest number of infections in the population.
Malaysian Journal of Fundamental and Applied Sciences, 2017
Nowadays, in unstable economic environment, oil refining company is facing fluctuating crude oil ... more Nowadays, in unstable economic environment, oil refining company is facing fluctuating crude oil price that causes unstable profit margin. Fluctuating crude oil price leads to difficulty in forecasting raw material procurement. Inaccurate forecast leads to inefficient decision making in optimizing refining company profit margin. In order to overcome an inaccurate in forecasting raw material procurement, an appropriate study of forecasting model is needed. Thus the objective of this study is to model fluctuating crude oil price based on geometric Brownian motion and mean reverting Ornstein-Uhlenbeck process and also to forecast fluctuating crude oil price with structural break. In modeling crude oil price, the information on whether the structural break exists is very crucial due to the long memory property might be camouflaged by the existence of the structural break. In this study, we employed long memory test to West Texas Intermediate (WTI) daily data from 2nd January 1986 to 31s...
Journal of Physics: Conference Series, 2019
Simulated annealing (SA) is considered a valuable stochastic technique for resolving difficulties... more Simulated annealing (SA) is considered a valuable stochastic technique for resolving difficulties associated with comprehensive multidimensional optimisation, which guarantees optimal global convergence. This study explores the use of SA to address the challenges of redesigning warehouse networks and relates the effectiveness of three (3) diverse SA cooling schedules, namely; the basic geometric, logarithmic, and linear. The broad computational findings performed and described in the study indicate that the geometric cooling schedule generates consistent, superior quality, and timely solutions compared to the other schemes.
Jurnal Teknologi, 2016
Minimization of cost is very important in airline as great profit is an important objective for a... more Minimization of cost is very important in airline as great profit is an important objective for any airline system. One way to minimize the costs in airline is by developing an integrated planning process. Airline planning consists of many difficult operational decision problems including aircraft routing and crew pairing problems. These two sub-problems, though interrelated in practice, are usually solved sequentially leading to suboptimal solutions. We propose an integrated aircraft routing and crew pairing problem model, one approach to generate the feasible aircraft routes and crew pairs, followed by three approaches to solve the integrated model. The integrated aircraft routing and crew scheduling problem is to determine a minimum cost aircraft routes and crew schedules while each flight leg is covered by one aircraft and one crew. The first approach is an integer programming solution method, the second formulation is developed in a way to lend itself to be used efficiently by ...
Malaysian Journal of Fundamental and Applied Sciences, 2014
The facility layout design has been regarded as the key to improve plant productivity, which are ... more The facility layout design has been regarded as the key to improve plant productivity, which are relevant to both manufacturing and service sectors. Facility Layout Problems (FLPs) are known to be NP-hard problems; various optimization approaches for small problems and heuristic approaches for the larger problems have been proposed to elucidate the problem. A mathematical model is developed for the unequal size facility layout problem with fixed flow between departments. We are considering the orientations of the departments with various sizes and aims to minimize the distance traveled by people, material, and other supporting services in the safest and most effective manner. Some of the constraints considered in the modeling are the restricted areas, reserved departmentry locations, and also the irregularity of the shapes of manufacturing layout. This paper focuses on the mathematical model and the solution of the non-quadratic assignment problem (non-QAP) by hybridizing the meta-h...
MATEMATIKA, 2018
Recently, oil refining industry is facing with lower profit margin due to uncertainty. This cause... more Recently, oil refining industry is facing with lower profit margin due to uncertainty. This causes oil refinery to include stochastic optimization in making a decision to maximize the profit. In the past, deterministic linear programming approach is widely used in oil refinery optimization problems. However, due to volatility and unpredictability of oil prices in the past ten years, deterministic model might not be able to predict the reality of the situation as it does not take into account the uncertainties thus, leads to non-optimal solution. Therefore, this study will develop two-stage stochastic linear programming for the midterm production planning of oil refinery to handle oil price volatility. Geometric Brownian motion (GBM) is used to describe uncertainties in crude oil price, petroleum product prices, and demand for petroleum products. This model generates the future realization of the price and demands with scenario tree based on the statistical specification of GBM using...
Journal of Physics: Conference Series, 2017
View the article online for updates and enhancements. Related content Meta-heuristic algorithm to... more View the article online for updates and enhancements. Related content Meta-heuristic algorithm to solve two-sided assembly line balancing problems A D Wirawan and A Maruf-Research on three-phase unbalanced distribution network reconfiguration strategy Shuang Hu, Ke-Jun Li, Yanshun Xu et al.-Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Journal of Physics: Conference Series, 2017
Now a day, several companies consider downsizing their distribution networks in ways that involve... more Now a day, several companies consider downsizing their distribution networks in ways that involve consolidation or phase-out of some of their current warehousing facilities due to the increasing competition, mounting cost pressure and taking advantage on the economies of scale. Consequently, the changes on economic situation after a certain period of time require an adjustment on the network model in order to get the optimal cost under the current economic conditions. This paper aimed to develop a mixed-integer linear programming model for a two-echelon warehouse network redesign problem with capacitated plant and uncapacitated warehouses. The main contribution of this study is considering capacity constraint for existing warehouses. A Simulated Annealing algorithm is proposed to tackle with the proposed model. The numerical solution showed the model and method of solution proposed was practical.
Indian Journal of Science and Technology, 2017
Traditionally, aircraft routing and crew pairing problems are solved sequentially with the aircra... more Traditionally, aircraft routing and crew pairing problems are solved sequentially with the aircraft routing problem solved first followed by the crew pairing problem. But in some cases, the results are suboptimal. In order to overcome this problem, both problems will be composed in one model. Although the integration model is challenging to solve but it is practically useful in airlines operations for getting the optimal solutions. In this study, we proposed the constructive heuristic method and the genetic algorithm (GA) in producing the feasible paths. After that, we will solve those two types of feasible paths in the integrated model by using three approaches which are the integer linear programming (ILP), Dantzig Wolfe decomposition method and Benders decomposition method. Computational results show that the obtained feasible path from the constructive heuristic method and solved by the Dantzig Wolfe decomposition method is more effective while the paths from the GA and solved by the Dantzig Wolfe decomposition method is good in finding the minimum computational time. From the results obtained, all the flight legs and crew pairing are used only once. There are four type of aircrafts are used in testing the performance of the approaches which based on local flights in Malaysia for seven days. The solutions of the feasible paths from GA is more advantageous in term of the computational times compare to the solutions by using the feasible paths from constructive heuristic method.
Indian Journal of Science and Technology, 2015
Background/Objectives: This paper focused on integrated Continuous Berth Allocation Problem (BAPC... more Background/Objectives: This paper focused on integrated Continuous Berth Allocation Problem (BAPC) and Quay Crane Scheduling Problem (QCSP) by considering non-crossing constraint to make it more realistic. Methods/Statistical analysis: Genetic Algorithm (GA) is a metaheuristic method that has been used extensively in Berth Allocation Problem (BAP). Crossover and mutation are selected as operators in this paper. Findings: The integrated model is formulated as a Mix Integer Problem (MIP) with the objective to minimize the sum of the processing times. A vessel's processing time is measured between arrival and departure includingwaiting time to be berthed and servicing time.The new algorithm of GA arecompatible with the integrated model and useful for finding near-optimal solutions. Three phase new algorithms of GA are proposed and provide a wider search to the solution space. Application/Improvements: Three phase of GA is another significant and promising variant of genetic algorithms in BAPC and QCSP. The probabilities of crossover and mutation determine the degree of solution accuracy and the convergence speed that GA canobtain. By using fixed values of crossover and mutation, the algorithm utilize the population information in each generation and adaptively adjust the crossover and mutation. So, the population diversity and sustain the convergence capacity is maintained.
2016 International Conference on Industrial Engineering, Management Science and Application (ICIMSA), 2016
This paper presents the simultaneous integration model of berth allocation and quay crane schedul... more This paper presents the simultaneous integration model of berth allocation and quay crane scheduling. Berths and quay cranes are both critical resources in port container terminals. The mathematical model uses a mixed integer linear programming with multiple objectives generated by considering various practical constraints. Small data instances have been taken to validate the integrated model. A numerical experiment was conducted by using LINGO programming software to evaluate the performance and to obtain the exact solution of the suggested model.
Recently, crude oil price becomes volatile and have been the popular issue to be discussed in eve... more Recently, crude oil price becomes volatile and have been the popular issue to be discussed in every country. Oil price fluctuations have major impact on the overall economy and finally will lead to increase in the inflation rate. It is important to describe these oil price fluctuations mathematically. This study aims to describe the above phenomena using geometric Brownian motion. Two crude oil prices, namely WTI and Brent have been analyzed based on daily oil price data from year 2000 until year 2015. Through the analysis using model assessment and model determination, crude oil price after year 2000 follows geometric Brownian motion process. We conclude that oil price fluctuations follow a geometric Brownian motion process without considering unexpected incidents.
Modern Applied Science, 2016
In airline operations planning, there are four problems which are schedule design, fleet assignme... more In airline operations planning, there are four problems which are schedule design, fleet assignment, aircraft routing and crew pairing problem. Those problems are sequentially and interdependent. Aircraft routing and crew pairing problem are hard to solve and normally crew pairing problem dependent to the aircraft routing problem which gives the suboptimal solutions. As minimizing the costs is important in the airline system, so in order to tackle suboptimal solutions, aircraft routing problem and crew pairing problem are being integrated in one model. For solving the integrated model, the feasible aircraft routes and crew pairs are required. Because of that, a method is being proposed in this work for generating the feasible aircraft routes and crew pairs which is the constructive heuristic method. By using the generic aircraft routes and crew pairs, the integrated model then being solve by two approaches. The first approach is the exact method called the integer linear programming...
Video communication over Vehicular Ad Hoc Networks (VANETs) has many applications, such as emerge... more Video communication over Vehicular Ad Hoc Networks (VANETs) has many applications, such as emergency video transmission, commercial advertisements and inter-vehicle digital entertainment. However, in urban vehicular scenario, delivering video streams to highly mobile vehicles is indeed a challenging task due to high radio interference, channel loss rate and burst packet losses. Thus, designing an error resilient scheme for reliable video geocasting in such harsh scenarios needs to be addressed. In this paper, we propose an error resilient scheme based on packet level Forward Error Correction (FEC) and interleaving technique for reliable video geocasting over VANET. The proposed scheme is able to adapt channel variations by using a Real Time Control Protocol (RTCP) report of vehicles within communication range of the video source. To achieve a fair comparison with other error protection schemes, we have implemented a proposed error resilient scheme in Network Simulator 2 (NS 2). The results of simulation based study show that the proposed scheme is able to improve perceived video quality and protection efficiency while minimizing bandwidth overhead (introduced by proactive error recovery) in urban vehicular scenarios
Network Protocols and Algorithms, 2013
A Vehicular Ad hoc Network (VANET) is a type of wireless ad hoc network that facilitates ubiquito... more A Vehicular Ad hoc Network (VANET) is a type of wireless ad hoc network that facilitates ubiquitous connectivity between vehicles in the absence of fixed infrastructure. Multi-hop routing and beaconing approaches are two important research challenges in high mobility vehicular networks. Routing protocols are divided into two categories of topology-based and position-based routing protocols. In this article, we perform a comparative study among the existing routing solutions, which explores the main advantages and drawbacks behind their design. After implementing the representatives of geographical and topology routing protocols, we analyze the simulation results and discuss the strengths and weaknesses of these routing protocols in regard to their suitability to vehicular networks. Lastly, we discuss the open issues and research directions related to VANET routing protocols.
In this research, an integrated approach is presented to simultaneously solve quay crane scheduli... more In this research, an integrated approach is presented to simultaneously solve quay crane scheduling and yard truck scheduling problems. A mathematical model was proposed considering the main real-world assumptions such as quay crane non-crossing, precedence constraints and variable berthing times for vessels with the aim of minimizing vessels completion time. Based on the numerical results, this proposed mathematical model has suitable efficiency for solving small instances. Two versions of imperialist competitive algorithm (ICA) are presented to heuristically solve the problem. The grouping version of algorithm (G-ICA) is used to solve the large-sized instances based on considering the allocation of trucks as a grouping problem. Effectiveness of the proposed metaheuristics on small-sized problems is compared with the optimal results of the mathematical model. In order to compare the efficiency of the proposed algorithms for large-sized instances, several instances were generated and solved, and the performance of algorithms has been compared with each other. Moreover, a simulated annealing (SA) algorithm is developed to solve the problem and evaluate the performance of the proposed ICA algorithms. Based on the experimental results, the G-ICA has a better performance compared to the ICA and SA. Also an instance of a container terminal in Iran has been investigated which shows that the proposed model and solution methods are applicable in real-world problems.