Dr. Parham Azimi is the university tutor at Faculty of Industrial and Mechanical Engineering in Islamic Azad University (Qazvin Branch) since 2004. Address: Iran, Tehran
Article history: Received 18 September 2014 Received in revised form 19 December 2014 Accepted 23... more Article history: Received 18 September 2014 Received in revised form 19 December 2014 Accepted 23 January 2015 Available online xxxx
Graceful labeling is one of the best known labeling methods of graphs. Despite the large number o... more Graceful labeling is one of the best known labeling methods of graphs. Despite the large number of papers published on the subject of graph labeling, there are few particular techniques to be used by researchers to gracefully label graphs. In this paper, first a new approach based on the mathematical programming technique is presented to model the graceful labeling problem. Then a “branching method” is developed to solve the problem for special classes of graphs. Computational results show the efficiency of the proposed algorithm for different classes of graphs. One of the interesting results of our model is in the class of trees. The largest tree known to be graceful has at most 27 vertices but our model can easily solve the graceful labeling for trees with 40 vertices.
World Academy of Science, Engineering and Technology, International Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing Engineering, 2012
In this research, we have developed a new efficient heuristic algorithm for the dynamic facility ... more In this research, we have developed a new efficient heuristic algorithm for the dynamic facility layout problem with budget constraint (DFLPB). This heuristic algorithm combines two mathematical programming methods such as discrete event simulation and linear integer programming (IP) to obtain a near optimum solution. In the proposed algorithm, the non-linear model of the DFLP has been changed to a pure integer programming (PIP) model. Then, the optimal solution of the PIP model has been used in a simulation model that has been designed in a similar manner as the DFLP for determining the probability of assigning a facility to a location. After a sufficient number of runs, the simulation model obtains near optimum solutions. Finally, to verify the performance of the algorithm, several test problems have been solved. The results show that the proposed algorithm is more efficient in terms of speed and accuracy than other heuristic algorithms presented in previous works found in the lit...
Cross docking is one of the innovation product distribution strategies for transhipment of time-s... more Cross docking is one of the innovation product distribution strategies for transhipment of time-sensitive products in distribution centers which has absorbed a lot of attention in the last 10 years. The current study develops a new concept named on-line docking" in an actual container port which is the main contribution of the research. In the model, some previous simpli cations were removed from the model using optimization via simulation technique, and also new decision variables were introduced to control the system. The objective function is to minimize the average annual system costs by assigning the best number of inbound-outbound docks and the fleet size for the internal transportations. To do so, all information was taken from an actual container port system and the model was built in the simulation software and then it was optimized via a meta-heuristic algorithm. The computational results show the effciency of the proposed approach in real world applications.
Journal of Optimization in Industrial Engineering, 2019
In this research, a hierarchical location-allocation problem is modeled in a queue framework. The... more In this research, a hierarchical location-allocation problem is modeled in a queue framework. The queue model is considered as M/M/1/k, in which system capacity is finite, equals to k. This is the main contribution of the current research. Customer's enters to the system in order to find the service according to a Poisson. In this problem, the hierarchical location-allocation model is considered in two levels. Also, the model has two objective functions: maximizing the total number of demand coverage and minimizing the waiting time of customers in queues to receive services. After modeling and verifying the validity of the presented model, it is solved using NSGA II and MOPSO meta-heuristics.
In this paper, several pickup/delivery and pickup/dispatching rules have been examined in an auto... more In this paper, several pickup/delivery and pickup/dispatching rules have been examined in an automated guided vehicle system which is the biggest set of strategies in the literature. The best control strategy has been determined considering some important criteria such as System Throughput(ST), Mean Flow Time of Parts (MFTP), Mean Tardiness of Parts (MFTP), AGV Idle Time (AGVIT), AGV Travel Full (AGVTF), AGV Travel Empty (AGVTE), AGV Load Time (AGVLT), AGV Unload Time (AGVUT), Mean Queue Length (MQL) and Mean Queue Waiting (MQW). All strategies have been ranked using SAW, VICOR and TOPSIS methods. For this reason, several simulation experiments were conducted to obtain the best solution. As the experimental results show the approach is effective enough to be used in real world environments.
However, there is a lot of capital and plenty of manpower in the auto spare part industry, the en... more However, there is a lot of capital and plenty of manpower in the auto spare part industry, the enterprises and supply chains of this industry do not perform well in our country. This research models a three-level supply chain with multiple manufacturers, distribution centers and retailers, to minimize the total cost by taking into account various disruptions. The database of two active car spare parts companies for five strategic products in one year has been used. Then, the mathematical model is analyzed by considering disruptions based on three different sales policies: back orders, lost sales and outsourcing. Besides, to evaluate the performance of the model some numerical examples are used and analyzed to determine that algorithm works. Model solved efficiently by MATLAB software. The results show that the proposed algorithm of this research can neutralize the effect of the disruptions and cause a significant reduction in total cost of the system. The model is useful for helping...
Journal of Optimization in Industrial Engineering, 2011
The dramatic increasing of sea-freight container transportations and the developing trend for usi... more The dramatic increasing of sea-freight container transportations and the developing trend for using containers in the multimodal handling systems through the sea, rail, road and land in the present market cause some challenges to the general managers of container terminals such as increasing demand, competitive situation, new investments and expansion of new activities and the need to use new methods to fulfil effective operations both along quayside and within the yard. Among these issues, minimizing the turnaround time of vessels is considered to be the first aim of every container port system. Regarding the complex structure of container ports, this paper presents a simulation model that calculates the number of trucks needed in Shahid Rajaee Container Port for handling containers between the berth and the yard. In this research, some important criteria such as vessel turnaround time, gantry crane utilization and truck utilization have been considered. By analyzing the results of...
Nowadays, there are different leadership styles in different organizations that depend on that or... more Nowadays, there are different leadership styles in different organizations that depend on that organization management and which styles are used for guidance and leadership. The most important leadership styles in large organizations that are used for are such as imperative, advisory, collaborative and compassionate styles. Leadership style can affect on the staffs job stress conditions. In this research,we are seeking for the effects of different leadership styles on job stress. For reaching this relationship, different kinds of leadership styles were measured by a questionnaire in one of the regions of national oil products distribution company. On the other, we used standard questionnaires for measuring job stress that Cronbach's alpha was used for evaluating the validity of these two questionnaires. For statistical analyze, we used hypothesis test, Spearman correlation coefficient and multiple regression with repeated entering. The results showed that: There is significant r...
The dramatic increasing of sea-freight container transportations and the developing trends for us... more The dramatic increasing of sea-freight container transportations and the developing trends for using containers in the multimodal handling systems through the sea, rail, road and land in nowadays market cause general managers of container terminals to face challenges such as increasing demand, competitive situation, new investments and expansion of new activities and need to use new methods to fulfil effective operations both along quayside and within the yard. Among these issues, minimizing the turnaround time of vessels is considered to be the first aim of every container port system. Regarding the complex structure of container ports, this paper presents a simulation model that calculates the number of trucks needed in the Iranian Shahid Rajaee Container Port for handling containers between the berth and the yard. In this research, some important criteria such as vessel turnaround time, gantry crane utilization and truck utilization have been considered. By analyzing the results ...
This research is conducted to investigate the problem of locating the trauma centers and helicopt... more This research is conducted to investigate the problem of locating the trauma centers and helicopters’ station in order to optimize the trauma care system. The stochastic characteristics of the system, such as stochastic transferring time of the patients, stochastic demand and stochastic servicing time of the patients in trauma centers are taken into account. The problem is first modeled as a stochastic mixed-integer linear mathematical model. In the proposed model, minimizing the total cost, minimizing the transferring time, and minimizing the waiting time inside the trauma center are considered as the three separate objectives. The third objective cannot be expressed by an analytical expression because of the complexity inside a trauma center. Therefore, an artificial neural network (ANN) is first trained by a simulation model and then is utilized to estimate the third objective function. A hybrid multi-objective algorithm is developed based on a non-dominated sorting water flow algorithm in order to search the solution space. Different numerical examples are applied to study the performance of the proposed method. The computational results show that the combination of simulation, ANN, and optimization technique provides an effective means for the highly complex optimization problems.
The cost of semi-finished products storage and processing time are two issues affecting the rate ... more The cost of semi-finished products storage and processing time are two issues affecting the rate of manufacturing in all production systems. The acceleration in production time is usually associated with the increase of costs and lack of appropriate allocation of the production line buffers imposing production costs and increase in delivery time and decrease in productivity. Many previous studies have focused on deterministic production systems using mathematical programming models. Moreover, the optimization of buffers and processing times with stochastic events has not been considered simultaneously. In this study, a new simulation-based optimization model has been proposed to address the modeling and solving of buffer and processing time optimization problem in a stochastic environment. The real world problem has been modeled by using the simulation technique and the model replicated by a design of experiment method. The results were used to build a meta-model of regression for the objective functions and finally, a new mathematical model was solved by a multiobjective Genetic Algorithm. The results of this research show that the proposed approach has efficient solutions and could be easily applied to real world problems.
Abstract The redundancy allocation problem (RAP) is a useful method to enhance system reliability... more Abstract The redundancy allocation problem (RAP) is a useful method to enhance system reliability. In most works involving RAP, failure rates of the system components are assumed to follow either exponential or k-Erlang distributions. In real world problems however, many systems have components with increasing failure rates. This indicates that as time passes by, the failure rates of the system components increase in comparison to their initial failure rates. In this paper, the redundancy allocation problem of a series–parallel system with components having an increasing failure rate based on Weibull distribution is investigated. An optimization method via simulation is proposed for modeling and a genetic algorithm is developed to solve the problem.
Article history: Received 18 September 2014 Received in revised form 19 December 2014 Accepted 23... more Article history: Received 18 September 2014 Received in revised form 19 December 2014 Accepted 23 January 2015 Available online xxxx
Graceful labeling is one of the best known labeling methods of graphs. Despite the large number o... more Graceful labeling is one of the best known labeling methods of graphs. Despite the large number of papers published on the subject of graph labeling, there are few particular techniques to be used by researchers to gracefully label graphs. In this paper, first a new approach based on the mathematical programming technique is presented to model the graceful labeling problem. Then a “branching method” is developed to solve the problem for special classes of graphs. Computational results show the efficiency of the proposed algorithm for different classes of graphs. One of the interesting results of our model is in the class of trees. The largest tree known to be graceful has at most 27 vertices but our model can easily solve the graceful labeling for trees with 40 vertices.
World Academy of Science, Engineering and Technology, International Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing Engineering, 2012
In this research, we have developed a new efficient heuristic algorithm for the dynamic facility ... more In this research, we have developed a new efficient heuristic algorithm for the dynamic facility layout problem with budget constraint (DFLPB). This heuristic algorithm combines two mathematical programming methods such as discrete event simulation and linear integer programming (IP) to obtain a near optimum solution. In the proposed algorithm, the non-linear model of the DFLP has been changed to a pure integer programming (PIP) model. Then, the optimal solution of the PIP model has been used in a simulation model that has been designed in a similar manner as the DFLP for determining the probability of assigning a facility to a location. After a sufficient number of runs, the simulation model obtains near optimum solutions. Finally, to verify the performance of the algorithm, several test problems have been solved. The results show that the proposed algorithm is more efficient in terms of speed and accuracy than other heuristic algorithms presented in previous works found in the lit...
Cross docking is one of the innovation product distribution strategies for transhipment of time-s... more Cross docking is one of the innovation product distribution strategies for transhipment of time-sensitive products in distribution centers which has absorbed a lot of attention in the last 10 years. The current study develops a new concept named on-line docking" in an actual container port which is the main contribution of the research. In the model, some previous simpli cations were removed from the model using optimization via simulation technique, and also new decision variables were introduced to control the system. The objective function is to minimize the average annual system costs by assigning the best number of inbound-outbound docks and the fleet size for the internal transportations. To do so, all information was taken from an actual container port system and the model was built in the simulation software and then it was optimized via a meta-heuristic algorithm. The computational results show the effciency of the proposed approach in real world applications.
Journal of Optimization in Industrial Engineering, 2019
In this research, a hierarchical location-allocation problem is modeled in a queue framework. The... more In this research, a hierarchical location-allocation problem is modeled in a queue framework. The queue model is considered as M/M/1/k, in which system capacity is finite, equals to k. This is the main contribution of the current research. Customer's enters to the system in order to find the service according to a Poisson. In this problem, the hierarchical location-allocation model is considered in two levels. Also, the model has two objective functions: maximizing the total number of demand coverage and minimizing the waiting time of customers in queues to receive services. After modeling and verifying the validity of the presented model, it is solved using NSGA II and MOPSO meta-heuristics.
In this paper, several pickup/delivery and pickup/dispatching rules have been examined in an auto... more In this paper, several pickup/delivery and pickup/dispatching rules have been examined in an automated guided vehicle system which is the biggest set of strategies in the literature. The best control strategy has been determined considering some important criteria such as System Throughput(ST), Mean Flow Time of Parts (MFTP), Mean Tardiness of Parts (MFTP), AGV Idle Time (AGVIT), AGV Travel Full (AGVTF), AGV Travel Empty (AGVTE), AGV Load Time (AGVLT), AGV Unload Time (AGVUT), Mean Queue Length (MQL) and Mean Queue Waiting (MQW). All strategies have been ranked using SAW, VICOR and TOPSIS methods. For this reason, several simulation experiments were conducted to obtain the best solution. As the experimental results show the approach is effective enough to be used in real world environments.
However, there is a lot of capital and plenty of manpower in the auto spare part industry, the en... more However, there is a lot of capital and plenty of manpower in the auto spare part industry, the enterprises and supply chains of this industry do not perform well in our country. This research models a three-level supply chain with multiple manufacturers, distribution centers and retailers, to minimize the total cost by taking into account various disruptions. The database of two active car spare parts companies for five strategic products in one year has been used. Then, the mathematical model is analyzed by considering disruptions based on three different sales policies: back orders, lost sales and outsourcing. Besides, to evaluate the performance of the model some numerical examples are used and analyzed to determine that algorithm works. Model solved efficiently by MATLAB software. The results show that the proposed algorithm of this research can neutralize the effect of the disruptions and cause a significant reduction in total cost of the system. The model is useful for helping...
Journal of Optimization in Industrial Engineering, 2011
The dramatic increasing of sea-freight container transportations and the developing trend for usi... more The dramatic increasing of sea-freight container transportations and the developing trend for using containers in the multimodal handling systems through the sea, rail, road and land in the present market cause some challenges to the general managers of container terminals such as increasing demand, competitive situation, new investments and expansion of new activities and the need to use new methods to fulfil effective operations both along quayside and within the yard. Among these issues, minimizing the turnaround time of vessels is considered to be the first aim of every container port system. Regarding the complex structure of container ports, this paper presents a simulation model that calculates the number of trucks needed in Shahid Rajaee Container Port for handling containers between the berth and the yard. In this research, some important criteria such as vessel turnaround time, gantry crane utilization and truck utilization have been considered. By analyzing the results of...
Nowadays, there are different leadership styles in different organizations that depend on that or... more Nowadays, there are different leadership styles in different organizations that depend on that organization management and which styles are used for guidance and leadership. The most important leadership styles in large organizations that are used for are such as imperative, advisory, collaborative and compassionate styles. Leadership style can affect on the staffs job stress conditions. In this research,we are seeking for the effects of different leadership styles on job stress. For reaching this relationship, different kinds of leadership styles were measured by a questionnaire in one of the regions of national oil products distribution company. On the other, we used standard questionnaires for measuring job stress that Cronbach's alpha was used for evaluating the validity of these two questionnaires. For statistical analyze, we used hypothesis test, Spearman correlation coefficient and multiple regression with repeated entering. The results showed that: There is significant r...
The dramatic increasing of sea-freight container transportations and the developing trends for us... more The dramatic increasing of sea-freight container transportations and the developing trends for using containers in the multimodal handling systems through the sea, rail, road and land in nowadays market cause general managers of container terminals to face challenges such as increasing demand, competitive situation, new investments and expansion of new activities and need to use new methods to fulfil effective operations both along quayside and within the yard. Among these issues, minimizing the turnaround time of vessels is considered to be the first aim of every container port system. Regarding the complex structure of container ports, this paper presents a simulation model that calculates the number of trucks needed in the Iranian Shahid Rajaee Container Port for handling containers between the berth and the yard. In this research, some important criteria such as vessel turnaround time, gantry crane utilization and truck utilization have been considered. By analyzing the results ...
This research is conducted to investigate the problem of locating the trauma centers and helicopt... more This research is conducted to investigate the problem of locating the trauma centers and helicopters’ station in order to optimize the trauma care system. The stochastic characteristics of the system, such as stochastic transferring time of the patients, stochastic demand and stochastic servicing time of the patients in trauma centers are taken into account. The problem is first modeled as a stochastic mixed-integer linear mathematical model. In the proposed model, minimizing the total cost, minimizing the transferring time, and minimizing the waiting time inside the trauma center are considered as the three separate objectives. The third objective cannot be expressed by an analytical expression because of the complexity inside a trauma center. Therefore, an artificial neural network (ANN) is first trained by a simulation model and then is utilized to estimate the third objective function. A hybrid multi-objective algorithm is developed based on a non-dominated sorting water flow algorithm in order to search the solution space. Different numerical examples are applied to study the performance of the proposed method. The computational results show that the combination of simulation, ANN, and optimization technique provides an effective means for the highly complex optimization problems.
The cost of semi-finished products storage and processing time are two issues affecting the rate ... more The cost of semi-finished products storage and processing time are two issues affecting the rate of manufacturing in all production systems. The acceleration in production time is usually associated with the increase of costs and lack of appropriate allocation of the production line buffers imposing production costs and increase in delivery time and decrease in productivity. Many previous studies have focused on deterministic production systems using mathematical programming models. Moreover, the optimization of buffers and processing times with stochastic events has not been considered simultaneously. In this study, a new simulation-based optimization model has been proposed to address the modeling and solving of buffer and processing time optimization problem in a stochastic environment. The real world problem has been modeled by using the simulation technique and the model replicated by a design of experiment method. The results were used to build a meta-model of regression for the objective functions and finally, a new mathematical model was solved by a multiobjective Genetic Algorithm. The results of this research show that the proposed approach has efficient solutions and could be easily applied to real world problems.
Abstract The redundancy allocation problem (RAP) is a useful method to enhance system reliability... more Abstract The redundancy allocation problem (RAP) is a useful method to enhance system reliability. In most works involving RAP, failure rates of the system components are assumed to follow either exponential or k-Erlang distributions. In real world problems however, many systems have components with increasing failure rates. This indicates that as time passes by, the failure rates of the system components increase in comparison to their initial failure rates. In this paper, the redundancy allocation problem of a series–parallel system with components having an increasing failure rate based on Weibull distribution is investigated. An optimization method via simulation is proposed for modeling and a genetic algorithm is developed to solve the problem.
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Papers by Dr Parham Azimi