Scholars, practitioners, and students in operations research and management science (OR/MS) often... more Scholars, practitioners, and students in operations research and management science (OR/MS) often hesitate to use traditional approaches to evaluate journal quality because of the inconsistency of these approaches to perceptions and other associated biases. We introduce an alternative approach, which is based on Google's PageRank, to evaluate 31 OR/MS journals. This approach enhances the impact factor method by considering both citation quantity and quality. When we apply our method to OR/MS journals, the results match survey opinions and significantly outperform rankings based on impact factors. In addition, we provide an extensive discussion of other methods that have been used to assess journal quality. Compared to these methods, our method is better able to discern quality differences for journals that are perceived to be of relatively higher quality. Most importantly, we integrate our method into a Web-based journal-ranking system.
Practise is one of the most important steps in learning the art of computer programming. Unfortun... more Practise is one of the most important steps in learning the art of computer programming. Unfortunately, human grading of programming assignments is a tedious and error-prone task, a problem compounded by the large enrolments of many programming courses. As a result, students in such courses tend to be given fewer programming assignments than should be ideally given. One solution to this problem is to automate the grading process such that students can electronically submit their programming assignments and receive instant feedback. This paper studies the implementation of one such automated grading system, called the Online Judge, in the School of Computing of the National University of Singapore for a compulsory first-year course that teaches basic programming techniques with over 700 students, describing the student reactions and behavior as well as the difficulties encountered. The Online Judge was also successfully employed for an advanced undergraduate course and an introductory high school course.
International Transactions in Operational Research, 2014
In this paper, we present an efficient intelligent search algorithm for the two‐dimensional recta... more In this paper, we present an efficient intelligent search algorithm for the two‐dimensional rectangular strip packing problem. This algorithm involves three stages, namely greedy selection, local improvement, and randomized improvement. The greedy selection stage provides a good initial solution for the local improvement stage, which then tries to improve the solution by a deterministic local search. The randomized improvement stage employs a simple randomized local search process, which does not need any control parameter. Each of these three stages uses a heuristic approach to construct solutions based on an improved scoring rule and the least‐waste‐first strategy. Extensive experiments show that, to the best of our knowledge, our proposed algorithm performs slightly better than all previously published metaheuristics for most of the benchmark instances.
a b s t r a c t In this paper, we examine the two-dimensional variable-sized bin packing problem ... more a b s t r a c t In this paper, we examine the two-dimensional variable-sized bin packing problem (2DVSBPP), where the task is to pack all given rectangles into bins of various sizes such that the total area of the used bins is minimized. We partition the search space of the 2DVSBPP into sets and impose an order on the sets, and then use a goal-driven approach to take advantage of the special structure of this partitioned solution space. Since the 2DVSBPP is a generalization of the two-dimensional bin packing problem (2DBPP), our approach can be adapted to the 2DBPP with minimal changes. Computational experiments on the stan-dard benchmark data for both the 2DVSBPP and 2DBPP shows that our approach is more effective than existing approaches in literature. Ó 2012 Elsevier B.V. All rights reserved.
... 3 Existing Approaches Kim and Hong [4] described a standard branch and bound algorithm for th... more ... 3 Existing Approaches Kim and Hong [4] described a standard branch and bound algorithm for the restricted variant that can optimally solve instances of up to 5 stacks by 5 tiers within 4 minutes, but is too slow for practical use for larger instances. ... Kim et al. ...
Practise is one of the most important steps in learning the art of computer programming. Unfortun... more Practise is one of the most important steps in learning the art of computer programming. Unfortunately, human grading of programming assignments is a tedious and error-prone task, a problem compounded by the large enrolments of many programming courses. As a result, students in such courses tend to be given fewer programming assignments than should be ideally given. One solution to this problem is to automate the grading process such that students can electronically submit their programming assignments and receive instant feedback. This paper studies the implementation of one such automated grading system, called the Online Judge, in the School of Computing of the National University of Singapore for a com-pulsory first-year course that teaches basic programming techniques with over 700 students, describing the student reactions and behavior as well as the difficulties encountered. The Online Judge was also success-fully employed for an advanced undergraduate course and an introduct...
This study uses several quantitative techniques to enable a multidimensional analysis of 47 key b... more This study uses several quantitative techniques to enable a multidimensional analysis of 47 key business journals by analyzing the scientific communication patterns and structural influences of these journals. Apart from using clustering techniques to establish research clusters in the Business domain, we apply a refined PageRank method by differentiating between the citation types to enable a cross-sectional evaluation of the selected journals. The results indicate that the five most influential journals are from Finance and Economics. The selected Finance journals are knowledge hubs and the selected Economics journals are knowledge sources when ISI's entire journal database is considered. However, within the Business domain, the selected Finance journals appear to be high impact knowledge hubs while the selected Economics journals appear to be high impact journals despite weak citation activity. All in all, such analyses are beneficial to scholars when selecting publication outlets to showcase their research, and to agencies such Financial Times and Bloomberg when selecting their journals basket for their annual journal evaluation exercises.
Journal of the Association for Information Science and Technology, 2014
In this article, the authors introduce two citation‐based approaches to facilitate a multidimensi... more In this article, the authors introduce two citation‐based approaches to facilitate a multidimensional evaluation of 39 selected management journals. The first is a refined application of PageRank via the differentiation of citation types. The second is a form of mathematical manipulation to identify the roles that the selected management journals play. Their findings reveal that Academy of Management Journal, Academy of Management Review, and Administrative Science Quarterly are the top three management journals, respectively. They also discovered that these three journals play the role of a knowledge hub in the domain. Finally, when compared with Journal Citation Reports (Thomson Reuters, Philadelphia, PA), their results closely match expert opinions.
ABSTRACT The purpose of this research is to furnish the OR/MS research community with an updated ... more ABSTRACT The purpose of this research is to furnish the OR/MS research community with an updated assessment of the discipline's journals set with refinements that also highlight the various characteristics of OR/MS journals. More specifically, we apply a refined PageRank method initially proposed by Xu et al. (2011) to evaluate the top 31 OR/MS journals for 2010, and report our findings. We also report the shifts in the rankings that span 5 years, from 2006 to 2010. We observe that Manufacturing and Service Operations Management, indexed by the SCI only in 2008, is a specialized journal that is consistently highly regarded within the discipline. The rankings also suggest that Management Science is more established as a generalized journal as it has more external impact. In general, our ranking results correlate with expert opinions, and we also observe, report and discuss some interesting patterns that have emerged over the past 5 years from 2006 to 2010.
In this article, we study the joint pricing and inventory control problem for perishables when a ... more In this article, we study the joint pricing and inventory control problem for perishables when a retailer does not sell new and old inventory at the same time. At the beginning of a period, the retailer makes replenishment and pricing decisions, and at the end of a period, the retailer decides whether to dispose of ending inventory or carry it forward to the next period. The objective of the retailer is to maximize the long‐run average profit. Assuming zero lead time, we propose an efficient solution approach to the problem, which is also generalized to solve three extensions to the basic model. A feature of the present study is that we consider explicitly the influence of perishability on the demand. Among the insights gathered from the numerical analysis, we find that dynamic pricing aids extending shelf life and when disposal incurs a lower cost, or even a positive salvage value, the retailer is induced to dispose earlier since the benefit of selling new inventory offsets the los...
International Journal of Computer Applications in Technology, 2005
Given the imbalances of an international shipping company's empty containers in ports all over th... more Given the imbalances of an international shipping company's empty containers in ports all over the world, we study the problem of the dynamic distribution of empty containers with and without third party leasing from another company and develop a decision support system to solve the empty container distribution problem.
Scholars, practitioners, and students in operations research and management science (OR/MS) often... more Scholars, practitioners, and students in operations research and management science (OR/MS) often hesitate to use traditional approaches to evaluate journal quality because of the inconsistency of these approaches to perceptions and other associated biases. We introduce an alternative approach, which is based on Google's PageRank, to evaluate 31 OR/MS journals. This approach enhances the impact factor method by considering both citation quantity and quality. When we apply our method to OR/MS journals, the results match survey opinions and significantly outperform rankings based on impact factors. In addition, we provide an extensive discussion of other methods that have been used to assess journal quality. Compared to these methods, our method is better able to discern quality differences for journals that are perceived to be of relatively higher quality. Most importantly, we integrate our method into a Web-based journal-ranking system.
We extend the traveling salesman problem with pickup and delivery and LIFO loading (TSPPDL) by co... more We extend the traveling salesman problem with pickup and delivery and LIFO loading (TSPPDL) by considering two additional factors, namely the use of multiple vehicles and a limitation on the total distance that a vehicle can travel; both of these factors occur commonly in practice. We call the resultant problem the multiple pickup and delivery traveling salesman problem with LIFO loading and distance constraints (MTSPPD-LD). This paper presents a thorough preliminary investigation of the MTSPPD-LD. We propose six new neighborhood operators for the problem that can be used in search heuristics or meta-heuristics. We also devise a two-stage approach for solving the problem, where the first stage focuses on minimizing the number of vehicles required and the second stage minimizes the total travel distance. We consider two possible approaches for the first stage (simulated annealing and ejection pool) and two for the second stage (variable neighborhood search and probabilistic tabu search). Our computational results serve as benchmarks for future researchers on the problem.
Hospitals need to repeatedly produce duty rosters for its nursing staff. The good scheduling of n... more Hospitals need to repeatedly produce duty rosters for its nursing staff. The good scheduling of nurses has impact on the quality of health care, the recruitment of nurses, the development of budgets and other nursing functions. The nurse rostering problem (NRP) has been the subject of much study. This paper presents a brief overview, in the form of a bibliographic survey, of the many models and methodologies available to solve the NRP.
In the capacitated team orienteering problem (CTOP), we are given a set of homogeneous vehicles a... more In the capacitated team orienteering problem (CTOP), we are given a set of homogeneous vehicles and a set of customers each with a service demand value and a profit value. A vehicle can get the profit of a customer by satisfying its demand, but the total demand of all customers in its route cannot exceed the vehicle capacity and the length of the route must be within a specified maximum. The problem is to design a set of routes that maximizes the total profit collected by the vehicles. In this article, we propose a new heuristic algorithm for the CTOP using the ejection pool framework with an adaptive strategy and a diversification mechanism based on toggling between two priority rules. Experimental results show that our algorithm can match or improve all the best known results on the standard CTOP benchmark instances proposed by Archetti et al. (2008).
In this paper, we extend upon current research in the vehicle routing problem whereby labour regu... more In this paper, we extend upon current research in the vehicle routing problem whereby labour regulations affect planning horizons, and therefore, profitability. We call this extension the multiperiod vehicle routing problem with profit (mVRPP). The goal is to determine routes for a set of vehicles that maximizes profitability from visited locations, based on the conditions that vehicles can only travel during stipulated working hours within each period in a given planning horizon and that the vehicles are only required to return to the depot at the end of the last period. We propose an effective memetic algorithm with a gianttour representation to solve the mVRPP. To efficiently evaluate a chromosome, we develop a greedy procedure to partition a given giant-tour into individual routes, and prove that the resultant partition is optimal. We evaluate the effectiveness of our memetic algorithm with extensive experiments based on a set of modified benchmark instances. The results indicate that our approach generates high-quality solutions that are reasonably close to the best known solutions or proven optima, and significantly better than the solutions obtained using heuristics employed by professional schedulers.
Practise is one of the most important steps in learning the art of computer programming. Unfortun... more Practise is one of the most important steps in learning the art of computer programming. Unfortunately, human grading of programming assignments is a tedious and error-prone task, a problem compounded by the large enrolments of many programming courses. As a result, students in such courses tend to be given fewer programming assignments than should be ideally given. One solution to this problem is to automate the grading process such that students can electronically submit their programming assignments and receive instant feedback. This paper studies the implementation of one such automated grading system, called the Online Judge, in the School of Computing of the National University of Singapore for a compulsory first-year course that teaches basic programming techniques with over 700 students, describing the student reactions and behavior as well as the difficulties encountered. The Online Judge was also successfully employed for an advanced undergraduate course and an introductory high school course.
This report describes and evaluates the implementation and applicability of an automatic programm... more This report describes and evaluates the implementation and applicability of an automatic programming assignment grading system we named the online judge. We compared this with the manual grading system that is currently being used and showed that the automatic grading system, when implemented carefully, is more convenient, fairer, and more secure than the former. We have successfully tested the system on two courses. However, further studies need to be conducted to improve the effectiveness of learning through this system.
Scholars, practitioners, and students in operations research and management science (OR/MS) often... more Scholars, practitioners, and students in operations research and management science (OR/MS) often hesitate to use traditional approaches to evaluate journal quality because of the inconsistency of these approaches to perceptions and other associated biases. We introduce an alternative approach, which is based on Google's PageRank, to evaluate 31 OR/MS journals. This approach enhances the impact factor method by considering both citation quantity and quality. When we apply our method to OR/MS journals, the results match survey opinions and significantly outperform rankings based on impact factors. In addition, we provide an extensive discussion of other methods that have been used to assess journal quality. Compared to these methods, our method is better able to discern quality differences for journals that are perceived to be of relatively higher quality. Most importantly, we integrate our method into a Web-based journal-ranking system.
Practise is one of the most important steps in learning the art of computer programming. Unfortun... more Practise is one of the most important steps in learning the art of computer programming. Unfortunately, human grading of programming assignments is a tedious and error-prone task, a problem compounded by the large enrolments of many programming courses. As a result, students in such courses tend to be given fewer programming assignments than should be ideally given. One solution to this problem is to automate the grading process such that students can electronically submit their programming assignments and receive instant feedback. This paper studies the implementation of one such automated grading system, called the Online Judge, in the School of Computing of the National University of Singapore for a compulsory first-year course that teaches basic programming techniques with over 700 students, describing the student reactions and behavior as well as the difficulties encountered. The Online Judge was also successfully employed for an advanced undergraduate course and an introductory high school course.
International Transactions in Operational Research, 2014
In this paper, we present an efficient intelligent search algorithm for the two‐dimensional recta... more In this paper, we present an efficient intelligent search algorithm for the two‐dimensional rectangular strip packing problem. This algorithm involves three stages, namely greedy selection, local improvement, and randomized improvement. The greedy selection stage provides a good initial solution for the local improvement stage, which then tries to improve the solution by a deterministic local search. The randomized improvement stage employs a simple randomized local search process, which does not need any control parameter. Each of these three stages uses a heuristic approach to construct solutions based on an improved scoring rule and the least‐waste‐first strategy. Extensive experiments show that, to the best of our knowledge, our proposed algorithm performs slightly better than all previously published metaheuristics for most of the benchmark instances.
a b s t r a c t In this paper, we examine the two-dimensional variable-sized bin packing problem ... more a b s t r a c t In this paper, we examine the two-dimensional variable-sized bin packing problem (2DVSBPP), where the task is to pack all given rectangles into bins of various sizes such that the total area of the used bins is minimized. We partition the search space of the 2DVSBPP into sets and impose an order on the sets, and then use a goal-driven approach to take advantage of the special structure of this partitioned solution space. Since the 2DVSBPP is a generalization of the two-dimensional bin packing problem (2DBPP), our approach can be adapted to the 2DBPP with minimal changes. Computational experiments on the stan-dard benchmark data for both the 2DVSBPP and 2DBPP shows that our approach is more effective than existing approaches in literature. Ó 2012 Elsevier B.V. All rights reserved.
... 3 Existing Approaches Kim and Hong [4] described a standard branch and bound algorithm for th... more ... 3 Existing Approaches Kim and Hong [4] described a standard branch and bound algorithm for the restricted variant that can optimally solve instances of up to 5 stacks by 5 tiers within 4 minutes, but is too slow for practical use for larger instances. ... Kim et al. ...
Practise is one of the most important steps in learning the art of computer programming. Unfortun... more Practise is one of the most important steps in learning the art of computer programming. Unfortunately, human grading of programming assignments is a tedious and error-prone task, a problem compounded by the large enrolments of many programming courses. As a result, students in such courses tend to be given fewer programming assignments than should be ideally given. One solution to this problem is to automate the grading process such that students can electronically submit their programming assignments and receive instant feedback. This paper studies the implementation of one such automated grading system, called the Online Judge, in the School of Computing of the National University of Singapore for a com-pulsory first-year course that teaches basic programming techniques with over 700 students, describing the student reactions and behavior as well as the difficulties encountered. The Online Judge was also success-fully employed for an advanced undergraduate course and an introduct...
This study uses several quantitative techniques to enable a multidimensional analysis of 47 key b... more This study uses several quantitative techniques to enable a multidimensional analysis of 47 key business journals by analyzing the scientific communication patterns and structural influences of these journals. Apart from using clustering techniques to establish research clusters in the Business domain, we apply a refined PageRank method by differentiating between the citation types to enable a cross-sectional evaluation of the selected journals. The results indicate that the five most influential journals are from Finance and Economics. The selected Finance journals are knowledge hubs and the selected Economics journals are knowledge sources when ISI's entire journal database is considered. However, within the Business domain, the selected Finance journals appear to be high impact knowledge hubs while the selected Economics journals appear to be high impact journals despite weak citation activity. All in all, such analyses are beneficial to scholars when selecting publication outlets to showcase their research, and to agencies such Financial Times and Bloomberg when selecting their journals basket for their annual journal evaluation exercises.
Journal of the Association for Information Science and Technology, 2014
In this article, the authors introduce two citation‐based approaches to facilitate a multidimensi... more In this article, the authors introduce two citation‐based approaches to facilitate a multidimensional evaluation of 39 selected management journals. The first is a refined application of PageRank via the differentiation of citation types. The second is a form of mathematical manipulation to identify the roles that the selected management journals play. Their findings reveal that Academy of Management Journal, Academy of Management Review, and Administrative Science Quarterly are the top three management journals, respectively. They also discovered that these three journals play the role of a knowledge hub in the domain. Finally, when compared with Journal Citation Reports (Thomson Reuters, Philadelphia, PA), their results closely match expert opinions.
ABSTRACT The purpose of this research is to furnish the OR/MS research community with an updated ... more ABSTRACT The purpose of this research is to furnish the OR/MS research community with an updated assessment of the discipline's journals set with refinements that also highlight the various characteristics of OR/MS journals. More specifically, we apply a refined PageRank method initially proposed by Xu et al. (2011) to evaluate the top 31 OR/MS journals for 2010, and report our findings. We also report the shifts in the rankings that span 5 years, from 2006 to 2010. We observe that Manufacturing and Service Operations Management, indexed by the SCI only in 2008, is a specialized journal that is consistently highly regarded within the discipline. The rankings also suggest that Management Science is more established as a generalized journal as it has more external impact. In general, our ranking results correlate with expert opinions, and we also observe, report and discuss some interesting patterns that have emerged over the past 5 years from 2006 to 2010.
In this article, we study the joint pricing and inventory control problem for perishables when a ... more In this article, we study the joint pricing and inventory control problem for perishables when a retailer does not sell new and old inventory at the same time. At the beginning of a period, the retailer makes replenishment and pricing decisions, and at the end of a period, the retailer decides whether to dispose of ending inventory or carry it forward to the next period. The objective of the retailer is to maximize the long‐run average profit. Assuming zero lead time, we propose an efficient solution approach to the problem, which is also generalized to solve three extensions to the basic model. A feature of the present study is that we consider explicitly the influence of perishability on the demand. Among the insights gathered from the numerical analysis, we find that dynamic pricing aids extending shelf life and when disposal incurs a lower cost, or even a positive salvage value, the retailer is induced to dispose earlier since the benefit of selling new inventory offsets the los...
International Journal of Computer Applications in Technology, 2005
Given the imbalances of an international shipping company's empty containers in ports all over th... more Given the imbalances of an international shipping company's empty containers in ports all over the world, we study the problem of the dynamic distribution of empty containers with and without third party leasing from another company and develop a decision support system to solve the empty container distribution problem.
Scholars, practitioners, and students in operations research and management science (OR/MS) often... more Scholars, practitioners, and students in operations research and management science (OR/MS) often hesitate to use traditional approaches to evaluate journal quality because of the inconsistency of these approaches to perceptions and other associated biases. We introduce an alternative approach, which is based on Google's PageRank, to evaluate 31 OR/MS journals. This approach enhances the impact factor method by considering both citation quantity and quality. When we apply our method to OR/MS journals, the results match survey opinions and significantly outperform rankings based on impact factors. In addition, we provide an extensive discussion of other methods that have been used to assess journal quality. Compared to these methods, our method is better able to discern quality differences for journals that are perceived to be of relatively higher quality. Most importantly, we integrate our method into a Web-based journal-ranking system.
We extend the traveling salesman problem with pickup and delivery and LIFO loading (TSPPDL) by co... more We extend the traveling salesman problem with pickup and delivery and LIFO loading (TSPPDL) by considering two additional factors, namely the use of multiple vehicles and a limitation on the total distance that a vehicle can travel; both of these factors occur commonly in practice. We call the resultant problem the multiple pickup and delivery traveling salesman problem with LIFO loading and distance constraints (MTSPPD-LD). This paper presents a thorough preliminary investigation of the MTSPPD-LD. We propose six new neighborhood operators for the problem that can be used in search heuristics or meta-heuristics. We also devise a two-stage approach for solving the problem, where the first stage focuses on minimizing the number of vehicles required and the second stage minimizes the total travel distance. We consider two possible approaches for the first stage (simulated annealing and ejection pool) and two for the second stage (variable neighborhood search and probabilistic tabu search). Our computational results serve as benchmarks for future researchers on the problem.
Hospitals need to repeatedly produce duty rosters for its nursing staff. The good scheduling of n... more Hospitals need to repeatedly produce duty rosters for its nursing staff. The good scheduling of nurses has impact on the quality of health care, the recruitment of nurses, the development of budgets and other nursing functions. The nurse rostering problem (NRP) has been the subject of much study. This paper presents a brief overview, in the form of a bibliographic survey, of the many models and methodologies available to solve the NRP.
In the capacitated team orienteering problem (CTOP), we are given a set of homogeneous vehicles a... more In the capacitated team orienteering problem (CTOP), we are given a set of homogeneous vehicles and a set of customers each with a service demand value and a profit value. A vehicle can get the profit of a customer by satisfying its demand, but the total demand of all customers in its route cannot exceed the vehicle capacity and the length of the route must be within a specified maximum. The problem is to design a set of routes that maximizes the total profit collected by the vehicles. In this article, we propose a new heuristic algorithm for the CTOP using the ejection pool framework with an adaptive strategy and a diversification mechanism based on toggling between two priority rules. Experimental results show that our algorithm can match or improve all the best known results on the standard CTOP benchmark instances proposed by Archetti et al. (2008).
In this paper, we extend upon current research in the vehicle routing problem whereby labour regu... more In this paper, we extend upon current research in the vehicle routing problem whereby labour regulations affect planning horizons, and therefore, profitability. We call this extension the multiperiod vehicle routing problem with profit (mVRPP). The goal is to determine routes for a set of vehicles that maximizes profitability from visited locations, based on the conditions that vehicles can only travel during stipulated working hours within each period in a given planning horizon and that the vehicles are only required to return to the depot at the end of the last period. We propose an effective memetic algorithm with a gianttour representation to solve the mVRPP. To efficiently evaluate a chromosome, we develop a greedy procedure to partition a given giant-tour into individual routes, and prove that the resultant partition is optimal. We evaluate the effectiveness of our memetic algorithm with extensive experiments based on a set of modified benchmark instances. The results indicate that our approach generates high-quality solutions that are reasonably close to the best known solutions or proven optima, and significantly better than the solutions obtained using heuristics employed by professional schedulers.
Practise is one of the most important steps in learning the art of computer programming. Unfortun... more Practise is one of the most important steps in learning the art of computer programming. Unfortunately, human grading of programming assignments is a tedious and error-prone task, a problem compounded by the large enrolments of many programming courses. As a result, students in such courses tend to be given fewer programming assignments than should be ideally given. One solution to this problem is to automate the grading process such that students can electronically submit their programming assignments and receive instant feedback. This paper studies the implementation of one such automated grading system, called the Online Judge, in the School of Computing of the National University of Singapore for a compulsory first-year course that teaches basic programming techniques with over 700 students, describing the student reactions and behavior as well as the difficulties encountered. The Online Judge was also successfully employed for an advanced undergraduate course and an introductory high school course.
This report describes and evaluates the implementation and applicability of an automatic programm... more This report describes and evaluates the implementation and applicability of an automatic programming assignment grading system we named the online judge. We compared this with the manual grading system that is currently being used and showed that the automatic grading system, when implemented carefully, is more convenient, fairer, and more secure than the former. We have successfully tested the system on two courses. However, further studies need to be conducted to improve the effectiveness of learning through this system.
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Papers by Brenda Li