Bryan Norman - Academia.edu (original) (raw)
Papers by Bryan Norman
…, Jan 1, 2012
Abstract Abu Dhabi Health Services (SEHA) has established Disease Prevention and Screening Center... more Abstract Abu Dhabi Health Services (SEHA) has established Disease Prevention and Screening Centers (DPSCs) to provide health screening for third-country national (TCN) workers. In anticipation of increases in the number of TCN workers who will require health screening, SEHA is building new centers to accommodate the increased requirements. As part of the design process, we used queuing and simulation models to model (1) the current DPSC configuration,(2) a configuration based on individual lanes, and (3) a configuration ...
The unequal area facility design problem has been studied in the literature generally by consider... more The unequal area facility design problem has been studied in the literature generally by considering block layout separate from detailed design. This paper shows a tractable method for concurrently optimizing department shape and location within the facility, and selection of the appropriate number of input/output (I/O) stations per department and then optimally locating them. The distance metric used is the
Annals of Operations Research, 2004
Job rotation is a useful tool that can be used in many work settings to produce task variety for ... more Job rotation is a useful tool that can be used in many work settings to produce task variety for workers and to reduce worker fatigue and injuries. Developing a job rotation plan requires determining the set of jobs to be included in the rotation, the rotation sequence, and the proper length of the rotation interval. Previous research has considered both
New techniques from computational intelligence have attracted the interest of manufacturing resea... more New techniques from computational intelligence have attracted the interest of manufacturing researchers in academia, government and industry. These techniques include artificial neural networks, tabu search and evolutionary computing. While these computational techniques inspired by nature have shown promise in many manufacturing applications such as robotics, machine vision, process control, process planning and scheduling, there is little in the literature on their practical use. Moving these techniques from simulated data sets, toy problems or laboratory settings to real industrial applications is a large and uncertain step. This paper focuses on the technology transfer issues and solutions when using computational intelligence for off-line control of manufacturing processes and scheduling of production environments.
In this chapter we have presented three greedy heuristics for mapping applications onto a reconfi... more In this chapter we have presented three greedy heuristics for mapping applications onto a reconfigurable device oriented for low-energy execution. The three heuristics are a deterministic top-down greedy algorithm described in Section 4, a greedy algorithm with randomization discussed in Section 5 based on the deterministic algorithm flow, and a partial MILP greedy heuristic presented in Section 6. Here we compare the deterministic, randomized, weighted randomized, and sliding partial MILP heuristics described in Section 4, Section 5.1, Section 5.2, and Section 6, respectively. The comparisons are made using a 5:1-based interconnect and are shown in Table 11. The results compare the different heuristics in terms of fabric size, path length increase, and mapping time.
Vaccine, 2015
Many of the world&amp... more Many of the world's vaccine supply chains do not adequately provide vaccines, prompting several questions: how are vaccine supply chains currently structured, are these structures closely tailored to individual countries, and should these supply chains be radically redesigned? We segmented the 57 GAVI-eligible countries' vaccine supply chains based on their structure/morphology, analyzed whether these segments correlated with differences in country characteristics, and then utilized HERMES to develop a detailed simulation model of three sample countries' supply chains and explore the cost and impact of various alternative structures. The majority of supply chains (34 of 57) consist of four levels, despite serving a wide diversity of geographical areas and population sizes. These four-level supply chains loosely fall into three clusters [(1) 18 countries relatively more bottom-heavy, i.e., many more storage locations lower in the supply chain, (2) seven with relatively more storage locations in both top and lower levels, and (3) nine comparatively more top-heavy] which do not correlate closely with any of the country characteristics considered. For all three cluster types, our HERMES modeling found that simplified systems (a central location shipping directly to immunization locations with a limited number of Hubs in between) resulted in lower operating costs. A standard four-tier design template may have been followed for most countries and raises the possibility that simpler and more tailored designs may be warranted.
International Journal of Production Research, 2002
ABSTRACT
Background: In Niger and other African countries, both rotavirus and pneumococcal disease cause h... more Background: In Niger and other African countries, both rotavirus and pneumococcal disease cause high morbidity and mortality. Over 65% of deaths associated with rotavirus infection occurred in eleven Asian and African countries in 2004. Of these countries, Niger had the highest under-five mortality rate (392 per 100,000 population <5 years). Objectives: Although there is great potential for the rotavirus vaccine (RV) and the seven-valent pneumococcal conjugate vaccine (PCV-7) to fill significant needs in West Africa, it is unclear whether the supply chains (i.e., the series of steps required to get a vaccine from the manufacturers to the arms and mouths of patients) of countries such as Niger can handle introductions of such vaccines. Methods: We developed mathematical models of the entire Niger vaccine supply chain to determine the impact of introducing the rotavirus vaccine (RV), the pneumococcal vaccine (PCV-7) or both, to the Niger expanded programs on immunization (EPI). Res...
Vaccine, 2015
Within a typical vaccine supply chain, vaccines are packaged into individual cylindrical vials (e... more Within a typical vaccine supply chain, vaccines are packaged into individual cylindrical vials (each containing one or more doses) that are bundled together in rectangular &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;inner packs&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; for transport via even larger groupings such as cold boxes and vaccine carriers. The variability of vaccine inner pack and vial size may hinder efficient vaccine distribution because it constrains packing of cold boxes and vaccine carriers to quantities that are often inappropriate or suboptimal in the context of country-specific vaccination guidelines. We developed in Microsoft Excel (Microsoft Corp., Redmond, WA) a spreadsheet model that evaluated the impact of different packing schemes for the Benin routine regimen plus the introduction of the Rotarix vaccine. Specifically, we used the model to compare the current packing scheme to that of a proposed modular packing scheme. Conventional packing of a Dometic RCW25 that aims to maximize fully-immunized children (FICs) results in 123 FICs and a packing efficiency of 81.93% compared to a maximum of 155 FICs and 94.1% efficiency for an alternative modular packaging system. Our analysis suggests that modular packaging systems could offer significant advantages over conventional vaccine packaging systems with respect to space efficiency and potential FICs, when they are stored in standard vaccine carrying devices. This allows for more vaccines to be stored within the same volume while also simplifying the procedures used by field workers to pack storage devices. Ultimately, modular packaging systems could be a simple way to help increase vaccine coverage worldwide.
Vaccine, 2015
While new mechanisms such as advance market commitments and co-financing policies of the GAVI All... more While new mechanisms such as advance market commitments and co-financing policies of the GAVI Alliance are allowing low-and middle-income countries to gain access to vaccines faster than ever, understanding the full scope of vaccine program costs is essential to ensure adequate resource mobilization. This costing analysis examines the vaccine costs, supply chain costs, and service delivery costs of immunization programs for routine immunization and for supplemental immunization activities (SIAs) for vaccines related to 18 antigens in 94 countries across the decade, 2011-2020. Vaccine costs were calculated using GAVI price forecasts for GAVI-eligible countries, and assumptions from the PAHO Revolving Fund and UNICEF for middle-income countries not supported by the GAVI Alliance. Vaccine introductions and coverage levels were projected primarily based on GAVI's Adjusted Demand Forecast. Supply chain costs including costs of transportation, storage, and labor were estimated by developing a mechanistic model using data generated by the HERMES discrete event simulation models. Service delivery costs were abstracted from comprehensive multi-year plans for the majority of GAVI-eligible countries and regression analysis was conducted to extrapolate costs to additional countries.
Engineering Management Journal, 2002
ABSTRACT This article describes an approach and methodology that explicitly considers the assessm... more ABSTRACT This article describes an approach and methodology that explicitly considers the assessment of human capital in a lean manufacturing environment supported by cellular manufacturing. It details a systematic approach where human capital is inventoried in the form of developing a skills database. Specific critical skills are identified, grouped, and placed onto a Skills Inventory Form (SIF). The SIF is used to assess the skill levels of each worker via an employee, supervisor, and consensus assessment approach. The approach is illustrated in a Fortune 100 company, showing how to use it to drive training requirements, change hiring practices, assign workers, and establish compensation and reward systems.
Proceedings of 1997 IEEE International Conference on Evolutionary Computation (ICEC '97), 1997
We introduce a unique scheduling and tool assignment problem that arises for multiple spindle mac... more We introduce a unique scheduling and tool assignment problem that arises for multiple spindle machine tools. The capability of these machines to perform simultaneous operations on one or more parts creates constraints that are not found in the traditional scheduling literature. Two solution methodologies using a genetic algorithm with the random keys encoding are introduced for these problems. One is
Lecture Notes in Computer Science, 2000
The design of survivable mesh based STM networks has received considerable attention in recent ye... more The design of survivable mesh based STM networks has received considerable attention in recent years and is a complex multiconstraint optimization problem. In this paper, a new spare capacity planning methodology is proposed utilizing genetic algorithms. The method is based on forcing flows/traffic which are on paths that are disjoint to share backup spare capacity. The major advantages of the new approach are a polynomial time complexity and the capability of incorporating nonlinear variables such as nonlinear cost functions into the solution algorithm. Numerical results illustrating the form of the genetic algorithm solution and comparing the proposed methodology to existing techniques from the literature are presented.
Computers & Industrial Engineering, 2014
ABSTRACT The objective of Design for Supply Chain (DFSC) is to design a supply chain in parallel ... more ABSTRACT The objective of Design for Supply Chain (DFSC) is to design a supply chain in parallel to designing a new product. Risk is an inherent element of this process. Although supply chain risk models and product development risk models are available, there are few models that consider the combined effect of risk to product development and the supply chain. This gap is filled by the development of a DFSC and risk model that looks at design, supply chain and risk concurrently. The model consists of two components. First, a Mixed Integer Programming (MIP) model makes the DFSC decisions while simultaneously considering time-to-market risk, supplier reliability risk and strategic exposure risk. The results from the MIP are then used in the second model component which is a discrete event simulation. The simulation tests the robustness of the MIP solution for supplier capacity risk and demand risk. When a decision maker is potentially facing either of these risks the simulation shows whether it is best to use an alternative solution or proceed with the MIP solution. The model provides analytical results, but also allows decision makers to use their own judgment to select the best option for overall profitability. In conclusion, testing shows that risk mitigation strategies can and should be determined from the DFSC and risk model, but that they will be dependent on the specific design problem being solved.
This paper presents a formulation of the facilities block layout problem which explicitly conside... more This paper presents a formulation of the facilities block layout problem which explicitly considers uncertainty in material handling costs on a continuous scale by use of expected values and standard deviations of product forecasts. This formulation is solved using a genetic algorithm meta-heuristic with a flexible bay construct of the departments and total facility area. It is shown that depending on the attitude of the decision-maker towards uncertainty, the optimal design can change significantly. Furthermore, designs can be optimized directly for robustness over a range of uncertainty that is pre-specified by the user. This formulation offers a computationally tractable and intuitively appealing alternative to previous stochastic layout formulations that are based on discrete scenario probabilities.
This paper considers the problem of determining the locations of wind generators in a wind farm c... more This paper considers the problem of determining the locations of wind generators in a wind farm consisting of many generators. The objective is to find a generator placement that maximizes profit, which is the product of the cost efficiency of the generators and the total power output from the wind farm. Generator placement is significant because if generator A is located close to generator B and is located downwind of generator B then the power output of generator A is reduced by an amount that varies with the distance between the generators. The problem can be formulated using mathematical programming but to solve the problem one cannot employ traditional optimization methods. Therefore, a greedy improvement heuristic methodology is developed and described in detail. The effectiveness of the proposed heuristic is demonstrated on a suite of test problems. These results indicate that the proposed method represents an effective solution strategy for this problem.
This paper presents a mixed-integer programming formulation to find optimal solutions for the blo... more This paper presents a mixed-integer programming formulation to find optimal solutions for the block layout problem with unequal departmental areas arranged in flexible bays. The nonlinear department area constraints are modeled in a continuous plane without using any surrogate constraints. The formulation is extensively tested on problems from the literature. © 2005 Elsevier B.V. All rights reserved.
International Journal of Modelling and Simulation, 2012
Vaccine, Jan 7, 2014
New vaccine introductions have put strains on vaccine supply chains around the world. While incre... more New vaccine introductions have put strains on vaccine supply chains around the world. While increasing storage and transportation may be the most straightforward options, it is also important to consider what financial and operational benefits can be incurred. In 2012, suboptimal vaccine coverage and impending vaccine introductions prompted the Republic of Benin's Ministry of Health (MOH) to explore ways to improve their vaccine supply chain. Working alongside the Beninese MOH, we utilized our computational model, HERMES, to explore the impact on cost and vaccine availability of three possible options: (1) consolidating the Commune level to a Health Zone level, (2) removing the Commune level completely, and (3) removing the Commune level and expanding to 12 Department Stores. We also analyzed the impact of adding shipping loops during delivery. At baseline, new vaccine introductions without any changes to the current system increased the logistics cost per dose ($0.23 to $0.26) ...
…, Jan 1, 2012
Abstract Abu Dhabi Health Services (SEHA) has established Disease Prevention and Screening Center... more Abstract Abu Dhabi Health Services (SEHA) has established Disease Prevention and Screening Centers (DPSCs) to provide health screening for third-country national (TCN) workers. In anticipation of increases in the number of TCN workers who will require health screening, SEHA is building new centers to accommodate the increased requirements. As part of the design process, we used queuing and simulation models to model (1) the current DPSC configuration,(2) a configuration based on individual lanes, and (3) a configuration ...
The unequal area facility design problem has been studied in the literature generally by consider... more The unequal area facility design problem has been studied in the literature generally by considering block layout separate from detailed design. This paper shows a tractable method for concurrently optimizing department shape and location within the facility, and selection of the appropriate number of input/output (I/O) stations per department and then optimally locating them. The distance metric used is the
Annals of Operations Research, 2004
Job rotation is a useful tool that can be used in many work settings to produce task variety for ... more Job rotation is a useful tool that can be used in many work settings to produce task variety for workers and to reduce worker fatigue and injuries. Developing a job rotation plan requires determining the set of jobs to be included in the rotation, the rotation sequence, and the proper length of the rotation interval. Previous research has considered both
New techniques from computational intelligence have attracted the interest of manufacturing resea... more New techniques from computational intelligence have attracted the interest of manufacturing researchers in academia, government and industry. These techniques include artificial neural networks, tabu search and evolutionary computing. While these computational techniques inspired by nature have shown promise in many manufacturing applications such as robotics, machine vision, process control, process planning and scheduling, there is little in the literature on their practical use. Moving these techniques from simulated data sets, toy problems or laboratory settings to real industrial applications is a large and uncertain step. This paper focuses on the technology transfer issues and solutions when using computational intelligence for off-line control of manufacturing processes and scheduling of production environments.
In this chapter we have presented three greedy heuristics for mapping applications onto a reconfi... more In this chapter we have presented three greedy heuristics for mapping applications onto a reconfigurable device oriented for low-energy execution. The three heuristics are a deterministic top-down greedy algorithm described in Section 4, a greedy algorithm with randomization discussed in Section 5 based on the deterministic algorithm flow, and a partial MILP greedy heuristic presented in Section 6. Here we compare the deterministic, randomized, weighted randomized, and sliding partial MILP heuristics described in Section 4, Section 5.1, Section 5.2, and Section 6, respectively. The comparisons are made using a 5:1-based interconnect and are shown in Table 11. The results compare the different heuristics in terms of fabric size, path length increase, and mapping time.
Vaccine, 2015
Many of the world&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp... more Many of the world&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s vaccine supply chains do not adequately provide vaccines, prompting several questions: how are vaccine supply chains currently structured, are these structures closely tailored to individual countries, and should these supply chains be radically redesigned? We segmented the 57 GAVI-eligible countries&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; vaccine supply chains based on their structure/morphology, analyzed whether these segments correlated with differences in country characteristics, and then utilized HERMES to develop a detailed simulation model of three sample countries&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; supply chains and explore the cost and impact of various alternative structures. The majority of supply chains (34 of 57) consist of four levels, despite serving a wide diversity of geographical areas and population sizes. These four-level supply chains loosely fall into three clusters [(1) 18 countries relatively more bottom-heavy, i.e., many more storage locations lower in the supply chain, (2) seven with relatively more storage locations in both top and lower levels, and (3) nine comparatively more top-heavy] which do not correlate closely with any of the country characteristics considered. For all three cluster types, our HERMES modeling found that simplified systems (a central location shipping directly to immunization locations with a limited number of Hubs in between) resulted in lower operating costs. A standard four-tier design template may have been followed for most countries and raises the possibility that simpler and more tailored designs may be warranted.
International Journal of Production Research, 2002
ABSTRACT
Background: In Niger and other African countries, both rotavirus and pneumococcal disease cause h... more Background: In Niger and other African countries, both rotavirus and pneumococcal disease cause high morbidity and mortality. Over 65% of deaths associated with rotavirus infection occurred in eleven Asian and African countries in 2004. Of these countries, Niger had the highest under-five mortality rate (392 per 100,000 population <5 years). Objectives: Although there is great potential for the rotavirus vaccine (RV) and the seven-valent pneumococcal conjugate vaccine (PCV-7) to fill significant needs in West Africa, it is unclear whether the supply chains (i.e., the series of steps required to get a vaccine from the manufacturers to the arms and mouths of patients) of countries such as Niger can handle introductions of such vaccines. Methods: We developed mathematical models of the entire Niger vaccine supply chain to determine the impact of introducing the rotavirus vaccine (RV), the pneumococcal vaccine (PCV-7) or both, to the Niger expanded programs on immunization (EPI). Res...
Vaccine, 2015
Within a typical vaccine supply chain, vaccines are packaged into individual cylindrical vials (e... more Within a typical vaccine supply chain, vaccines are packaged into individual cylindrical vials (each containing one or more doses) that are bundled together in rectangular &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;inner packs&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; for transport via even larger groupings such as cold boxes and vaccine carriers. The variability of vaccine inner pack and vial size may hinder efficient vaccine distribution because it constrains packing of cold boxes and vaccine carriers to quantities that are often inappropriate or suboptimal in the context of country-specific vaccination guidelines. We developed in Microsoft Excel (Microsoft Corp., Redmond, WA) a spreadsheet model that evaluated the impact of different packing schemes for the Benin routine regimen plus the introduction of the Rotarix vaccine. Specifically, we used the model to compare the current packing scheme to that of a proposed modular packing scheme. Conventional packing of a Dometic RCW25 that aims to maximize fully-immunized children (FICs) results in 123 FICs and a packing efficiency of 81.93% compared to a maximum of 155 FICs and 94.1% efficiency for an alternative modular packaging system. Our analysis suggests that modular packaging systems could offer significant advantages over conventional vaccine packaging systems with respect to space efficiency and potential FICs, when they are stored in standard vaccine carrying devices. This allows for more vaccines to be stored within the same volume while also simplifying the procedures used by field workers to pack storage devices. Ultimately, modular packaging systems could be a simple way to help increase vaccine coverage worldwide.
Vaccine, 2015
While new mechanisms such as advance market commitments and co-financing policies of the GAVI All... more While new mechanisms such as advance market commitments and co-financing policies of the GAVI Alliance are allowing low-and middle-income countries to gain access to vaccines faster than ever, understanding the full scope of vaccine program costs is essential to ensure adequate resource mobilization. This costing analysis examines the vaccine costs, supply chain costs, and service delivery costs of immunization programs for routine immunization and for supplemental immunization activities (SIAs) for vaccines related to 18 antigens in 94 countries across the decade, 2011-2020. Vaccine costs were calculated using GAVI price forecasts for GAVI-eligible countries, and assumptions from the PAHO Revolving Fund and UNICEF for middle-income countries not supported by the GAVI Alliance. Vaccine introductions and coverage levels were projected primarily based on GAVI's Adjusted Demand Forecast. Supply chain costs including costs of transportation, storage, and labor were estimated by developing a mechanistic model using data generated by the HERMES discrete event simulation models. Service delivery costs were abstracted from comprehensive multi-year plans for the majority of GAVI-eligible countries and regression analysis was conducted to extrapolate costs to additional countries.
Engineering Management Journal, 2002
ABSTRACT This article describes an approach and methodology that explicitly considers the assessm... more ABSTRACT This article describes an approach and methodology that explicitly considers the assessment of human capital in a lean manufacturing environment supported by cellular manufacturing. It details a systematic approach where human capital is inventoried in the form of developing a skills database. Specific critical skills are identified, grouped, and placed onto a Skills Inventory Form (SIF). The SIF is used to assess the skill levels of each worker via an employee, supervisor, and consensus assessment approach. The approach is illustrated in a Fortune 100 company, showing how to use it to drive training requirements, change hiring practices, assign workers, and establish compensation and reward systems.
Proceedings of 1997 IEEE International Conference on Evolutionary Computation (ICEC '97), 1997
We introduce a unique scheduling and tool assignment problem that arises for multiple spindle mac... more We introduce a unique scheduling and tool assignment problem that arises for multiple spindle machine tools. The capability of these machines to perform simultaneous operations on one or more parts creates constraints that are not found in the traditional scheduling literature. Two solution methodologies using a genetic algorithm with the random keys encoding are introduced for these problems. One is
Lecture Notes in Computer Science, 2000
The design of survivable mesh based STM networks has received considerable attention in recent ye... more The design of survivable mesh based STM networks has received considerable attention in recent years and is a complex multiconstraint optimization problem. In this paper, a new spare capacity planning methodology is proposed utilizing genetic algorithms. The method is based on forcing flows/traffic which are on paths that are disjoint to share backup spare capacity. The major advantages of the new approach are a polynomial time complexity and the capability of incorporating nonlinear variables such as nonlinear cost functions into the solution algorithm. Numerical results illustrating the form of the genetic algorithm solution and comparing the proposed methodology to existing techniques from the literature are presented.
Computers & Industrial Engineering, 2014
ABSTRACT The objective of Design for Supply Chain (DFSC) is to design a supply chain in parallel ... more ABSTRACT The objective of Design for Supply Chain (DFSC) is to design a supply chain in parallel to designing a new product. Risk is an inherent element of this process. Although supply chain risk models and product development risk models are available, there are few models that consider the combined effect of risk to product development and the supply chain. This gap is filled by the development of a DFSC and risk model that looks at design, supply chain and risk concurrently. The model consists of two components. First, a Mixed Integer Programming (MIP) model makes the DFSC decisions while simultaneously considering time-to-market risk, supplier reliability risk and strategic exposure risk. The results from the MIP are then used in the second model component which is a discrete event simulation. The simulation tests the robustness of the MIP solution for supplier capacity risk and demand risk. When a decision maker is potentially facing either of these risks the simulation shows whether it is best to use an alternative solution or proceed with the MIP solution. The model provides analytical results, but also allows decision makers to use their own judgment to select the best option for overall profitability. In conclusion, testing shows that risk mitigation strategies can and should be determined from the DFSC and risk model, but that they will be dependent on the specific design problem being solved.
This paper presents a formulation of the facilities block layout problem which explicitly conside... more This paper presents a formulation of the facilities block layout problem which explicitly considers uncertainty in material handling costs on a continuous scale by use of expected values and standard deviations of product forecasts. This formulation is solved using a genetic algorithm meta-heuristic with a flexible bay construct of the departments and total facility area. It is shown that depending on the attitude of the decision-maker towards uncertainty, the optimal design can change significantly. Furthermore, designs can be optimized directly for robustness over a range of uncertainty that is pre-specified by the user. This formulation offers a computationally tractable and intuitively appealing alternative to previous stochastic layout formulations that are based on discrete scenario probabilities.
This paper considers the problem of determining the locations of wind generators in a wind farm c... more This paper considers the problem of determining the locations of wind generators in a wind farm consisting of many generators. The objective is to find a generator placement that maximizes profit, which is the product of the cost efficiency of the generators and the total power output from the wind farm. Generator placement is significant because if generator A is located close to generator B and is located downwind of generator B then the power output of generator A is reduced by an amount that varies with the distance between the generators. The problem can be formulated using mathematical programming but to solve the problem one cannot employ traditional optimization methods. Therefore, a greedy improvement heuristic methodology is developed and described in detail. The effectiveness of the proposed heuristic is demonstrated on a suite of test problems. These results indicate that the proposed method represents an effective solution strategy for this problem.
This paper presents a mixed-integer programming formulation to find optimal solutions for the blo... more This paper presents a mixed-integer programming formulation to find optimal solutions for the block layout problem with unequal departmental areas arranged in flexible bays. The nonlinear department area constraints are modeled in a continuous plane without using any surrogate constraints. The formulation is extensively tested on problems from the literature. © 2005 Elsevier B.V. All rights reserved.
International Journal of Modelling and Simulation, 2012
Vaccine, Jan 7, 2014
New vaccine introductions have put strains on vaccine supply chains around the world. While incre... more New vaccine introductions have put strains on vaccine supply chains around the world. While increasing storage and transportation may be the most straightforward options, it is also important to consider what financial and operational benefits can be incurred. In 2012, suboptimal vaccine coverage and impending vaccine introductions prompted the Republic of Benin's Ministry of Health (MOH) to explore ways to improve their vaccine supply chain. Working alongside the Beninese MOH, we utilized our computational model, HERMES, to explore the impact on cost and vaccine availability of three possible options: (1) consolidating the Commune level to a Health Zone level, (2) removing the Commune level completely, and (3) removing the Commune level and expanding to 12 Department Stores. We also analyzed the impact of adding shipping loops during delivery. At baseline, new vaccine introductions without any changes to the current system increased the logistics cost per dose ($0.23 to $0.26) ...