Pub Date : 2015-06-22DOI: 10.1080/0740817X.2015.1055389
Kan Wu, Ning Zhao
Tandem queues with a finite buffer capacity are the common structures embedded in practical production systems. We study the properties of tandem queues with a finite buffer capacity and non-overlapping service times subject to time-based preemptive breakdowns. Different from prior aggregation and decomposition approaches, we view a tandem queue as an integrated system and develop an innovative approach to analyze the performance of a dual tandem queue through the insight from Friedman's reduction method. We show that the system capacity of a dual tandem queue with a finite buffer and breakdowns can be less than its bottleneck-sees-initial-arrivals system due to the existence of virtual interruptions. Furthermore, the virtual interruptions depend on job arrival rates in general. Approximate models are derived using priority queues and the concept of virtual interruptions.
{"title":"Analysis of dual tandem queues with a finite buffer capacity and non-overlapping service times and subject to breakdowns","authors":"Kan Wu, Ning Zhao","doi":"10.1080/0740817X.2015.1055389","DOIUrl":"https://doi.org/10.1080/0740817X.2015.1055389","url":null,"abstract":"Tandem queues with a finite buffer capacity are the common structures embedded in practical production systems. We study the properties of tandem queues with a finite buffer capacity and non-overlapping service times subject to time-based preemptive breakdowns. Different from prior aggregation and decomposition approaches, we view a tandem queue as an integrated system and develop an innovative approach to analyze the performance of a dual tandem queue through the insight from Friedman's reduction method. We show that the system capacity of a dual tandem queue with a finite buffer and breakdowns can be less than its bottleneck-sees-initial-arrivals system due to the existence of virtual interruptions. Furthermore, the virtual interruptions depend on job arrival rates in general. Approximate models are derived using priority queues and the concept of virtual interruptions.","PeriodicalId":13379,"journal":{"name":"IIE Transactions","volume":"47 1","pages":"1329 - 1341"},"PeriodicalIF":0.0,"publicationDate":"2015-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/0740817X.2015.1055389","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59750705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-06-19DOI: 10.1080/0740817X.2015.1009759
Banafsheh Behzad, S. Jacobson, M. Robbins
The United States pediatric vaccine market is examined using Bertrand–Edgeworth–Chamberlin price competition. The proposed game captures interactions between symmetric, capacity-constrained manufacturers in a differentiated, single-product market with linear demand. Results indicate that a unique pure strategy equilibrium exists in the case where the capacities of the manufacturers are at their extreme. For the capacity region where no pure strategy equilibrium exists, there exists a mixed strategy equilibrium where the distribution function, its support, and the expected profit of the manufacturers are characterized. Three game instances are introduced to model the United States pediatric vaccine market. In each instance, the manufacturers are assumed to have equal capacity in producing vaccines. Vaccines are differentiated based upon the number of reported adverse medical events for that vaccine. Using a game-theoretic model, equilibrium prices are computed for each monovalent vaccine. Results indicate that the equilibrium prices for monovalent vaccines are lower than the federal contract prices. The numerical results provide both a lower and upper bound for the vaccine equilibrium prices in the public sector, based on the capacity of the vaccine manufacturers. Results illustrate the importance of several model parameters such as market demand and vaccine adverse events on the equilibrium prices. Supplementary materials are available for this article. Go to the publisher’s online edition of IIE Transactions for datasets, additional tables, detailed proofs, etc.
{"title":"A symmetric capacity-constrained differentiated oligopoly model for the United States pediatric vaccine market with linear demand","authors":"Banafsheh Behzad, S. Jacobson, M. Robbins","doi":"10.1080/0740817X.2015.1009759","DOIUrl":"https://doi.org/10.1080/0740817X.2015.1009759","url":null,"abstract":"The United States pediatric vaccine market is examined using Bertrand–Edgeworth–Chamberlin price competition. The proposed game captures interactions between symmetric, capacity-constrained manufacturers in a differentiated, single-product market with linear demand. Results indicate that a unique pure strategy equilibrium exists in the case where the capacities of the manufacturers are at their extreme. For the capacity region where no pure strategy equilibrium exists, there exists a mixed strategy equilibrium where the distribution function, its support, and the expected profit of the manufacturers are characterized. Three game instances are introduced to model the United States pediatric vaccine market. In each instance, the manufacturers are assumed to have equal capacity in producing vaccines. Vaccines are differentiated based upon the number of reported adverse medical events for that vaccine. Using a game-theoretic model, equilibrium prices are computed for each monovalent vaccine. Results indicate that the equilibrium prices for monovalent vaccines are lower than the federal contract prices. The numerical results provide both a lower and upper bound for the vaccine equilibrium prices in the public sector, based on the capacity of the vaccine manufacturers. Results illustrate the importance of several model parameters such as market demand and vaccine adverse events on the equilibrium prices. Supplementary materials are available for this article. Go to the publisher’s online edition of IIE Transactions for datasets, additional tables, detailed proofs, etc.","PeriodicalId":13379,"journal":{"name":"IIE Transactions","volume":"52 1","pages":"1252 - 1266"},"PeriodicalIF":0.0,"publicationDate":"2015-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/0740817X.2015.1009759","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59749116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-06-03DOI: 10.1080/0740817X.2014.953646
Andrew Romich, Guanghui Lan, J. C. Smith
This article examines the problem of placing stationary monitors in a continuous space, with the goal of minimizing an adversary’s maximum probability of traversing an origin–destination route without being detected. The problem arises, for instance, in defending against the transport of illicit material through some area of interest. In particular, we consider the deployment of monitors whose probability of detecting an intruder is a function of the distance between the monitor and the intruder. Under the assumption that the detection probabilities are mutually independent, a two-stage mixed-integer nonlinear programming formulation is constructed for the problem. An algorithm is provided that optimally locates monitors in a continuous space. Then, this problem is examined for the case where the monitor locations are restricted to two different discretized subsets of continuous space. The analysis provides optimization algorithms for each case and derives bounds on the worst-case optimality gap between the restrictions and the initial (continuous-space) problem. Empirically, it is shown that discretized solutions can be obtained whose worst-case and actual optimality gaps are well within practical limits.
{"title":"Algorithms for optimizing the placement of stationary monitors","authors":"Andrew Romich, Guanghui Lan, J. C. Smith","doi":"10.1080/0740817X.2014.953646","DOIUrl":"https://doi.org/10.1080/0740817X.2014.953646","url":null,"abstract":"This article examines the problem of placing stationary monitors in a continuous space, with the goal of minimizing an adversary’s maximum probability of traversing an origin–destination route without being detected. The problem arises, for instance, in defending against the transport of illicit material through some area of interest. In particular, we consider the deployment of monitors whose probability of detecting an intruder is a function of the distance between the monitor and the intruder. Under the assumption that the detection probabilities are mutually independent, a two-stage mixed-integer nonlinear programming formulation is constructed for the problem. An algorithm is provided that optimally locates monitors in a continuous space. Then, this problem is examined for the case where the monitor locations are restricted to two different discretized subsets of continuous space. The analysis provides optimization algorithms for each case and derives bounds on the worst-case optimality gap between the restrictions and the initial (continuous-space) problem. Empirically, it is shown that discretized solutions can be obtained whose worst-case and actual optimality gaps are well within practical limits.","PeriodicalId":13379,"journal":{"name":"IIE Transactions","volume":"47 1","pages":"556 - 576"},"PeriodicalIF":0.0,"publicationDate":"2015-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/0740817X.2014.953646","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59746479","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-06-03DOI: 10.1080/0740817X.2014.938845
L. Sherry
Environmental regulations require airports to report air quality emissions inventories (i.e., tons emitted) for aircraft emissions such as carbon oxides (COx) and nitrogen oxides (NOx). Traditional methods for emission inventory calculations yield over-estimated inventories due an assumption of the use of maximum takeoff thrust settings for all departures. To reduce costs, airlines use “reduced” thrust settings (such as derated or flex temperature thrust settings) that can be up to 25% lower than the maximum takeoff thrust setting. Thrust data for each flight operation are not readily available to those responsible for the emission inventory. This article describes an approach to estimate the actual takeoff thrust for each flight operation using algorithms that combine radar surveillance track data, weather data, and standardized aircraft performance models. A case study for flights from Chicago's O’Hare airport exhibited an average takeoff thrust of 86% of maximum takeoff thrust (within 4% of the average for actual takeoff thrust settings). The implications and limitations of this method are discussed.
{"title":"Improving the accuracy of airport emissions inventories using disparate datasets","authors":"L. Sherry","doi":"10.1080/0740817X.2014.938845","DOIUrl":"https://doi.org/10.1080/0740817X.2014.938845","url":null,"abstract":"Environmental regulations require airports to report air quality emissions inventories (i.e., tons emitted) for aircraft emissions such as carbon oxides (COx) and nitrogen oxides (NOx). Traditional methods for emission inventory calculations yield over-estimated inventories due an assumption of the use of maximum takeoff thrust settings for all departures. To reduce costs, airlines use “reduced” thrust settings (such as derated or flex temperature thrust settings) that can be up to 25% lower than the maximum takeoff thrust setting. Thrust data for each flight operation are not readily available to those responsible for the emission inventory. This article describes an approach to estimate the actual takeoff thrust for each flight operation using algorithms that combine radar surveillance track data, weather data, and standardized aircraft performance models. A case study for flights from Chicago's O’Hare airport exhibited an average takeoff thrust of 86% of maximum takeoff thrust (within 4% of the average for actual takeoff thrust settings). The implications and limitations of this method are discussed.","PeriodicalId":13379,"journal":{"name":"IIE Transactions","volume":"125 4 1","pages":"577 - 585"},"PeriodicalIF":0.0,"publicationDate":"2015-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/0740817X.2014.938845","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59745640","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-06-03DOI: 10.1080/0740817X.2014.937019
Kyung Sung Jung, H. N. Geismar, Michael Pinedo, C. Sriskandarajah
This article considers the problems of scheduling operations in single-gripper and dual-gripper bufferless robotic cells in which the arrangement of machines is circular. The cells are designed to produce identical parts under the free-pickup criterion with additive intermachine travel time. The objective is to find a cyclic sequence of robot moves that minimizes the long-run average time required to produce a part or, equivalently, that maximizes the throughput. Obtaining an efficient algorithm for an approximation to an optimal k-unit cyclic solution (over all k ≥ 1) is the focus of this article. The proposed algorithms introduce a new class of schedules, which are refered to as epi-cyclic cycles. A polynomial algorithm with a 5/3-approximation to an optimal k-unit cycle over all cells is developed. The performed structural analysis for dual-gripper cells leads to a polynomial-time algorithm that provides at worst a 3/2-approximation for the practically relevant case in which the dual-gripper switch time is less than twice the intermachine robot movement time. A computational study demonstrates that the algorithm performs much better on average than this worst-case bound suggests. The performed theoretical studies are a stepping stone for researching the complexity status of the corresponding domain. They also provide theoretical as well as practical insights that are useful in maximizing productivity of any cell configuration with either type of robot.
{"title":"Approximations to optimal sequences in single-gripper and dual-gripper robotic cells with circular layouts","authors":"Kyung Sung Jung, H. N. Geismar, Michael Pinedo, C. Sriskandarajah","doi":"10.1080/0740817X.2014.937019","DOIUrl":"https://doi.org/10.1080/0740817X.2014.937019","url":null,"abstract":"This article considers the problems of scheduling operations in single-gripper and dual-gripper bufferless robotic cells in which the arrangement of machines is circular. The cells are designed to produce identical parts under the free-pickup criterion with additive intermachine travel time. The objective is to find a cyclic sequence of robot moves that minimizes the long-run average time required to produce a part or, equivalently, that maximizes the throughput. Obtaining an efficient algorithm for an approximation to an optimal k-unit cyclic solution (over all k ≥ 1) is the focus of this article. The proposed algorithms introduce a new class of schedules, which are refered to as epi-cyclic cycles. A polynomial algorithm with a 5/3-approximation to an optimal k-unit cycle over all cells is developed. The performed structural analysis for dual-gripper cells leads to a polynomial-time algorithm that provides at worst a 3/2-approximation for the practically relevant case in which the dual-gripper switch time is less than twice the intermachine robot movement time. A computational study demonstrates that the algorithm performs much better on average than this worst-case bound suggests. The performed theoretical studies are a stepping stone for researching the complexity status of the corresponding domain. They also provide theoretical as well as practical insights that are useful in maximizing productivity of any cell configuration with either type of robot.","PeriodicalId":13379,"journal":{"name":"IIE Transactions","volume":"47 1","pages":"634 - 652"},"PeriodicalIF":0.0,"publicationDate":"2015-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/0740817X.2014.937019","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59745669","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-06-03DOI: 10.1080/0740817X.2014.938844
M. E. Nikoofal, M. Gümüş
The ability to understand and predict the sequence of events leading to a terrorist attack is one of the main issues in developing pre-emptive defense strategies for homeland security. This article, explores the value of terrorist’s private information on a government’s defense allocation decision. In particular, two settings with different informational structures are considered. In the first setting, the government knows the terrorist’s target preference but does not know whether the terrorist is fully rational in his target selection decision. In the second setting, the government knows the degree of rationality of the terrorist but does not know the terrorist’s target preference. The government’s equilibrium budget allocation strategy for each setting is fully characterized and it is shown that the government makes resource allocation decisions by comparing her valuation for each target with a set of thresholds. The Value Of Information (VOI) from the perspective of the government for each setting is derived. The obtained results show that VOI mainly depends on the government’s budget and the degree of heterogeneity among the targets. In general, VOI goes to zero when the government’s budget is high enough. However, the impact of heterogeneity among the targets on VOI further depends on whether the terrorist’s target preference matches those of the government’s or not. Finally, various extensions on the baseline model are performed and it is shown that the structural properties of budget allocation equilibrium still hold true.
{"title":"On the value of terrorist’s private information in a government’s defensive resource allocation problem","authors":"M. E. Nikoofal, M. Gümüş","doi":"10.1080/0740817X.2014.938844","DOIUrl":"https://doi.org/10.1080/0740817X.2014.938844","url":null,"abstract":"The ability to understand and predict the sequence of events leading to a terrorist attack is one of the main issues in developing pre-emptive defense strategies for homeland security. This article, explores the value of terrorist’s private information on a government’s defense allocation decision. In particular, two settings with different informational structures are considered. In the first setting, the government knows the terrorist’s target preference but does not know whether the terrorist is fully rational in his target selection decision. In the second setting, the government knows the degree of rationality of the terrorist but does not know the terrorist’s target preference. The government’s equilibrium budget allocation strategy for each setting is fully characterized and it is shown that the government makes resource allocation decisions by comparing her valuation for each target with a set of thresholds. The Value Of Information (VOI) from the perspective of the government for each setting is derived. The obtained results show that VOI mainly depends on the government’s budget and the degree of heterogeneity among the targets. In general, VOI goes to zero when the government’s budget is high enough. However, the impact of heterogeneity among the targets on VOI further depends on whether the terrorist’s target preference matches those of the government’s or not. Finally, various extensions on the baseline model are performed and it is shown that the structural properties of budget allocation equilibrium still hold true.","PeriodicalId":13379,"journal":{"name":"IIE Transactions","volume":"47 1","pages":"533 - 555"},"PeriodicalIF":0.0,"publicationDate":"2015-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/0740817X.2014.938844","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59745777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-05-15DOI: 10.1080/0740817X.2015.1047068
Yingchieh Yeh, B. Schmeiser
We propose VAMP1RE, a single criterion for rating and ranking confidence-interval procedures (CIPs) that use a fixed sample size. The quality of a CIP is traditionally thought to be many dimensional, typically composed of the probability of covering the unknown performance measure and the mean (and sometimes the standard deviation) of interval width, each of these over some set of nominal coverage probabilities. These many criteria reflect symptoms, rather than causes, of CIP quality. The VAMP1RE criterion focuses on two causes: departure from validity—violation of assumptions—and inability to mimic—the dissimilarity, for every data set, of a CIP’s interval to that of an ideal CIP. The ideal CIP is both valid (that is, adheres to all assumptions) and is an agreed-upon standard; possibly the ideal CIP is allowed knowledge not available to the real-world CIPs of interest. A high inability to mimic the ideal CIP implies that a CIP uses data inefficiently. For a given CIP, the VAMP1RE criterion is the expected squared difference between Schruben’s coverage values (analogous to p values) arising from the given CIP and from the ideal CIP. The implication is that an interval arising from a particular data set is good not because it is large or small but, rather, it is good to the extent that it is similar to the interval provided by the ideal CIP. We discuss the relationship to Schruben’s coverage function, provide a graphical interpretation, decompose the VAMP1RE criterion into the two cause components, and provide examples to illustrate that the VAMP1RE criterion provides numerical values that are useful for rating and ranking CIPs.
{"title":"VAMP1RE: a single criterion for rating and ranking confidence-interval procedures","authors":"Yingchieh Yeh, B. Schmeiser","doi":"10.1080/0740817X.2015.1047068","DOIUrl":"https://doi.org/10.1080/0740817X.2015.1047068","url":null,"abstract":"We propose VAMP1RE, a single criterion for rating and ranking confidence-interval procedures (CIPs) that use a fixed sample size. The quality of a CIP is traditionally thought to be many dimensional, typically composed of the probability of covering the unknown performance measure and the mean (and sometimes the standard deviation) of interval width, each of these over some set of nominal coverage probabilities. These many criteria reflect symptoms, rather than causes, of CIP quality. The VAMP1RE criterion focuses on two causes: departure from validity—violation of assumptions—and inability to mimic—the dissimilarity, for every data set, of a CIP’s interval to that of an ideal CIP. The ideal CIP is both valid (that is, adheres to all assumptions) and is an agreed-upon standard; possibly the ideal CIP is allowed knowledge not available to the real-world CIPs of interest. A high inability to mimic the ideal CIP implies that a CIP uses data inefficiently. For a given CIP, the VAMP1RE criterion is the expected squared difference between Schruben’s coverage values (analogous to p values) arising from the given CIP and from the ideal CIP. The implication is that an interval arising from a particular data set is good not because it is large or small but, rather, it is good to the extent that it is similar to the interval provided by the ideal CIP. We discuss the relationship to Schruben’s coverage function, provide a graphical interpretation, decompose the VAMP1RE criterion into the two cause components, and provide examples to illustrate that the VAMP1RE criterion provides numerical values that are useful for rating and ranking CIPs.","PeriodicalId":13379,"journal":{"name":"IIE Transactions","volume":"47 1","pages":"1203 - 1216"},"PeriodicalIF":0.0,"publicationDate":"2015-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/0740817X.2015.1047068","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59750211","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-05-13DOI: 10.1080/0740817X.2014.999900
Zheng Zhang, Xiaolan Xie
This study is devoted to the appointment scheduling (AS) for a sequence of surgeries with random durations served by multiple operating rooms (Multi-OR). Surgeries are assigned to ORs dynamically on a first-come, first-serve (FCFS) basis. It materially differs from past literature in the sense that dynamic assignments are proactively anticipated in the determination of appointment times. A discrete-event framework is proposed to model the execution of the surgery schedule and to evaluate the sample path gradient of a total cost incurred by surgeon waiting, OR idling, and OR overtime. The sample path cost function is shown to be unimodal, Lipchitz-continuous, and differentiable w.p.1 and the expected cost function continuously differentiable. A stochastic approximation algorithm based on unbiased gradient estimators is proposed and extensive numerical experiments suggest that it converges to a global optimum. A series of numerical experiments is performed to show the significant benefits of the Multi-OR setting and properties of the optimal solution with respect to various system parameters such as cost structure and numbers of surgeries and ORs.
{"title":"Simulation-based optimization for surgery appointment scheduling of multiple operating rooms","authors":"Zheng Zhang, Xiaolan Xie","doi":"10.1080/0740817X.2014.999900","DOIUrl":"https://doi.org/10.1080/0740817X.2014.999900","url":null,"abstract":"This study is devoted to the appointment scheduling (AS) for a sequence of surgeries with random durations served by multiple operating rooms (Multi-OR). Surgeries are assigned to ORs dynamically on a first-come, first-serve (FCFS) basis. It materially differs from past literature in the sense that dynamic assignments are proactively anticipated in the determination of appointment times. A discrete-event framework is proposed to model the execution of the surgery schedule and to evaluate the sample path gradient of a total cost incurred by surgeon waiting, OR idling, and OR overtime. The sample path cost function is shown to be unimodal, Lipchitz-continuous, and differentiable w.p.1 and the expected cost function continuously differentiable. A stochastic approximation algorithm based on unbiased gradient estimators is proposed and extensive numerical experiments suggest that it converges to a global optimum. A series of numerical experiments is performed to show the significant benefits of the Multi-OR setting and properties of the optimal solution with respect to various system parameters such as cost structure and numbers of surgeries and ORs.","PeriodicalId":13379,"journal":{"name":"IIE Transactions","volume":"67 1","pages":"1012 - 998"},"PeriodicalIF":0.0,"publicationDate":"2015-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/0740817X.2014.999900","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59748875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-04-28DOI: 10.1080/0740817X.2015.1033038
Y. Duanmu, Qiang Huang
Selective Area Metal-Organic Chemical Vapor Deposition (SA-MOCVD) is a promising technique for the scale-up of nanowire fabrication. Our previous study investigated the growth mechanism of SA-MOCVD processes by quantifying contributions from various diffusion sources. However, the edge effect on nanostructure uniformity captured by skirt area diffusion was not quantitatively analyzed. This work further improves our understanding of the process by considering the edge effect as a superposition of skirt area diffusion and “blocking effect” and optimizing the edge effect for uniformity control of nanowire growth. We directly model the blocking effect of nanowires in the process of precursor diffusion from the skirt area to the center of a substrate. The improved model closely captures the distribution of the nanowire length across the substrate. Physical interpretation of the edge effect is provided. With the established model, we provide a method to optimize the width of the skirt area to improve the predicted structural uniformity of SA-MOCVD growth.
{"title":"Analysis and optimization of the edge effect for III–V nanowire synthesis via selective area metal-organic chemical vapor deposition","authors":"Y. Duanmu, Qiang Huang","doi":"10.1080/0740817X.2015.1033038","DOIUrl":"https://doi.org/10.1080/0740817X.2015.1033038","url":null,"abstract":"Selective Area Metal-Organic Chemical Vapor Deposition (SA-MOCVD) is a promising technique for the scale-up of nanowire fabrication. Our previous study investigated the growth mechanism of SA-MOCVD processes by quantifying contributions from various diffusion sources. However, the edge effect on nanostructure uniformity captured by skirt area diffusion was not quantitatively analyzed. This work further improves our understanding of the process by considering the edge effect as a superposition of skirt area diffusion and “blocking effect” and optimizing the edge effect for uniformity control of nanowire growth. We directly model the blocking effect of nanowires in the process of precursor diffusion from the skirt area to the center of a substrate. The improved model closely captures the distribution of the nanowire length across the substrate. Physical interpretation of the edge effect is provided. With the established model, we provide a method to optimize the width of the skirt area to improve the predicted structural uniformity of SA-MOCVD growth.","PeriodicalId":13379,"journal":{"name":"IIE Transactions","volume":"47 1","pages":"1424 - 1431"},"PeriodicalIF":0.0,"publicationDate":"2015-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/0740817X.2015.1033038","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59750382","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-04-28DOI: 10.1080/0740817X.2015.1034897
J. Brimberg, Z. Drezner
We consider a continuous location problem for p concentric circles serving a given set of demand points. Each demand point is serviced by the closest circle. The objective is to minimize the sum of weighted distances between demand points and their closest circle. We analyze and solve the problem when demand is uniformly and continuously distributed in a disk and when a finite number of demand points are located in the plane. Heuristic and exact algorithms are proposed for the solution of the discrete demand problem. A much faster heuristic version of the exact algorithm is also proposed and tested. The exact algorithm solves the largest tested problem with 1000 demand points in about 3.5 hours. The faster heuristic version solves it in about 2 minutes.
{"title":"A location–allocation problem with concentric circles","authors":"J. Brimberg, Z. Drezner","doi":"10.1080/0740817X.2015.1034897","DOIUrl":"https://doi.org/10.1080/0740817X.2015.1034897","url":null,"abstract":"We consider a continuous location problem for p concentric circles serving a given set of demand points. Each demand point is serviced by the closest circle. The objective is to minimize the sum of weighted distances between demand points and their closest circle. We analyze and solve the problem when demand is uniformly and continuously distributed in a disk and when a finite number of demand points are located in the plane. Heuristic and exact algorithms are proposed for the solution of the discrete demand problem. A much faster heuristic version of the exact algorithm is also proposed and tested. The exact algorithm solves the largest tested problem with 1000 demand points in about 3.5 hours. The faster heuristic version solves it in about 2 minutes.","PeriodicalId":13379,"journal":{"name":"IIE Transactions","volume":"47 1","pages":"1397 - 1406"},"PeriodicalIF":0.0,"publicationDate":"2015-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/0740817X.2015.1034897","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59750017","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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