@article{fathi_fathi_2023, title={Bi-criteria set covering problem with conflict constraints}, volume={186}, ISSN={["1879-0550"]}, DOI={10.1016/j.cie.2023.109759}, abstractNote={In this article, we consider the set covering problem with conflict constraints, i.e., from each conflicting pair of columns, at most one column can appear in the feasible solution, and we seek to identify (select) a subset of columns so as to achieve two distinct objectives. The first objective is to maximize the number of rows covered by the selected subset of columns, and the second objective is to minimize the number of selected columns. In this context, we present a bi-criteria integer programming (IP) model and two corresponding epsilon-constraint methods to find the non-dominated frontier for this bi-criteria optimization problem. We then propose several families of valid inequalities for the corresponding IP models. Finally, through computational experiments, we demonstrate the effectiveness of the proposed methods.}, journal={COMPUTERS & INDUSTRIAL ENGINEERING}, author={Fathi, Saeed Saffari and Fathi, Yahya}, year={2023}, month={Dec} }
 @article{saffari_fathi_2022, title={Set covering problem with conflict constraints}, volume={143}, ISSN={["1873-765X"]}, DOI={10.1016/j.cor.2022.105763}, abstractNote={In this article, we consider the set covering problem with conflict constraints, i.e., from each conflicting pair of columns at most one column can appear in the feasible solution. For this problem, we propose appropriate pre-processing techniques and several families of Valid Inequalities (VIs) for the corresponding integer programming model that result from the simultaneous presence of the set covering constraints and the stable set (conflict) constraints. We then carry out a computational experiment to demonstrate the effectiveness of the proposed methods.}, journal={COMPUTERS & OPERATIONS RESEARCH}, author={Saffari, Saeed and Fathi, Yahya}, year={2022}, month={Jul} }
 @article{tutunchi_fathi_2020, title={Representative subsets of non-dominated points in the bi-criteria p-median p-dispersion problem}, volume={146}, ISSN={["1879-0550"]}, DOI={10.1016/j.cie.2020.106400}, abstractNote={One way to reduce the computational burden of solving a bi-criteria optimization problem would be to obtain only a subset of its non-dominated points (NDPs) as representative for the entire collection. We introduce a new criterion (index) to evaluate the effectiveness of a representative subset of non-dominated points in the context of the Bi-criteria p-Median p-Dispersion problem (BpMD). A key difference between our proposed index and those previously introduced in the open literature is that in those indexes the distance between an arbitrary NDP and its nearest NDP in the representative subset is determined along the direction of both objective functions, while in our proposed index this distance is determined only along the objective function for which the representing NDP is worst than the represented NDP. Along this direction, the proposed index provides an upper bound on the relative gap between the representing NDP and any NDP that it represents. We then employ this index to design an algorithm to find a representative subset of NDPs for the problem BpMD and demonstrate its effectiveness through a computational experiment. Although we develop this index in the context of the problem BpMD, it is potentially applicable in the context of other bi-criteria optimization problems as well.}, journal={COMPUTERS & INDUSTRIAL ENGINEERING}, author={Tutunchi, Golbarg Kazemi and Fathi, Yahya}, year={2020}, month={Aug} }
 @article{tutunchi_fathi_2019, title={Effective methods for solving the Bi-criteria p-Center and p-Dispersion problem}, volume={101}, ISSN={["1873-765X"]}, DOI={10.1016/j.cor.2018.08.009}, abstractNote={Given a collection of n locations and a symmetric measure of distance (difference) between each pair of locations, we seek to identify (select) a subset of p locations so as to achieve two distinct objectives. The first objective is to minimize the maximum dissimilarity (i.e., distance) between the selected locations and other locations. The second objective is to maximize the minimum distance (diversity) among the selected locations themselves. Based on the relationship between the max-min diversity problem and the node packing problem, we propose an integer programming (IP) model and a corresponding incremental algorithm to find the non-dominated frontier for this bi-criteria optimization problem. Subsequently we use the relationship between this IP model and a corresponding set-covering problem to propose effective methods for solving the former. Finally we employ the relationship between the node packing constraints and the set covering constraints to propose a new family of valid inequalities for the corresponding IP models that are potentially effective when solving large instances of these models. Through computational experiments we demonstrate the effectiveness of our proposed methods for solving relatively large instances of this bi-criteria optimization problem.}, journal={COMPUTERS & OPERATIONS RESEARCH}, author={Tutunchi, Golbarg Kazemi and Fathi, Yahya}, year={2019}, month={Jan}, pages={43–54} }
 @article{gopalswamy_fathi_uzsoy_2019, title={Valid inequalities for concave piecewise linear regression}, volume={47}, ISSN={["1872-7468"]}, DOI={10.1016/j.orl.2018.12.004}, abstractNote={We consider the problem of fitting a concave piecewise linear function to multivariate data using the Least Absolute Deviation objective. We propose new valid inequalities for the problem using the properties of concave functions. Results with univariate data show that the proposed valid inequalities improve the root relaxation lower bound, permitting significant improvements in solution time.}, number={1}, journal={OPERATIONS RESEARCH LETTERS}, author={Gopalswamy, Karthick and Fathi, Yahya and Uzsoy, Reha}, year={2019}, month={Jan}, pages={52–58} }
 @article{sayyady_fathi_2016, title={An integer programming approach for solving the p-dispersion problem}, volume={253}, ISSN={["1872-6860"]}, DOI={10.1016/j.ejor.2016.02.026}, abstractNote={Given a collection of n items (elements) and an associated symmetric distance dij between each pair of items i and j, we seek a subset P of these items (with a given cardinality p) so that the minimum pairwise distance among the selected items is maximized. This problem is known as the max–min diversity problem or the p-dispersion problem, and it is shown to be np-hard. We define a collection of node packing problems associated with each instance of this problem and employ a binary search among these node packing problems to devise an effective procedure for solving the original problem. We employ existing integer programming techniques, i.e., branch-and-bound and strong valid inequalities, to solve these node packing problems. Through a computational experiment we show that this approach can be used to solve relatively large instances of the p-dispersion problem, i.e., instances with more than 1000 items. We also discuss an application of this problem in the context of locating traffic sensors in a highway network.}, number={1}, journal={EUROPEAN JOURNAL OF OPERATIONAL RESEARCH}, author={Sayyady, Fatemeh and Fathi, Yahya}, year={2016}, month={Aug}, pages={216–225} }
 @inbook{alborzi_chirkova_doyle_fathi_2015, title={Determining Query Readiness for Structured Data}, volume={9263}, ISBN={9783319227283 9783319227290}, ISSN={0302-9743 1611-3349}, url={http://dx.doi.org/10.1007/978-3-319-22729-0_1}, DOI={10.1007/978-3-319-22729-0_1}, abstractNote={The outcomes and quality of organizational decisions depend on the characteristics of the data available for making the decisions and on the value of the data in the decision-making process. Toward enabling management of these aspects of data in analytics, we introduce and investigate Data Readiness Level (DRL), a quantitative measure of the value of a piece of data at a given point in a processing flow. Our DRL proposal is a multidimensional measure that takes into account the relevance, completeness, and utility of data with respect to a given analysis task. This study provides a formalization of DRL in a structured-data scenario, and illustrates how knowledge of rules and facts, both within and outside the given data, can be used to identify those transformations of the data that improve its DRL.}, booktitle={Big Data Analytics and Knowledge Discovery}, publisher={Springer International Publishing}, author={Alborzi, Farid and Chirkova, Rada and Doyle, Jon and Fathi, Yahya}, year={2015}, pages={3–14} }
 @inproceedings{alborzi_chirkova_doyle_fathi_2015, title={Determining query readiness for structured data}, volume={9263}, booktitle={Big data analytics and knowledge discovery}, author={Alborzi, F. and Chirkova, R. and Doyle, J. and Fathi, Y.}, year={2015}, pages={3–14} }
 @article{sayyady_tutunchi_fathi_2015, title={p-Median and p-dispersion problems: A bi-criteria analysis}, volume={61}, ISSN={["1873-765X"]}, DOI={10.1016/j.cor.2015.02.007}, abstractNote={Given a collection of n locations and a symmetric measure of distance (difference) between each pair of locations, we seek to identify (select) a subset of p locations so as to achieve two distinct objectives. The first objective is to use the selected locations as centers (medians) of p groups that would partition the entire collection and minimize the total distance between the locations and their respective group medians. The second objective is to maximize the minimum distance (diversity) among the selected locations themselves. We study this problem as a multi-objective optimization problem and propose an iterative algorithm to obtain its non-dominated frontier. At each iteration we construct and solve a 0–1 integer programming problem. Through a computational experiment we show that this algorithm is computationally effective for small to medium size instances of the problem. We also propose a Lagrangian heuristic algorithm for solving larger instances of this problem.}, journal={COMPUTERS & OPERATIONS RESEARCH}, author={Sayyady, Fatemeh and Tutunchi, Golbarg K. and Fathi, Yahya}, year={2015}, month={Sep}, pages={46–55} }
 @article{chaleshtarti_shadrokh_fathi_2014, title={Branch and Bound Algorithms for Resource Constrained Project Scheduling Problem Subject to Nonrenewable Resources with Prescheduled Procurement}, volume={2014}, ISSN={["1563-5147"]}, DOI={10.1155/2014/634649}, abstractNote={A lot of projects in real life are subject to some kinds of nonrenewable resources that are not exactly similar to the type defined in the project scheduling literature. The difference stems from the fact that, in those projects, contrary to the common assumption in the project scheduling literature, nonrenewable resources are not available in full amount at the beginning of the project, but they are procured along the project horizon. In this paper, we study this different type of nonrenewable resources. To that end, we extend the resource constrained project scheduling problem (RCPSP) by this resource type (RCPSP-NR) and customize four basic branch and bound algorithms of RCPSP for it, including precedence tree, extension alternatives, minimal delaying alternatives, and minimal forbidden sets. Several bounding and fathoming rules are introduced to the algorithms to shorten the enumeration process. We perform comprehensive experimental analysis using the four customized algorithms and also CPLEX solver.}, journal={MATHEMATICAL PROBLEMS IN ENGINEERING}, author={Chaleshtarti, A. Shirzadeh and Shadrokh, S. and Fathi, Y.}, year={2014} }
 @article{sayyady_fathi_list_stone_2013, title={Locating Traffic Sensors on a Highway Network Models and Algorithms}, ISSN={["2169-4052"]}, DOI={10.3141/2339-04}, abstractNote={ This paper considers the problem of finding optimal sensor locations on a traffic network with the goal of characterizing system use overall. The problem is studied for two practical scenarios. In the first scenario, it is assumed that there is a given number of sensors (p) to be located on the highway network. In this context, the problem is to find a collection of p locations among a given collection of candidate locations. In the second scenario, it is assumed that there is a cost (ci) associated with installing a sensor at each candidate location i and a total budget b. In this context, the problem is to find a collection of locations that provide the best possible characterization given the budget constraint. A metric is proposed for evaluating a potential solution, and then appropriate mathematical models are proposed for solving the problem for each scenario. It is shown that the budget-constrained problem is an extension of the well-known p-median problem. A new Lagrangian heuristic algorithm is presented for solving large instances of this problem when a budget constraint is imposed. A comprehensive computational experiment is used to demonstrate that the Lagrangian heuristic algorithm provides solutions for large-scale networks within reasonable execution times. Examples are based on locating weigh-in-motion sensors on a large-scale highway network. }, number={2339}, journal={TRANSPORTATION RESEARCH RECORD}, author={Sayyady, Fatemeh and Fathi, Yahya and List, George F. and Stone, John R.}, year={2013}, pages={30–38} }
 @inproceedings{huang_chirkova_fathi_2013, title={Two-stage stochastic view selection for data-analysis queries}, volume={186}, booktitle={Advances in databases and information systems}, author={Huang, R. and Chirkova, R. and Fathi, Y.}, year={2013}, pages={115–123} }
 @article{akhavan-tabatabaei_fathi_shanthikumar_2012, title={A Markov Chain Framework for Cycle Time Approximation of Toolsets}, volume={25}, ISSN={["1558-2345"]}, DOI={10.1109/tsm.2012.2202252}, abstractNote={Cycle time is a key performance measure in semiconductor manufacturing. Currently, discrete event simulation and queueing theory are the most common approaches to estimating the cycle time of a fabrication facility. However, the performance of both approaches has been unsatisfactory due to many factors, including the inability to perform in an environment where informal and unwritten operational rules exist. Such rules create dependence between the arrival and service processes of a toolset, and, hence, render the classical queueing models inaccurate. We propose a Markov chain framework that attempts to approximate the cycle time of a toolset in the presence of informal operational rules, and we compare our approach with classical queueing models through a series of numerical examples.}, number={4}, journal={IEEE TRANSACTIONS ON SEMICONDUCTOR MANUFACTURING}, author={Akhavan-Tabatabaei, Raha and Fathi, Yahya and Shanthikumar, J. George}, year={2012}, month={Nov}, pages={589–597} }
 @article{asgharzadeh talebi_chirkova_fathi_2013, title={An integer programming approach for the view and index selection problem}, volume={83}, ISSN={0169-023X}, url={http://dx.doi.org/10.1016/j.datak.2012.11.001}, DOI={10.1016/j.datak.2012.11.001}, abstractNote={The view- and index-selection problem is a combinatorial optimization problem that arises in the context of on-line analytical processing (OLAP) in database-management systems. We propose an integer programming (IP) model for this problem and study the properties of the views and indexes that appear in the optimal solution for this model. We then use these properties to remove a number of variables and constraints from the corresponding IP model and obtain a model that is significantly smaller, yet its optimal solution is guaranteed to be optimal for the original problem. This allows us to solve realistic-size instances of the problem in reasonable time using commercial IP solvers. Subsequently, we propose heuristic strategies to further reduce the size of this IP model and dramatically reduce its execution time, although we no longer guarantee that the reduced IP model offers a globally optimal solution for the original problem. Finally, we carry out an extensive computational study to evaluate the effectiveness of these IP models for solving the OLAP view- and index-selection problem.}, journal={Data & Knowledge Engineering}, publisher={Elsevier BV}, author={Asgharzadeh Talebi, Zohreh and Chirkova, Rada and Fathi, Yahya}, year={2013}, month={Jan}, pages={111–125} }
 @inbook{huang_chirkova_fathi_2012, title={Deterministic View Selection for Data-Analysis Queries: Properties and Algorithms}, ISBN={9783642330735 9783642330742}, ISSN={0302-9743 1611-3349}, url={http://dx.doi.org/10.1007/978-3-642-33074-2_15}, DOI={10.1007/978-3-642-33074-2_15}, abstractNote={The view-selection problem is a combinatorial optimization problem that arises in the context of on-line analytical processing (OLAP) in database management systems. We pose the problem as an integer programming (IP) model, study its structural properties, and propose effective techniques for reducing the search space of views and thus the size of the corresponding IP model. We then use these results to design both exact methods and heuristic algorithms that are effective for solving relatively large realistic-size instances of the problem.}, booktitle={Advances in Databases and Information Systems}, publisher={Springer Berlin Heidelberg}, author={Huang, Rong and Chirkova, Rada and Fathi, Yahya}, year={2012}, pages={195–208} }
 @inbook{huang_chirkova_fathi_2013, title={Two-Stage Stochastic View Selection for Data-Analysis Queries}, ISBN={9783642327407 9783642327414}, ISSN={2194-5357 2194-5365}, url={http://dx.doi.org/10.1007/978-3-642-32741-4_11}, DOI={10.1007/978-3-642-32741-4_11}, abstractNote={We consider the problem of selecting an optimal set of views to answer a given collection of queries at the present time (stage 1) as well as several collections of queries in the future (stage 2), with a given probability of occurrence associated with each collection, so as to minimize the expected value of the corresponding query response time, while keeping the total size of the views within a given limit. We formulate this problem as a two-stage stochastic programming problem. We show that this model is equivalent to an integer programming (IP) model that can be solved via various commercial IP solvers. We also study the relationship between the queries and the views in this context and use this relationship to reduce the size of the corresponding IP model, hence increase the scalability of our proposed approach.}, booktitle={Advances in Intelligent Systems and Computing}, publisher={Springer Berlin Heidelberg}, author={Huang, Rong and Chirkova, Rada and Fathi, Yahya}, year={2013}, pages={115–123} }
 @article{fathi_kianfar_2012, title={An efficient model for the crosscut optimisation problem in a wood processing mill}, volume={50}, ISSN={["0020-7543"]}, DOI={10.1080/00207543.2010.538446}, abstractNote={We propose a dynamic programming model for the crosscut optimisation problem. This problem arises in the context of cutting lumber (rip-first) in order to obtain cubic blocks (cut-pieces) with required dimensions and surface characteristics. We propose a novel approach for matching the pattern of defects on all four surfaces of an incoming strip of wood with the surface requirements of the cut-pieces as specified in a given cut-bill, and determine an effective cutting pattern for each incoming strip accordingly. Our proposed dynamic programming model results in fast execution times as shown by the results of a computational experiment. The model is deployed in a software package that has been implemented successfully in several major rough mills.}, number={2}, journal={INTERNATIONAL JOURNAL OF PRODUCTION RESEARCH}, author={Fathi, Yahya and Kianfar, Kiavash}, year={2012}, pages={485–497} }
 @article{liu_fathi_2012, title={The nearest point problem in a polyhedral set and its extensions}, volume={53}, ISSN={["1573-2894"]}, DOI={10.1007/s10589-011-9448-5}, number={1}, journal={COMPUTATIONAL OPTIMIZATION AND APPLICATIONS}, author={Liu, Zhe and Fathi, Yahya}, year={2012}, month={Sep}, pages={115–130} }
 @article{allen_fathi_gross_mace_2010, title={An optimal and near-optimal strategy to selecting individuals for transfer in captive breeding programs}, volume={143}, ISSN={["1873-2917"]}, DOI={10.1016/j.biocon.2010.08.003}, abstractNote={As species extinction rates continue to rise, zoos have adopted a more active role in the conservation of endangered species. A central concern is to preserve genetic diversity of zoological populations. Accordingly, when selecting individuals to transfer to new or existing populations, zoo managers must consider the genetic effects on all populations involved. We propose a quadratic integer programming (IP) model to identify a group of individuals to transfer that maximizes genetic diversity within two subpopulations. We then reduce this model to a linear IP formulation and apply it to the California condor (Gymnogyps californianus) studbook. After simplifying the linear IP model, optimality is achieved within a reasonable time limit when a limited number of individuals are relocated. We also develop a local improvement algorithm (LIA) to efficiently provide near-optimal solutions when we increase the number of transferred individuals. The LIA quickly obtains optimal solutions when few individuals are transferred and in most cases, the LIA outperforms MetaMK, an existing program used to select animals for transfer.}, number={11}, journal={BIOLOGICAL CONSERVATION}, author={Allen, S. D. and Fathi, Y. and Gross, K. and Mace, M.}, year={2010}, month={Nov}, pages={2858–2863} }
 @article{kianfar_fathi_2010, title={Generating facets for finite master cyclic group polyhedra using n-step mixed integer rounding functions}, volume={207}, ISSN={["0377-2217"]}, DOI={10.1016/j.ejor.2010.04.021}, abstractNote={The n-step mixed integer rounding (MIR) functions generate n-step MIR inequalities for MIP problems and are facets for the infinite group problems. We show that the n-step MIR functions also directly generate facets for the finite master cyclic group polyhedra especially in many cases where the breakpoints of the n-step MIR function are not necessarily at the elements of the group (hence the linear interpolation of the facet coefficients obtained has more than two slopes).}, number={1}, journal={EUROPEAN JOURNAL OF OPERATIONAL RESEARCH}, author={Kianfar, Kiavash and Fathi, Yahya}, year={2010}, month={Nov}, pages={105–109} }
 @article{kefeli_uzsoy_fathi_kay_2011, title={Using a mathematical programming model to examine the marginal price of capacitated resources}, volume={131}, ISSN={["1873-7579"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79952613605&partnerID=MN8TOARS}, DOI={10.1016/j.ijpe.2010.03.018}, abstractNote={Accurate information on dual prices of capacitated resources is of interest in a number of applications, such as cost allocation and pricing. To gain insight we focus on the dual prices of capacity and demand in a single-stage single-product production-inventory system, and discuss their interpretation. In particular, we examine the behavior of two different production planning models: a conventional linear programming model and a nonlinear model that captures queuing behavior at resources in an aggregate manner using nonlinear clearing functions. The classical linear programming formulation consistently underestimates the dual price of capacity due to its failure to capture the effects of queuing. The clearing function formulation, in contrast, produces positive dual prices even when utilization is below one and exhibits more realistic behavior, such as holding finished inventory at utilization levels below one.}, number={1}, journal={INTERNATIONAL JOURNAL OF PRODUCTION ECONOMICS}, author={Kefeli, Ali and Uzsoy, Reha and Fathi, Yahya and Kay, Michael}, year={2011}, month={May}, pages={383–391} }
 @article{liu_fathi_2011, title={An active index algorithm for the nearest point problem in a polyhedral cone}, volume={49}, ISSN={["0926-6003"]}, DOI={10.1007/s10589-009-9303-0}, number={3}, journal={COMPUTATIONAL OPTIMIZATION AND APPLICATIONS}, author={Liu, Zhe and Fathi, Yahya}, year={2011}, month={Jul}, pages={435–456} }
 @inbook{kormilitsin_chirkova_fathi_stallmann_2009, title={Systematic Exploration of Efficient Query Plans for Automated Database Restructuring}, ISBN={9783642039720 9783642039737}, ISSN={0302-9743 1611-3349}, url={http://dx.doi.org/10.1007/978-3-642-03973-7_11}, DOI={10.1007/978-3-642-03973-7_11}, abstractNote={We consider the problem of selecting views and indexes that minimize the evaluation costs of the important queries under an upper bound on the disk space available for storing the views/indexes selected to be materialized. We propose a novel end-to-end approach that focuses on systematic exploration of plans for evaluating the queries. Specifically, we propose a framework (architecture) and algorithms that enable selection of views/indexes that contribute to the most efficient plans for the input queries, subject to the space bound. We present strong optimality guarantees on our architecture. Our algorithms search for sets of competitive plans for queries expressed in the language of conjunctive queries with arithmetic comparisons. This language captures the full expressive power of SQL select-project-join queries, which are common in practical database systems. Our experimental results demonstrate the competitiveness and scalability of our approach.}, booktitle={Advances in Databases and Information Systems}, publisher={Springer Berlin Heidelberg}, author={Kormilitsin, Maxim and Chirkova, Rada and Fathi, Yahya and Stallmann, Matthias}, year={2009}, pages={133–148} }
 @article{kianfar_fathi_2009, title={Generalized mixed integer rounding inequalities: facets for infinite group polyhedra}, volume={120}, ISSN={["0025-5610"]}, DOI={10.1007/s10107-008-0216-y}, number={2}, journal={MATHEMATICAL PROGRAMMING}, author={Kianfar, Kiavash and Fathi, Yahya}, year={2009}, month={Sep}, pages={313–346} }
 @article{kulkarni_fathi_2007, title={A very large scale neighborhood search algorithm for the q-mode problem}, volume={39}, ISSN={["0740-817X"]}, DOI={10.1080/07408170701416657}, abstractNote={The q-mode problem is a combinatorial optimization problem that arises in the context of partitioning a given collection of data vectors with categorical attributes. A neighborhood search algorithm is proposed for solving the q-mode problem. This algorithm is based on a very large scale neighborhood that is implicitly searched using network flow techniques. The algorithm is evaluated through a computational experiment using randomly generated instances. The results show that in general this algorithm obtains very-good-quality local optima, and that in instances with strong natural clusters the algorithm consistently finds optimal or near-optimal solutions.}, number={10}, journal={IIE TRANSACTIONS}, author={Kulkarni, Girish and Fathi, Yahya}, year={2007}, month={Oct}, pages={971–984} }
 @article{morgan_fathi_2008, title={Algorithms for the q-model clustering problem with application in switching cabinet manufacturing}, volume={189}, ISSN={["1872-6860"]}, DOI={10.1016/j.ejor.2007.02.060}, abstractNote={The model configuration problem (MCP) is a combinatorial optimization problem with application in the telecommunications manufacturing industry. The product is a switching cabinet, defined by a number of positions (slots) in which specific circuit packs are installed according to the customer requirements (configurations). Variety of customer requirements leads to a relatively large number of distinct configurations. In order to streamline the manufacturing process, a large number of switching cabinets with identical configurations (model cabinets) are produced in advance. A customer order is then filled by selecting a model cabinet whose configuration is relatively close to the customer configuration and performing any necessary circuit pack exchanges to make its configuration identical to the customer requirement. The manufacturing costs are proportional to the number of these circuit pack exchanges, and the q-model configuration problem is to design q different model configurations so as to minimize the total number of exchanges for a given collection of customer orders. We propose three heuristic algorithms for solving the q-model configuration problem and carry out a computational experiment to evaluate their effectiveness.}, number={3}, journal={EUROPEAN JOURNAL OF OPERATIONAL RESEARCH}, author={Morgan, Shona D. and Fathi, Yahya}, year={2008}, month={Sep}, pages={939–951} }
 @article{kulkarni_fathi_2007, title={Integer programming models for the q-mode problem}, volume={182}, ISSN={["1872-6860"]}, DOI={10.1016/j.ejor.2006.08.039}, abstractNote={The q-mode problem is a combinatorial optimization problem that requires partitioning of objects into clusters. We discuss theoretical properties of an existing mixed integer programming (MIP) model for this problem and offer alternative models and enhancements. Through a comprehensive experiment we investigate computational properties of these MIP models. This experiment reveals that, in practice, the MIP approach is more effective for instances containing strong natural clusters and it is not as effective for instances containing weak natural clusters. The experiment also reveals that one of the MIP models that we propose is more effective than the other models for solving larger instances of the problem.}, number={2}, journal={EUROPEAN JOURNAL OF OPERATIONAL RESEARCH}, author={Kulkarni, Girish and Fathi, Yahya}, year={2007}, month={Oct}, pages={612–625} }
 @inbook{li_talebi_chirkova_fathi_2005, title={A Formal Model for the Problem of View Selection for Aggregate Queries}, ISBN={9783540285854 9783540318958}, ISSN={0302-9743 1611-3349}, url={http://dx.doi.org/10.1007/11547686_10}, DOI={10.1007/11547686_10}, abstractNote={We present a formal analysis of the following view-selection problem: Given a set of queries and a database, return definitions of views that, when materialized in the database, would reduce the evaluation costs of the queries. Optimizing the layout of stored data using view selection has a direct impact on the performance of the entire database system. At the same time, the optimization problem is intractable, even under natural restrictions on the types of queries of interest. In this paper we use an integer-programming model to obtain optimal solutions to the problem of view selection for aggregate queries on data warehouses. We also report the results of the post-optimality analysis that we performed to determine/observe the impact of changing certain input characteristics on the optimal solution.}, booktitle={Advances in Databases and Information Systems}, publisher={Springer Berlin Heidelberg}, author={Li, Jingni and Talebi, Zohreh Asgharzadeh and Chirkova, Rada and Fathi, Yahya}, year={2005}, pages={125–138} }
 @article{morgan_fathi_taheri_2004, title={Algorithms for the model configuration problem}, volume={36}, ISSN={["1545-8830"]}, DOI={10.1080/07408170490245469}, abstractNote={The model configuration problem is a combinatorial optimization problem that arises in the context of switching cabinet manufacturing in the telecommunication industry. We discuss the manufacturing environment and define the q-model problem in this context, for q ≥ 1. We then discuss the structural properties of the q-model problem, and propose an efficient procedure for solving the 1-model problem. We also propose several heuristic procedures for solving the 2-model problem, and present an evaluation of these procedures through an extensive computational experiment.}, number={2}, journal={IIE TRANSACTIONS}, author={Morgan, SD and Fathi, Y and Taheri, J}, year={2004}, month={Feb}, pages={169–180} }
 @article{wardono_fathi_2004, title={A tabu search algorithm for the multi-stage parallel machine problem with limited buffer capacities}, volume={155}, ISSN={["1872-6860"]}, DOI={10.1016/S0377-2217(02)00873-1}, abstractNote={We investigate the problem of scheduling N jobs on parallel machines in L successive stages with limited buffer capacities between stages. The primary objective is to find a schedule that would minimize the makespan. This problem is shown to be NP-hard in the strong sense. We develop a tabu search algorithm for this problem in which the search is limited to the space of permutation vectors of size N. This vector represents the order in which the given set of jobs are performed in the first stage, and we propose a procedure to construct a complete schedule associated with every permutation vector. We conduct an extensive computational experiment using randomly generated instances with different structures and different buffer capacities. We also solve several specific instances of the problem from the open literature. All empirical evidence suggest that the proposed algorithm is an effective method for solving this problem.}, number={2}, journal={EUROPEAN JOURNAL OF OPERATIONAL RESEARCH}, author={Wardono, B and Fathi, Y}, year={2004}, month={Jun}, pages={380–401} }
 @article{fathi_aksakalli_2004, title={Heuristic methods for gang-rip saw arbor design}, volume={154}, ISSN={["0377-2217"]}, DOI={10.1016/S0377-2217(02)00796-8}, abstractNote={Abstract We consider the problem of design and scheduling of arbors for a computer assisted gang-rip saw system. Such systems are typically used within the furniture manufacturing industry for processing lumber. We discuss the computational complexity of the problem, and develop several heuristic procedures for solving it. These procedures are based on the principles of local improvement, simulated annealing, and genetic algorithms. The results of a computational experiment are also presented.}, number={3}, journal={EUROPEAN JOURNAL OF OPERATIONAL RESEARCH}, author={Fathi, Y and Aksakalli, V}, year={2004}, month={May}, pages={626–640} }
 @article{koksal_fathi_2003, title={Statistical tolerancing using designed experiments in a noisy environment}, volume={44}, ISSN={["0360-8352"]}, DOI={10.1016/S0360-8352(02)00234-6}, abstractNote={We consider the method of designed experiments for statistical tolerance analysis, and study the impact of experimental error on its results. It is observed that presence of random error in the experiment environment (e.g. laboratory) could introduce bias in the moment estimators and increases their respective variances. We propose adjustments to the method that would reduce the bias as well as the variance of these estimators. A numerical example is presented.}, number={3}, journal={COMPUTERS & INDUSTRIAL ENGINEERING}, author={Koksal, G and Fathi, Y}, year={2003}, month={Mar}, pages={515–526} }
 @article{fathi_barnette_2002, title={Heuristic procedures for the parallel machine problem with tool switches}, volume={40}, ISSN={["0020-7543"]}, DOI={10.1080/00207540110076115}, abstractNote={We address the problem of scheduling a set of parts with given processing times and tool requirements on m identical parallel machines. The problem is to find an allocation of the machines to the parts, a proper sequence for the parts assigned to each machine, and a corresponding tool-switching plan for each machine so as to minimize the makespan. It is demonstrated that this problem is np-hard , and three heuristic procedures are proposed for solving it. The first procedure is a multi-start local improvement procedure, and various neighborhood structures and search strategies are discussed in this context. The second procedure is a variation of the list-processing routine that is commonly used for the parallel machine problem. Finally, the last procedure is an adaptation of a well-known constructive procedure for the k -travelling salesman problem. Results of a limited computational experiment are also presented in which the makespan obtained via each heuristic procedure is compared with a proposed lower bound and with other reference values.}, number={1}, journal={INTERNATIONAL JOURNAL OF PRODUCTION RESEARCH}, author={Fathi, Y and Barnette, KW}, year={2002}, month={Jan}, pages={151–164} }
 @article{fathi_palko_2001, title={A mathematical model and a heuristic procedure for the robust design problem with high-low tolerances}, volume={33}, DOI={10.1080/07408170108936901}, abstractNote={We introduce the concept of robust design in the context of high-low tolerancing and propose a mathematical programming model for it. In situations where the transfer function is available either in closed form or through computer simulation, this model can be solved using conventional non-linear programming techniques. We also introduce an approximation procedure for solving this problem experimentally. This procedure can be used in situations where either the transfer function is not available in closed form or the variables are discrete or categorical. A numerical example and two case studies from the open literature are solved using these techniques and results are presented.}, number={12}, journal={IIE Transactions}, author={Fathi, Yahya and Palko, D.}, year={2001}, pages={1121–1127} }
 @article{eldessouki_fathi_rouphail_2001, title={Meta-optimization using cellular automata with application to the combined trip distribution and assignment system optimal problem}, volume={16}, ISSN={["1093-9687"]}, DOI={10.1111/0885-9507.00241}, abstractNote={In this paper, meta‐optimization and cellular automata have been introduced as a modeling environment for solving large‐scale and complex transportation problems. A constrained system optimum combined trip distribution and assignment problem was selected to demonstrate the applicability of the cellular automata approach over classical mixed integer formulation. A mathematical formulation for the selected problem has been developed and a methodology for applying cellular automata has been presented. A numerical example network was used to illustrate the potential for using cellular automata as a modeling environment for solving optimization problems.}, number={6}, journal={COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING}, author={ElDessouki, WM and Fathi, Y and Rouphail, N}, year={2001}, month={Nov}, pages={384–398} }
 @article{taylor_carrano_fathi_2000, title={Parametric design and optimization for a nonlinear precision X-Y microstage}, volume={19}, ISSN={["0278-6125"]}, DOI={10.1016/S0278-6125(01)80002-9}, abstractNote={A new micropositioning system based on the kinematic coupling principle is shown to offer advantages with respect to resolution, accuracy, precision, and position repeatability while maintaining full two-dimensional motion control. This new system is shown to have a mechanical amplification (leverage) that can allow up to several times increase in the effective positioning resolution of the actuators driving the kinematic coupling mechanism. However, the magnitude of the leverage is not homogeneous over the entire working envelope of the mechanism. Furthermore, in some areas, the magnitude of the leverage is shown to be very sensitive to perturbations in the design parameters. This paper provides a discussion of the parameter design analysis for the proposed system using a methodology based on design of experiments and nonlinear mathematical programming. Using an indicator developed for this purpose, a response surface for the mechanical advantage is obtained and optimal design areas are identified. More importantly, this analysis proves to be flexible enough in searching for the set of parameters that would achieve any particular target on the level of performance, while presenting the least sensitivity to manufacturing noise. This allows for manufacture of variations of the proposed mechanism within feasible manufacturing tolerances and costs. A case study is also presented as an illustration of one real application in manufacturing design. Additionally, potential areas of implementation, such as precision assembly and rapid prototyping, have been identified.}, number={4}, journal={JOURNAL OF MANUFACTURING SYSTEMS}, author={Taylor, JB and Carrano, AL and Fathi, Y}, year={2000}, pages={229–238} }
 @article{elmaghraby_fathi_taner_1999, title={On the sensitivity of project variability to activity mean duration}, volume={62}, ISSN={["0925-5273"]}, DOI={10.1016/S0925-5273(98)00241-2}, abstractNote={Traditionally the `importance' of an activity in the PERT model of projects is measured by its `criticality index', which is defined as the probability that the activity will be on the longest path. An insightful discussion by Williams (1992, Journal of Operational Research Society 43, 353–357) revealed that the classical criticality index is not always informative or intuitively appealing. In a recent study by Cho and Yum (1997, International Journal of Production Research 35, 2737–2757), a new `Uncertainty Importance Measure' is defined to measure the effect of the variability in an activity duration on the variability of the overall project duration. They propose Taguchi's sampling technique as a method for analyzing the network. The main contribution of this paper is to study the impact of changing the mean duration of an activity on the variability of the project duration. On the way to accomplish this, we further investigate the accuracy of Taguchi's sampling method for approximating the mean and standard deviation of the project duration, and propose steps that could result in computational savings in large networks.}, number={3}, journal={INTERNATIONAL JOURNAL OF PRODUCTION ECONOMICS}, author={Elmaghraby, SE and Fathi, Y and Taner, MR}, year={1999}, month={Sep}, pages={219–232} }
 @article{koksal_smith_fathi_lu_mcgregor_1998, title={A case study in off-line quality control: characterization and optimization of batch dyeing process design}, volume={16}, ISSN={["0267-5730"]}, DOI={10.1504/IJTM.1998.002676}, abstractNote={A method is provided and demonstrated for robust design of the batch dyeing process. This method is used to identify optimal batch dyeing process parameter settings, which produce target colour with the least colour variation within and among dyed fabric pieces. The robust design problem is defined in terms of the design objectives, control factors and noise factors. Performance measures are presented to evaluate mean and dispersion characteristics of the dyeing output. Design and conduct of experiments are discussed for developing empirical models of the performance measures, and these models are developed for the study case. The robust design problem is formulated and solved as a nonlinear programming problem. Confirmation of results and iterative use of the proposed design method are discussed.}, number={4-6}, journal={INTERNATIONAL JOURNAL OF TECHNOLOGY MANAGEMENT}, author={Koksal, G and Smith, WA and Fathi, Y and Lu, JCY and McGregor, R}, year={1998}, pages={358–382} }
 @article{koksal_fathi_1998, title={Design of economical noise array experiments for a partially controlled simulation environment}, volume={35}, DOI={10.1016/S0360-8352(98)00157-0}, abstractNote={Design of economical experiments for estimation of a response function's moments in a partially controlled laboratory environment is studied. The noise factors affecting the response are assumed to be statistically independent and normally distributed. It is also assumed that if a factor is set to a specific level in the experimentation, its actual value is also a normally distributed random variable with a smaller variance. Experimental design levels of the factors are found by matching first few moments of the response function calculated from the distributions of the factors, with the moments of that calculated from the distributions of the experimental values of the factors. These levels are evaluated with regard to the performance of appropriate moment estimators of the response. Suggestions are made as to which levels and experimental design should be used for different degrees of control in the experimentation environment.}, number={3-4}, journal={Computers & Industrial Engineering}, author={Koksal, G. and Fathi, Yahya}, year={1998}, pages={555–558} }
 @article{fathi_1997, title={A linear approximation model for the parameter design problem}, volume={97}, ISSN={["0377-2217"]}, DOI={10.1016/S0377-2217(96)00286-X}, abstractNote={We consider the problem of minimizing the variance of a nonlinear function of several random variables, where the decision variables are the mean values of these random variables. This problem arises in the context of robust design of manufactured products and/or manufacturing processes, where the decision variables are the set points for various design components. A nonlinear programming (NLP) model is developed to obtain approximate solutions for this problem. This model is based on a Taylor series expansion of the given function, up to its linear term. A case study pertaining to the design of a coil spring is discussed, and its corresponding NLP model is developed. Using this model, a non-inferior frontier curve is obtained that shows the trade-off between the minimum mass of the coil spring and the minimum variance of its performance characteristic. Results of applying the model to three other case studies are also presented.}, number={3}, journal={EUROPEAN JOURNAL OF OPERATIONAL RESEARCH}, author={Fathi, Y}, year={1997}, month={Mar}, pages={561–570} }
 @article{fathi_mittal_cline_martin_1997, title={Alternative manufacturing sequences and tolerance buildup: A point of view and a case study}, volume={35}, ISSN={["0020-7543"]}, DOI={10.1080/002075497196019}, abstractNote={We consider alternative sequences of operations for manufacturing a given part. Within each sequence, we study the relationship between the unit-to-unit variation in the machined dimensions and the resulting variation in one or more critical dimensions (i.e. tolerance buildup). We propose an objective criterion for comparing these sequences from the point of view of their impact on the tolerance buildup at the critical dimensions. This criterion, which we refer to as the 'total expected loss' (TEL), is based on the concept of continuous quality loss function. We use TEL as well as the tolerance cost to compare alternative sequences for manufacturing a specific part, and present the results.}, number={1}, journal={INTERNATIONAL JOURNAL OF PRODUCTION RESEARCH}, author={Fathi, Y and Mittal, RO and Cline, JE and Martin, PM}, year={1997}, month={Jan}, pages={123–136} }