Haldun Sural

Middle East Technical University, Industrial Engineering, Faculty Member

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Haldun Süral
Industrial Engineering, Middle East Technical University (METU)
hsural@metu.edu.tr / +90 312-210-4685

He is professor at the IE Department of METU, Ankara, Turkey. His work experience includes teaching and research positions at INSEAD (France), and UW and WLU (Canada). His research works range from supply/production/distribution network design to restructuring a large humanitarian aid organization and waste management system design. He is an area editor of INFOR: Information Systems and Operational Research, a member of the advisory board of OR Spectrum, and served at the past editorial board of Turkish Journal of IE. He is past president of the OR Society of Turkey. His research interests include methodology, modeling, and applications in OR and history of OR in Turkey.
Supervisors: Omer Kirca, Suna Kondakci, and Nesim Erkip

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Papers by Haldun Sural

Teaching Note —Forecasting Beer Demand at Anadolu Efes

by S. Özpeynirci and Haldun Sural

INFORMS Transactions on Education, 2010

Lagrangean relaxation based heuristics for lot sizing with setup times

by Meltem Denizel and Haldun Sural

European Journal of Operational Research, 2009

We consider a lot sizing problem with setup times where the objective is to minimize the total in... more We consider a lot sizing problem with setup times where the objective is to minimize the total inventory carrying cost only. The demand is dynamic over time and there is a single resource of limited capacity. We show that the approaches implemented in the literature for more general versions of the problem do not perform well in this case. We examine the Lagrangean relaxation (LR) of demand constraints in a strong reformulation of the problem. We then design a primal heuristic to generate upper bounds and combine it with the LR problem within a subgradient optimization procedure. We also develop a simple branch and bound heuristic to solve the problem. Computational results on test problems taken from the literature show that our relaxation procedure produces consistently better solutions than the previously developed heuristics in the literature.

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An Evolutionary Approach for the TSP and the TSP with Backhauls

by Nur Ozdemirel and Haldun Sural

Evolutionary Learning and Optimization, 2010

Page 1. Chapter 15 An Evolutionary Approach for the TSP and the TSP with Backhauls Haldun Süral, ... more

Equivalence of the LP relaxations of two strong formulations for the capacitated lot-sizing problem with setup times

by Meltem Denizel and Haldun Sural

Or Spektrum, 2008

The multi-item Capacitated Lot-Sizing Problem (CLSP) has been widely studied in the literature du... more The multi-item Capacitated Lot-Sizing Problem (CLSP) has been widely studied in the literature due to its relevance to practice, such as its application in constructing a master production schedule. The problem becomes more realistic with the incorporation of setup times since they may use up significant amounts of the available resource capacity. In this paper, we present a proof to show the linear equivalence of the Shortest Path (SP) formulation and the Transportation Problem (TP) formulation for CLSP with setup costs and times. Our proof is based on a linear transformation from TP to SP and vice versa. In our proof, we explicitly consider the case when there is no demand for an item in a period, a case that is frequently observed in the real world and in test problems in the literature. The equivalence result in this paper has an impact on the choice of model formulation and the development of solution procedures.

The one-warehouse multiretailer problem with an order-up-to level inventory policy

by Meltem Denizel and Haldun Sural

Naval Research Logistics, 2010

We consider a two-level system in which a warehouse manages the inventories of multiple retailers... more We consider a two-level system in which a warehouse manages the inventories of multiple retailers. Each retailer employs an order-up-to level inventory policy over T periods and faces an external demand which is dynamic and known. A retailer's inventory should be raised to its maximum limit when replenished. The problem is to jointly decide on replenishment times and quantities of warehouse and retailers so as to minimize the total costs in the system. Unlike the case in the single level lot-sizing problem, we cannot assume that the initial inventory will be zero without loss of generality. We propose a strong mixed integer program formulation for the problem with zero and nonzero initial inventories at the warehouse. The strong formulation for the zero initial inventory case has only T binary variables and represents the convex hull of the feasible region of the problem when there is only one retailer. Computational results with a state-of-the art solver reveal that our formulations are very effective in solving large-size instances to optimality. © 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010

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Effective network formulations for lot sizing with backlogging in two-level serial supply chains

IIE Transactions, 2015

ABSTRACT This study considers the serial lot sizing problems with backlogging in two-level supply... more ABSTRACT This study considers the serial lot sizing problems with backlogging in two-level supply chains to determine when and how much to order at a warehouse and ship to a retailer over a T-period planning horizon so that the external known demand occurring at the retailer is satisfied and the total cost at all levels is minimized. In particular, the uncapacitated two-level serial lot sizing problem with backlogging and the two-level serial lot sizing problem with cargo capacity and backlogging are formulated using effective shortest path network representations, which define the convex hull of their feasible solutions. These representations lead to efficient algorithms with O(T^3) time for the uncapacitated problem and O(T^6) time for the capacitated problem. Furthermore, a tight reformulation with O(T^3) variables and O(T^2) constraints (resp. O(T^6) variables and O(T^5) constraints) is proposed for the uncapacitated (resp. capacitated) problem.

A New Approach to Heat Exchanger Network Synthesis Problem

Network Redesign in Turkey: The Supply, Production, and Distribution of Malt and Beer

by Murat Köksalan, Haldun Sural, and S. Özpeynirci

International Series in Operations Research & Management Science, 2012

A Genetic Algorithm for the Traveling Salesman Problem with Pickup and Delivery Using Depot Removal and Insertion Moves

Lecture Notes in Computer Science, 2010

In this work, we consider the Traveling Salesman Problem with Pickup and Delivery (TSPPD), which ... more In this work, we consider the Traveling Salesman Problem with Pickup and Delivery (TSPPD), which is an extension of the well-known NP-hard Traveling Salesman Problem. We propose a Genetic Algorithm (GA) based on a specially tailored tour improvement procedure for the TSPPD. Computational experiments are reported on the test instances taken from the literature. The experimental results suggest that the

Gezgin satıcı problemi (Traveling salesman problem)

Gezgin Sat›c› Problemi'nde (GSP) amaç, bir sat›c›-n›n, bulundu¤u flehirden bafllay›p, her flehre ... more Gezgin Sat›c› Problemi'nde (GSP) amaç, bir sat›c›-n›n, bulundu¤u flehirden bafllay›p, her flehre sadece bir kez u¤rad›ktan sonra bafllad›¤› flehre geri dönen en k›sa turu bulmakt›r. Herhangi iki flehir aras›nda bir yol oldu¤unu ve o yolun uzunlu¤unu bildi¤imizi varsay›yoruz.

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A model and an LP-based rounding heuristic for the facility layout problem

Teaching Note-Forecasting Beer Demand at Anadolu Efes

by Murat Köksalan and Haldun Sural

Türkiye’de Yöneylem Araştırması: Sistem Bilimleri Araştırma Enstitüsü (SİBAREN)

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The order picking problem in fishbone aisle warehouses

Case-Forecasting Beer Demand at Anadolu Efes

by Murat Köksalan and Haldun Sural

Tight formulations for the two and three level serial lot-sizing problems

Coordinating inventory and transportation in vendor managed systems

An Evolutionary Approach for the TSP and the TSP with Backhauls

Evolutionary Learning and Optimization, 2010

Page 1. Chapter 15 An Evolutionary Approach for the TSP and the TSP with Backhauls Haldun Süral, ... more

A note on ?The general lot sizing and scheduling problem?

OR Spectrum, 2005

Page 1. DOI: 10.1007/s00291-004-0181-7 OR Spectrum (2005) 27: 145146 c Springer-Verlag 2005 A no... more

The Weber problem in congested regions with entry and exit points

by Haldun Sural and Cem İyigün

Computers & Operations Research, 2014

ABSTRACT The Weber problem is about finding a facility location on a plane such that the total we... more ABSTRACT The Weber problem is about finding a facility location on a plane such that the total weighted distance to a set of given demand points is minimized. The facility location and access routes to the facility can be restricted if the Weber problem contains congested regions, some arbitrary shaped polygonal areas on the plane, where location of a facility is forbidden and traveling is allowed at an additional fixed cost. Traveling through congested regions may also be limited to certain entry and exit points (or gates). It is shown that the restricted Weber problem is non-convex and nonlinear under Euclidean distance metric which justifies using heuristic approaches. We develop an evolutionary algorithm modified with variable neighborhood search to solve the problem. The algorithm is applied on test instances derived from the literature and the computational results are presented.

Teaching Note —Forecasting Beer Demand at Anadolu Efes

by S. Özpeynirci and Haldun Sural

INFORMS Transactions on Education, 2010

Lagrangean relaxation based heuristics for lot sizing with setup times

by Meltem Denizel and Haldun Sural

European Journal of Operational Research, 2009

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An Evolutionary Approach for the TSP and the TSP with Backhauls

by Nur Ozdemirel and Haldun Sural

Evolutionary Learning and Optimization, 2010

Page 1. Chapter 15 An Evolutionary Approach for the TSP and the TSP with Backhauls Haldun Süral, ... more

Equivalence of the LP relaxations of two strong formulations for the capacitated lot-sizing problem with setup times