Arslan M. Örnek

Yasar University · Industrial Engineering

In today’s competitive market, the pressure on organizations to find ways to create value for customers and meet their requirements becomes stronger. In this manner, clothing manufacturers focus on the production of various products with low stock to minimize their costs. In the garment industry, assembly lines are commonly used production systems...

To address the increasing demand for air transportation, the management, allocation, and efficient utilization of limited airport resources, such as bridge-equipped gates, are of paramount importance to improve the efficiency of the air transportation system. Bridge-equipped gates are scarce and immobile resources have a significant impact on airpo...

This study solves a one-dimensional cutting stock problem with multiple stock lengths. It is applied in a manufacturing setting where rolls of steel rods of different lengths are cut according to customer requirements. The one-dimensional cutting stock problem (CSP) is an NP-hard problem, including discrete demands and capacitated planning objectiv...

In view of the rapid increase in the volume of air traffic, optimization of airport management has recently gained a great deal of attention to be able to increase the airport capacity and efficiently use scarce resources, namely gates. Improper assignment of gates causes flight delays, inefficient usage of scarce resources, customers’ dissatisfact...

The assignment of flights to appropriate gates is a complex combinatorial optimization problem that airport managers have to deal with every day. It is an important decision-making problem involving multiple and conflicting objectives. Considering the different stakeholders of the problem, a multi-objective airport gate assignment problem is propos...

Companies use different production policies to ensure customer demands are satisfied in time. To track the performance of production policies some important Key Performance Indicators related to production control and management are On-Time Delivery (OTD), machine or line productivity (OEE – Overall Equipment Efficiency), optimization of inventory...

Flight-gate assignment problems are complex real world problems involving different constraints. Some of these constraints include plane-gate eligibility, assigning planes of the same airline and planes getting service from the same ground handling companies to adjacent gates, buffers for changes in flight schedules, night stand flights, priority o...

Since distribution activities have great importance for firms, supply management is a widely studied concept in many sectors. This study demonstrates an application of a Capacitated Vehicle Routing Problem with Time Windows (CVRPTW). The problem is in the form of a fixed destination multi depots visited by multi-travelling salesmen and the distance...

This paper aims to develop an optimal real-life energy-efficient design for a production plant within the concept of the circular economy. The problem is to install a Heat Recovery System (HRS) that utilizes the hot oil used by the compressors to heat the water for the central heating system. To achieve the desired level of energy efficiency this d...

In this paper, a real-life single machine job scheduling problem with sequence-dependent setup times of a hood manufacturer company is addressed to minimize total weighted tardiness of the jobs with given due dates. Initially, a mixed-integer linear programming model is developed for the problem. Since the problem is NP-hard, heuristic algorithms a...

Permutation flow shop scheduling problem is a well-known problem in the scheduling literature. Even though various multi-objective permutation flowshop scheduling problems have been studied in the literature, energy consumption consideration in scheduling is still very seldom. In this paper, we consider a bi-objective permutation flowshop schedulin...

Check-in counters have a great impact on the quality of service for airports. It is airport management's responsibility to provide check-in counters to airlines. Each check-in group (i.e., flights sharing the same resources) has a counter demand and this gives rise to a counter assignment problem. This is due to a number of objectives and constrain...

Due to economical and/or geographical constraints, most of the time overseas containers cannot be directly shipped to their destinations. These containers visit transhipment ports where they are first unloaded and temporarily stored and then loaded onto smaller vessels (feeders) to be transported to their final destinations. The assignment of these...

Manufacturing Resources Planning (MRPII) systems are unable to prevent capacity problems occurring on the shop floor because of the fixed lead time and backward scheduling logic. For this reason, a new breed of concepts called APS (Advanced Planning and Scheduling) systems emerged which include finite capacity planning at the shop floor level throu...

In this paper, the problem of balancing and cyclic scheduling of flexible mixed model assembly lines with parallel stations is studied. To exploit the connection between balancing and cyclic scheduling problems for an efficient line management, they are considered simultaneously. A novel constraint programming model including problem specific symme...

Since the basic reasoning of Manufacturing Resources Planning (MRPII) systems is flawed, a new breed of concepts called Advanced Planning and Scheduling systems (APS) have recently emerged to overcome the problems occurring on the shop floor. In this study, we develop improved and extended mixed integer programming formulations for APS systems at t...

In a so-called multi-period yarn dyeing and batching problem, we try to determine the optimal batching of customer orders to be dyed in dye machines in each shift to minimize total lateness and earliness costs. In addition to weight, production quantity and volume capacity of the machines, there is a set of technical dyeing interaction constraints...

In this paper, we study flexible mixed model assembly lines with serially connected stages where stages may have one or more parallel stations. Station parallelism in flexible mixed model assembly lines improves system reliability and enables rapid adaptability to customer demand fluctuations. However, in order to effectively manage such lines unde...

Mixed model assembly line literature involves two problems: balancing and model sequencing. The general tendency in current studies is to deal with these problems in different time frames. However, in today’s competitive market, the mixed model assembly line balancing problem has been turned into an operational problem. In this paper, we propose mi...

Although Material Requirements Planning (MRP) is the most widely used production planning tool in today’s manufacturing companies, its inability to perform an exhaustive capacity planning, lack of a comprehensive and integrated shop floor extension and using constant and inflated lead times necessitate intelligent methods for developing cost effect...

Transfer lines represent the basic manufacturing system of many high volume production systems. Analysis and understanding of transfer lines are of great importance to improve design and operation performance of many manufacturing systems. Majority of research on the throughput of transfer lines concentrate on the steady state results. Due to the c...

Transfer lines represent the basic manufacturing system of many high volume production systems. Analysis and understanding of transfer lines are of great importance to improve design and operation performance of many manufacturing systems. Majority of research on the throughput of transfer lines concentrate on the steady state results. Due to the c...

We consider Simultaneous Balancing and Scheduling of Flexible Mixed Model Assembly Lines with Sequence-Dependent Setup Times (SBSFMMAL-SDST). We propose alternate Mixed Integer Programming (MIP) and Constraint Programming (CP) formulations. Our experiments show that while the MIP models could not solve relatively small instances, the CP approach se...

In a recent paper, Chen and Ji [Chen, K., Ji, P., 2007. A mixed integer programming model for advanced planning and scheduling (APS). European Journal of Operational Research 181, 515-522] develop a mixed integer programming model for advanced planning and scheduling problem that considers capacity constraints and precedence relations between the o...

In this paper, we propose a mixed integer programming (MIP) model for a multi-level multi resource capacitated lot sizing and scheduling problem with a set of constraints to track dependent demand balances, that is, the amount left over after allocating the available inventory to the dependent demands. A part of this leftover amount may be kept as...

Overseas containers sometimes cannot be directly shipped to their destinations, but first unloaded, temporarily stored and then loaded onto smaller vessels at interim ports to save cost and/or to transport them to their final destinations directly. The assignment of these transshipment containers to vessels necessitates several measures to be taken...

Disruptions in material plans due to unrealistic schedules and frequent plan revisions are common symptoms of a phenomenon generally referred to as nervousness or schedule instability in literature. A number of instability measures had been proposed so far. However, none of them deals with instability measurement comprehensively. An appropriate mea...

In this paper we study a multi-product lot streaming problem in a stochastic job shop with equal and discrete sublots. The problem involves splitting order quantities of different products into different number of equal sublots (NES) and analyzing the effects of sublot-related transportation queue disciplines (TRQD) for different performance measur...

We consider minimum-cost scheduling of different vehicle types on a predetermined set of one-way trips. Trips have predetermined ready times, deadlines and associated demands. All trips must be performed. The total time of operations on any vehicle is limited. We develop a mixed integer model to find the optimal number of vehicles at a minimum cost...

Lot streaming is a technique that splits a production lot consisting of identical items into sublots to improve the performance of a multistage production system by overlapping the sublots on successive machines. In this study, a single-product multistage stochastic flow shop problem with consistent sublot types and discrete sublot sizes is conside...

In this paper we analyze and evaluate the effects of some pre-defined process parameters on the performance of a manufacturing system. These parameters include two different plant layout types, namely functional layout (FL) and cellular manufacturing layout (CL), as well as scheduling rule, machine downtimes, batch sizes, and transporter (interstag...

We consider the problem of determining realistic and easy-to-schedule lot sizes in a multiproduct, multistage manufacturing environment. We concentrate on a specific type of production, namely, flow shop type production. The model developed consists of two parts, lot sizing problem and scheduling problem. In lot sizing problem, we employ binary int...

Lot streaming is the process that splits the production lot into sublots and streams these sublots among the machines with regard to some performance criteria. A performance criterion can be time-based (e.g., makespan) or cost-based (e.g., total cost), while some studies consider both of them together. In lot streaming problems, the production syst...

Material requirements planning (MRP) is a basic tool for performing detailed material planning function in the manufacture of component parts and their assembly into finished items. MRP's managerial objective is to provide ‘the right part at the right time’ to meet the schedules for completed products. However satisfying end customer demands faster...

In most manufacturing systems, a number of production stages are involved between which some in-process inventory usually occurs. This inventory imposes a further cost on the overall system, not only in terms of investment charges but also shop floor congestion, additional material handling charges and loss of floor space. In attempting to optimise...

One of the many factors involved in the study of [`]in-process' inventories is that of the energy input. During the last decade this factor has assumed an ever increasingly important rôle as supplies fall and costs escalate. Industry has been forced to adopt ways of improving its energy utilisation efficiency but this has been largely in the area o...

A new improved metric composed of linear combination of four sub-instability measures is proposed for measuring schedule instability in multi -item MRP environments. It separates quantity and timing changes for both scheduled receipts (SR) and planned orders (POR). The new metric is tested by a detailed numerical example and results of the simulati...

Thesis (Ph. D.)--University of Wales, 1980.