O. Ooz

56389631400

Publications - 10

Comparison of discrete- and continuous-time models for scheduling waste wood processing facilities

Máté Hegyháti Balazs David O. Ooz

Publication Name: Central European Journal of Operations Research

Publication Date: 2023-09-01

Volume: 31

Issue: 3

Page Range: 853-871

Description:

With the growing significance of environmental awareness, the role of renewable materials and their reuse and recycling possibilities have become increasingly important. Wood is one of the best examples for this, as it is a material that has a variety of primary uses, while also being a prime candidate for reuse and recycling. An important phase in most waste wood value chains is the processing of bulk waste from various sources, usually by means of shredding. This paper presents methods for scheduling the machines in such a waste wood processing facility, where incoming deliveries of different types of wood are processed by a series of treatment and transformation steps to produce shredded wood. Two mathematical models are developed for the problem that both allow overlaps between consecutive steps to optimize resource flow through the system. One of these is a more traditional discrete-time model, while the other is precedence-based and uses continuous-time variables for the timing of the various tasks. Both modeling techniques have their advantages and shortcomings with regard to the ease of integration of further problem-specific parameters and requirements. Next to providing a sound approach for the identified problem class, another aim is to evaluate, which technique suits better for this problem class, and should be used as a basis for extended and integrated cases in the future. Thus, the performance of these models is compared on instances that were randomly generated based on real-world distributions from the literature.

Open Access: Yes

DOI: 10.1007/s10100-023-00852-6

Addressing storage time restrictions in the S-graph scheduling framework

Máté Hegyháti O. Ooz Tibor Holczinger

Publication Name: Optimization and Engineering

Publication Date: 2021-12-01

Volume: 22

Issue: 4

Page Range: 2679-2706

Description:

Storage planning and utilization are among the most important considerations of practical batch process scheduling. Modeling the available storage options appropriately can be crucial in order to find practically applicable solutions with the best objective value. In general, there are two main limitations on storage: capacity and time. This paper focuses on the latter and investigates different techniques to tackle limited storage time within the S-graph framework. The S-graph framework is a collection of combinatorial algorithms and a directed graph based model that has been introduced three decades ago and has been under development ever since. In this work, several options for addressing storage time limitations within the framework were implemented and tested for efficiency. The empirical results over a huge number of tests have unequivocally favored one of the approaches, which will be applied in later developments.

Open Access: Yes

DOI: 10.1007/s11081-020-09548-1

Robust scheduling of waste wood processing plants with uncertain delivery sources and quality

Máté Hegyháti Balazs David O. Ooz

Publication Name: Sustainability Switzerland

Publication Date: 2021-05-01

Volume: 13

Issue: 9

Page Range: Unknown

Description:

While the study of reverse wood value chains has become an important topic recently, optimization-focused studies usually consider network-level problems and decisions, and do not address the individual processes in the network. In the case of waste wood, one such important process is the scheduling of the various machines in a waste wood processing facility to treat incoming wood deliveries with multiple sources and varying quality. This paper proposes a robust multi-objective mixed-integer linear programming model for the optimization of this process that considers the uncertain origins and compositions of the incoming deliveries, while aiming to minimize both lateness and energy consumption. An exhaustive study is performed on instance sets of different sizes and structures to show the efficiency and the limits of the proposed model both in single-and multi-objective cases.

Open Access: Yes

DOI: 10.3390/su13095007

Minimizing Freshwater Usage in Batch Process Scheduling: S-Graph Approach

Máté Hegyháti O. Ooz Dominic C.Y. Foo

Publication Name: Process Integration and Optimization for Sustainability

Publication Date: 2021-03-01

Volume: 5

Issue: 1

Page Range: 31-42

Description:

Water is one of the most important natural resources of life. While it is considerably cheap and vastly available currently, except for extreme locations, this is not guaranteed in the future. Being provident with water has multitude of advantages in both short and long term. Using less clean water not only brings immediate financial benefits, it simultaneously reduces wastewater production, related treatment costs, and the impact on the environment. Reducing the water footprint of a batch system is not a trivial task, as water sources and sinks need to be matched not only in quantity and quality, but in time as well. In this paper, the S-graph scheduling framework is extended to address simultaneous scheduling and water minimization in batch processing systems. The proposed approach tackles truly batch processes with a single contaminant, and allows only a single water source to be reused for each sink. The presented algorithm and S-graph extension have been implemented and tested on various case studies from the literature. The results of this paper provide an opportunity for further extensions to address a wider range of problems with multiple contaminants, semi-continuous behavior, cyclic operations, etc.

Open Access: Yes

DOI: 10.1007/s41660-020-00142-7

SCHEDULING OF WASTE WOOD PROCESSING FACILITIES WITH OVERLAPPING JOBS

Máté Hegyháti Balazs David O. Ooz

Publication Name: Proceedings of the 16th International Symposium on Operational Research in Slovenia Sor 2021

Publication Date: 2021-01-01

Volume: Unknown

Issue: Unknown

Page Range: 321-326

Description:

An important phase in most waste wood value chains is the processing of bulk waste from various sources, usually by means of shredding. This paper presents a method for scheduling the machines in such a waste wood processing facility, where incoming deliveries of different types of wood are processed by a series of treatment and transformation steps to produce shredded wood. A mathematical model is presented for the problem, that allows overlaps between consecutive steps to optimize resource flow through the system. The efficiency of the model is presented on randomly generated instances.

Open Access: Yes

DOI: DOI not available

Scheduling approach for on-site jobs of service providers

Máté Hegyháti O. Ooz Tibor Holczinger

Publication Name: Flexible Services and Manufacturing Journal

Publication Date: 2020-12-01

Volume: 32

Issue: 4

Page Range: 913-948

Description:

Nowadays the successful operation of a company is unimaginable without fast and reliable communication. As a result, so-called Communication Service Providers play an important role in today’s business life. Their orders have to be carried out promptly and dependably, let them be requests for new installations, modifications, or maintenance tasks. These orders have to be performed at different locations and they often have deadlines or strict starting times. Violating such a timing requirement usually implies penalties. In this paper, scheduling problems arising at a Hungarian service provider are examined. At this company, orders are decomposed into smaller tasks, which can be performed by specially trained personnel. Transportation of these specialists contributes a lot to the costs and to the complexity of their scheduling, as well. The goal is to minimize the overall cost of satisfying all orders within the given time horizon with the available assets of the company. The proposed approach relies on the S-graph framework, which has been applied to various production scheduling problems in the literature. In addition to an unambiguous and sound S-graph model of the examined problem, slight modifications of the scheduling algorithms for cost minimization, and new bounding methods have been developed. Several of such bounds have been provided and tested for performance and scalability over a large number of generated examples. The sensitivity of the approach for certain problem features has also been examined.

Open Access: Yes

DOI: 10.1007/s10696-019-09359-2

Scheduling a forge with due dates and die deterioration

Máté Hegyháti O. Ooz B. Ferenczi

Publication Name: Annals of Operations Research

Publication Date: 2020-02-01

Volume: 285

Issue: 1-2

Page Range: 353-367

Description:

In this paper a new scheduling problem is presented, which originates from the steel processing industry. The optimal scheduling of a steel forge is investigated with the goal of minimizing setup and storage costs under strict deadlines and special resource constraints. The main distinctive feature of the problem is the deterioration of some equipment, in this case, the so-called forging dies. While the aging effect has been widely investigated in scheduling approaches, where production speed decreases through time, durability deterioration caused by equipment setup has not been addressed yet. In this paper a mixed-integer linear programming model is proposed for solving the problem. The model uses a uniform discrete time representation and resource-balance constraints based on the resource–task network model formulation method. The proposed method was tested on 3-week long schedules based on real industrial scenarios. Computational results show that the approach is able to provide optimal short-term schedules in reasonable time.

Open Access: Yes

DOI: 10.1007/s10479-019-03336-6

A study on solving single stage batch process scheduling problems with an evolutionary algorithm featuring bacterial mutations

F. Hatwágner Máté Hegyháti O. Ooz

Publication Name: Lecture Notes in Computer Science Including Subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics

Publication Date: 2018-01-01

Volume: 10841 LNAI

Issue: Unknown

Page Range: 386-394

Description:

The short term scheduling of batch processes is an active research field of chemical engineering, that has been addressed by many different techniques over the last decades. These approaches, however, are unable to solve long-term scheduling problems due their size, and the vast number of discrete decisions they entail. Evolutionary algorithms already proved to be efficient for some classes of large scheduling problems, and recently, the utilization of bacterial mutations has shown promising results on other fields. In this paper, an evolutionary algorithm featuring bacterial mutation is introduced to solve a case study of a single stage product scheduling problem. The solution performance of the algorithm was compared to a method from the literature. The results indicate that the proposed approach can find the optimal solution under relatively short execution times.

Open Access: Yes

DOI: 10.1007/978-3-319-91253-0_36

An S-graph based approach for multi-mode resource-constrained project scheduling with time-varying resource capacities

Máté Hegyháti O. Ooz

Publication Name: 23rd International Congress of Chemical and Process Engineering Chisa 2018 and 21st Conference on Process Integration Modelling and Optimisation for Energy Saving and Pollution Reduction Pres 2018

Publication Date: 2018-01-01

Volume: 2

Issue: Unknown

Page Range: 955

Description:

No description provided

Open Access: Yes

DOI: DOI not available

An S-graph based approach for multi-mode resource-constrained project scheduling with time-varying resource capacities

Máté Hegyháti O. Ooz

Publication Name: Chemical Engineering Transactions

Publication Date: 2018-01-01

Volume: 70

Issue: Unknown

Page Range: 1165-1170

Description:

The Resource-Constrained Project Scheduling Problem (RCPSP) is a general problem class of scheduling problems. It even contains the well-known job shop scheduling problem as a special case. In these problems, jobs demand different amounts from multiple resources at once. The goal is to minimize completion time while satisfying resource capacity constraints throughout the schedule. The RCPSP has several variations and generalizations, one of which is the multi-mode problem. Multiple operation modes are given for jobs, differing in resource usages and execution times. Another generalization is where resources have time-varying capacities instead of a constant limit. The S-graph framework was developed for batch process scheduling and used successfully in various applications. The advantages of this approach motivate research to extend its capabilities to more general problem classes and apply it in various specialized case studies. The authors have previously presented an extension of the S-graph framework for RCPSP and its multi-mode generalization. In this work, a further extension is proposed for handling time-varying capacities. The method relies on a model transformation technique and recent algorithmic developments of the framework.

Open Access: Yes

DOI: 10.3303/CET1870195