Thesis Topics

The Department of Logisitics is currently expressly not offering any more thesis topics except the ones listed below. If you are interested, please read the hints on how to write a thesis with the Department of Logistics and contact the supervisor mentioned below.

Bachelor or Master Topics supervised by Dr. Chankov

Crowd Logistics: Crowdsourcing Potential for the Logistics Industry
Crowdsourcing is an increasingly used concept in a variety of fields, mainly within the scope of the sharing/collaborative economy. Crowdsourcing practices have been successfully used in other key economic fields such as: professional/personal services (e.g. Craigslist), pre-owned goods (e.g. eBay), custom products (e.g. Etsy), funding (e.g. Kickstarter), money-lending (e.g. Kiva) or transportation (e.g. Uber). While companies like Uber are already well-established in the passenger transportation area, crowd logistics (e.g. crowdsourced goods delivery, crowdshipping, or shared storage) has only recently received interest in both theory and practice. Amazon has started its initiative in Seattle September 2015 through Amazon Flex and Uber is already operating a delivery service since April 2015 named UberRUSH.Crowdsourcing could potentially be very suitable for logistics services. For example, it can help for last-mile shipments, which are becoming more and more problematic mostly due to the high growth of e-commerce. The aim of this study is to investigate crowdsourcing applications for logistics services. The course of research can involve conducting a simulation study, conducing an online survey to collect data or extensive online search to identify business models for crowd logistics. A good starting point is Rougès and Montreuil (2014).
Dr. Chankov
Crowdsourced Delivery: A Detailed Simulation Study for Last Mile Distribution
Crowdsourcing is an increasingly used concept in a variety of fields, mainly within the scope of the sharing/collaborative economy. Crowdsourcing practices have been successfully used in other key economic fields such as: accommodation (Airbnb), transportation (e.g. Uber), professional/personal services (e.g. Craigslist), pre-owned goods (e.g. eBay), custom products (e.g. Etsy), funding (e.g. Kickstarter) or money-lending (e.g. Kiva). While companies like Uber are already well-established in the passenger transportation area, crowd logistics (e.g. crowdsourced goods delivery, crowdshipping, or shared storage) has only recently received interest in both theory and practice. Amazon has started its initiative in Seattle September 2015 through Amazon Flex and Uber is already operating a delivery service since April 2015 named UberRUSH.Crowdsourced delivery is considered a possible solution to the last-mile on-demand delivery challenge. The purpose of this study is to investigate the performance of the crowdsourced last-mile delivery with regard to service level and assets utilization. An existing agent-based simulation model can be further developed in order to study the effect of parameters such as:

  • supply/demand ratio, the ratio between the number of crowd couriers delivering packages and the number of packages
  • maximum detour time accepted by crowd couriers
  • customer order density within a city
  • flow of commuters within a city
  • type of customer orders.

A good starting point is Rougès and Montreuil (2014). Please contact me for recommended reading and more details on the model .

Dr. Chankov
Crowdsourcing Potential for University Campuses
Crowdsourcing is an increasingly used concept in a variety of fields, mainly within the scope of the sharing/collaborative economy. Crowdsourcing practices have been successfully used in other key economic fields such as: accommodation (Airbnb), transportation (e.g. Uber), professional/personal services (e.g. Craigslist), pre-owned goods (e.g. eBay), custom products (e.g. Etsy), funding (e.g. Kickstarter) or money-lending (e.g. Kiva).Crowdsourcing could potentially be very suitable for sharing under-utilized assets at a university campus. The student body on any campus provides a group of people who on the one hand share common interests and needs and on the other complement each other’s interests and needs. Students with untapped talent are looking to learn, students with limited time are looking for ways to save time, and students with limited resources are looking for ways to gain some income.The purpose of this thesis is to explore crowdsourcing applications at university campuses, and explore further crowdsourcing opportunities for sharing both goods (e.g., books, bikes, rooms, etc.) and services (e.g., package/food delivery, app development, haircut, etc.). The course of research can involve conducing an online survey to collect data, an extensive online search to identify business models for crowd logistics and/or a simulation study to test crowdsourcing potential.
Dr. Chankov
Crowdsourcing and Sharing Economy
Crowdsourcing is an increasingly used concept in a variety of fields, mainly within the scope of the sharing/collaborative economy. Crowdsourcing practices have been successfully used in other key economic fields such as: accommodation (Airbnb), transportation (e.g. Uber), professional/personal services (e.g. Craigslist), pre-owned goods (e.g. eBay), custom products (e.g. Etsy), funding (e.g. Kickstarter) or money-lending (e.g. Kiva). While companies like Uber are already well-established in the passenger transportation area, crowd logistics (e.g. crowdsourced goods delivery, crowdshipping, or shared storage) has only recently received interest in both theory and practice. Amazon has started its initiative in Seattle September 2015 through Amazon Flex and Uber is already operating a delivery service since April 2015 named UberRUSH.Any topic for the general sharing/collaborative economy (e.g. Airbnb) is possible, you can come up with your own ideas.
 Dr. Chankov
Last-Mile Distribution: Future Trends
You can formulate your own topic and course of research. A good starting point is this DHL Report (pages 24-28).
Dr. Chankov
Omni-Channel Logistics: Case Study Analysis
You can formulate your own topic and course of research. A good starting point is this DHL Report.
Dr. Chankov
Triggers and Effects of Synchronization in Supply Chains – Minimal Model Investigation
Synchronization in a broader sense means aligning a certain behavior or state over time. In the physical world, two systems can spontaneously synchronize with respect to each other even if there are only small physical interactions. Up to now it is not fully understood how synchronization affects supply chains: Does a spontaneous synchronization also occur in supply chains? If so, what triggers it and how does it influence the achievement of the logistics objectives and the robustness of the processes?
The purpose of this thesis is to study synchronization phenomena present in supply chains. Minimal models can be used to investigate the triggers and effects of those phenomena occurring in supply chains.  By applying synchronization measures to the models, the thesis will firstly examine the relation between synchronization and the supply chain’s core characteristics (e.g., design, structure, operations and control strategy, arrival times (distribution), processing time (distribution)). Secondly, it will research the link between synchronization and the supply chain performance (e.g., lateness, inventory levels) and robustness (e.g., deviations in performance due to system disturbances), thus drawing conclusions for the consequences that synchronization has on supply chains. A good starting point is:

  • [DOI] S. M. Chankov, M. Hütt, and J. Bendul, “Synchronization in manufacturing systems: quantification and relation to logistics performance,” International journal of production research, 2016.
    [Bibtex]
    @article{Chankov2016a,
    author = {Chankov, Stanislav M. and H{\"u}tt, Marc-Thorsten and Bendul, Julia},
    title = {Synchronization in manufacturing systems: quantification and relation to logistics performance},
    journal = {International Journal of Production Research},
    doi = {10.1080/00207543.2016.1165876},
    URL = {http://dx.doi.org/10.1080/00207543.2016.1165876},
    eprint = {http://dx.doi.org/10.1080/00207543.2016.1165876},
    year={2016},
    abstract = {The term 'synchronization' in manufacturing refers to the provision of the right components to the subsequent production steps at the right moment in time. It is widely assumed that synchronization is beneficial to the logistics performance of manufacturing systems. However, it has been shown that synchronization phenomena can be detrimental to systems in which they emerge. To study if synchronization phenomena also occur in and affect manufacturing systems' performance, a formal quantification and holistic understanding of the types of synchronization phenomena emerging in manufacturing are needed. This article aims to fill this research gap by developing synchronization measures for manufacturing systems, applying these measures to real-world production feedback data and utilising them to test the assumption about synchronization's beneficial effect on logistics performance. We identify two distinct synchronization types occurring in manufacturing systems, logistics and physics synchronization, and show that they are negatively correlated. Further, we show that logistics synchronization and due date performance exhibit anti-correlation and thus question the assumption that synchronization leads to higher efficiency in manufacturing systems. This article aids production managers in designing and optimising production systems, and supports further empirical research in production planning and control and production system design.},
    }
  • [DOI] S. M. Chankov, G. Malloy, and J. Bendul, “The influence of manufacturing system characteristics on the emergence of logistics synchronization: a simulation study,” in Dynamics in logistics: proceedings of the 5th international conference ldic, 2016 bremen, germany, M. Freitag, H. Kotzab, and J. Pannek, Eds., Cham: Springer International Publishing, 2016, pp. 29-40.
    [Bibtex]
    @inbook{Chankov2016b,
    author="Chankov, Stanislav M. and Malloy, Giovanni and Bendul, Julia",
    editor="Freitag, Michael and Kotzab, Herbert and Pannek, J{\"u}rgen",
    title="The Influence of Manufacturing System Characteristics on the Emergence of Logistics Synchronization: A Simulation Study",
    bookTitle="Dynamics in Logistics: Proceedings of the 5th International Conference LDIC, 2016 Bremen, Germany",
    year="2016",
    publisher="Springer International Publishing",
    address="Cham",
    pages="29--40",
    isbn="978-3-319-45117-6",
    doi="10.1007/978-3-319-45117-6_3",
    url="http://dx.doi.org/10.1007/978-3-319-45117-6_3"
    abstract="The term 'synchronization' in manufacturing refers to the provision of the right components to the subsequent production steps at the right moment in time. It is still unclear how manufacturing system characteristics impact synchronization. Thus, the purpose of this paper is to investigate the effect of manufacturing systems' characteristics on the emergence of logistics synchronization in them. We conduct a discrete-event simulation study to examine the effect of three system characteristics: (1) material flow network architecture, (2) work content variation, and (3) order arrival pattern. Our findings suggest that the material flow network architecture and the work content variation are related to logistics synchronization. Linear manufacturing systems with stable processing times such as flow shops operate at high logistics synchronization levels, while highly connected systems with high variability of processing times such as job shops exhibit lower synchronization levels."
    }
  • [DOI] M. A. Schipper, S. M. Chankov, and J. Bendul, “Synchronization emergence and its effect on performance in queueing systems,” Procedia cirp, vol. 52, pp. 90-95, 2016.
    [Bibtex]
    @article{Schipper:2016,
    title = "Synchronization Emergence and its Effect on Performance in Queueing Systems ",
    journal = "Procedia CIRP",
    volume = "52",
    number = "",
    pages = "90 -- 95",
    year = "2016",
    note = "The Sixth International Conference on Changeable, Agile, Reconfigurable and Virtual Production (CARV2016) ",
    issn = "2212-8271",
    doi = "10.1016/j.procir.2016.07.016",
    url = "http://www.sciencedirect.com/science/article/pii/S2212827116307582",
    author = "Schipper, Manuel A. and Chankov, Stanislav M. and Bendul, Julia",
    keywords = "synchronization",
    keywords = "queueing theory",
    keywords = "production system",
    keywords = "manufacturing system design ",
    abstract = "Abstract Synchronization as a dynamic process has found applications in many fields. However, it remains unclear how this phenomenon relates to manufacturing systems. The aim of this study is to investigate the conditions for emergence of synchronization and its effects on the wide spectrum of production logistics performance objectives. Using queueing theory as the underlying methodology for deductive modeling of manufacturing systems, we run computer simulations on networks of queueing systems and investigate synchronization measurements in relation to system parameters and performance indicators. Our initial findings suggest that different types of manufacturing systems display different synchronization behaviors and that periodically driven systems with deterministic arrival and service rates display higher synchronization in comparison to stochastic ones. Further, we show that intrinsic physics synchronization is correlated to capacity utilization, throughput times and WIP levels, suggesting the co-activity of operations is related to highly utilized systems, while external physics synchronization is anticorrelated to throughput times and WIP levels, suggesting that higher efficiencies emerge with workstation repetitive behavior."
    }
 Dr. Chankov
Synchronization in Assembly Line – Data Analysis on a Car Mixed-Model Assembly Line
Synchronization in a broader sense means aligning a certain behavior or state over time. In the physical world, two systems can spontaneously synchronize with respect to each other even if there are only small physical interactions. Up to now it is not fully understood how synchronization affects assembly lines: Does a spontaneous synchronization also occur in mixed-model assembly lines? If so, what triggers it and how does it influence the achievement of the logistics objectives and the robustness of the processes?The purpose of this thesis is to study synchronization phenomena present in automotive assembly lines. Confidential data from a car manufacturer is used in order to understand what kind of synchronization phenomena emerge in mixed-model assembly lines. By applying synchronization measures to the data, the thesis will firstly examine the common assumption that assembly lines are synchronized and then derive implications for future research. A good starting point is: 

  • [DOI] S. M. Chankov, M. Hütt, and J. Bendul, “Synchronization in manufacturing systems: quantification and relation to logistics performance,” International journal of production research, 2016.
    [Bibtex]
    @article{Chankov2016a,
    author = {Chankov, Stanislav M. and H{\"u}tt, Marc-Thorsten and Bendul, Julia},
    title = {Synchronization in manufacturing systems: quantification and relation to logistics performance},
    journal = {International Journal of Production Research},
    doi = {10.1080/00207543.2016.1165876},
    URL = {http://dx.doi.org/10.1080/00207543.2016.1165876},
    eprint = {http://dx.doi.org/10.1080/00207543.2016.1165876},
    year={2016},
    abstract = {The term 'synchronization' in manufacturing refers to the provision of the right components to the subsequent production steps at the right moment in time. It is widely assumed that synchronization is beneficial to the logistics performance of manufacturing systems. However, it has been shown that synchronization phenomena can be detrimental to systems in which they emerge. To study if synchronization phenomena also occur in and affect manufacturing systems' performance, a formal quantification and holistic understanding of the types of synchronization phenomena emerging in manufacturing are needed. This article aims to fill this research gap by developing synchronization measures for manufacturing systems, applying these measures to real-world production feedback data and utilising them to test the assumption about synchronization's beneficial effect on logistics performance. We identify two distinct synchronization types occurring in manufacturing systems, logistics and physics synchronization, and show that they are negatively correlated. Further, we show that logistics synchronization and due date performance exhibit anti-correlation and thus question the assumption that synchronization leads to higher efficiency in manufacturing systems. This article aids production managers in designing and optimising production systems, and supports further empirical research in production planning and control and production system design.},
    }
  • [DOI] S. M. Chankov, G. Malloy, and J. Bendul, “The influence of manufacturing system characteristics on the emergence of logistics synchronization: a simulation study,” in Dynamics in logistics: proceedings of the 5th international conference ldic, 2016 bremen, germany, M. Freitag, H. Kotzab, and J. Pannek, Eds., Cham: Springer International Publishing, 2016, pp. 29-40.
    [Bibtex]
    @inbook{Chankov2016b,
    author="Chankov, Stanislav M. and Malloy, Giovanni and Bendul, Julia",
    editor="Freitag, Michael and Kotzab, Herbert and Pannek, J{\"u}rgen",
    title="The Influence of Manufacturing System Characteristics on the Emergence of Logistics Synchronization: A Simulation Study",
    bookTitle="Dynamics in Logistics: Proceedings of the 5th International Conference LDIC, 2016 Bremen, Germany",
    year="2016",
    publisher="Springer International Publishing",
    address="Cham",
    pages="29--40",
    isbn="978-3-319-45117-6",
    doi="10.1007/978-3-319-45117-6_3",
    url="http://dx.doi.org/10.1007/978-3-319-45117-6_3"
    abstract="The term 'synchronization' in manufacturing refers to the provision of the right components to the subsequent production steps at the right moment in time. It is still unclear how manufacturing system characteristics impact synchronization. Thus, the purpose of this paper is to investigate the effect of manufacturing systems' characteristics on the emergence of logistics synchronization in them. We conduct a discrete-event simulation study to examine the effect of three system characteristics: (1) material flow network architecture, (2) work content variation, and (3) order arrival pattern. Our findings suggest that the material flow network architecture and the work content variation are related to logistics synchronization. Linear manufacturing systems with stable processing times such as flow shops operate at high logistics synchronization levels, while highly connected systems with high variability of processing times such as job shops exhibit lower synchronization levels."
    }
  • [DOI] M. A. Schipper, S. M. Chankov, and J. Bendul, “Synchronization emergence and its effect on performance in queueing systems,” Procedia cirp, vol. 52, pp. 90-95, 2016.
    [Bibtex]
    @article{Schipper:2016,
    title = "Synchronization Emergence and its Effect on Performance in Queueing Systems ",
    journal = "Procedia CIRP",
    volume = "52",
    number = "",
    pages = "90 -- 95",
    year = "2016",
    note = "The Sixth International Conference on Changeable, Agile, Reconfigurable and Virtual Production (CARV2016) ",
    issn = "2212-8271",
    doi = "10.1016/j.procir.2016.07.016",
    url = "http://www.sciencedirect.com/science/article/pii/S2212827116307582",
    author = "Schipper, Manuel A. and Chankov, Stanislav M. and Bendul, Julia",
    keywords = "synchronization",
    keywords = "queueing theory",
    keywords = "production system",
    keywords = "manufacturing system design ",
    abstract = "Abstract Synchronization as a dynamic process has found applications in many fields. However, it remains unclear how this phenomenon relates to manufacturing systems. The aim of this study is to investigate the conditions for emergence of synchronization and its effects on the wide spectrum of production logistics performance objectives. Using queueing theory as the underlying methodology for deductive modeling of manufacturing systems, we run computer simulations on networks of queueing systems and investigate synchronization measurements in relation to system parameters and performance indicators. Our initial findings suggest that different types of manufacturing systems display different synchronization behaviors and that periodically driven systems with deterministic arrival and service rates display higher synchronization in comparison to stochastic ones. Further, we show that intrinsic physics synchronization is correlated to capacity utilization, throughput times and WIP levels, suggesting the co-activity of operations is related to highly utilized systems, while external physics synchronization is anticorrelated to throughput times and WIP levels, suggesting that higher efficiencies emerge with workstation repetitive behavior."
    }
  Dr. Chankov

Bachelor or Master Topics supervised by Prof. Uygun

Pitfalls of Just-in-Time Manufacturing Prof. Uygun
Improving Cocoa Supply Chains – A System Dynamics Approach Prof. Uygun
Calculation Methods for Milkruns in Lean Manufacturing Systems Prof. Uygun
Winners & Losers in Industry 4.0 – A Comparative Analysis of Emerging and Dying Industries Prof. Uygun
Problems with Supplier Kanban Prof. Uygun
Measuring the Industry 4.0 Maturity Level of Manufacturing Companies Prof. Uygun
Costs and Benefits of Implementing Industry 4.0 Technologies Prof. Uygun
Efficient Lot Sizes in Lean Manufacturing Systems Prof. Uygun
Do Supermarkets in Lean Manufacturing Systems Always Lower Inventory? A Linear Regression Analysis Prof. Uygun
Proper Intervals for Productive Maintenance Prof. Uygun
Costs of Quality – A Comprehensive Calculation Method Prof. Uygun
Capacity Adjustment: Decision Support Model Prof. Uygun
Characteristics of the Workforce in the Era of Industry 4.0 Prof. Uygun
Evaluation of Scheduling Algorithms for Steel Manufacturing Prof. Uygun
Effects of Network Structure on Inventory – A Comparative Analysis of Automotive and Cosmetics Industries Prof. Uygun

 Bachelor or Master Topics supervised by Prof. Wicaksono

Product Lifecycle Information Model for Reference Architectural Model Industrie 4.0 (RAMI 4.0)
RAMI 4.0 is the reference architectural model for industry 4.0 which standardize the approach to address issues related to industry 4.0 in a structured manner. One of those dimensions is the IT which is divided into six layers, i.e. asset, integration, communication, information, functional, and business. The information layer represents the data model and access to the assets. The data model has to be consistent during the whole product lifecycle. This thesis aims to answer the following research questions:

  • What are the example of typical industry 4.0 uses cases and how those use cases are addressed with RAMI 4.0 components?
  • Which objects are relevant for those typical use cases of industry 4.0 and are necessary to be modeled?
  • What kind of representation technology is the most appropriate, e.g. XML, linked data (RDF)

This thesis consists of the following works:

  • Analysis of related fundamental theories of RAMI 4.0 and product lifecycle management
  • Identification of typical use cases in industry 4.0
  • Evaluation of existing information modelling technologies
  • Generic information modelling
  • Validation through the identified use cases
  • Documentation and presentation
Prof. Wicaksono
Enabling Multilevel and Holistic Production Management System to Improve Energy and Resource flexibility in Industry 4.0

Currently, companies develop measures to improve energy and resource flexibility and efficiency in individual and local manners and also in a certain scope. The measures often fail to achieve both flexibility and efficiency because the developed measures of energy/resource efficiency might give negative impact to the energy/resource flexibility and vice-versa. This issue is due to the lack of a holistic view of the various production chain stakeholders, and neglect the analysis of the underlying interactions at an ecosystem, business, factory, and process level. Therefore, this thesis aims to answer the following questions:

  • Which processes and ecosystem components have to be considered to develop measures to improve both energy/resource flexibility and efficiency?
  • What kind of information modelling technologies enable a holistic view of a production management system to improve the measure development?
  • Which objects should be modeled?

This thesis consists of the following works:

  • Analysis of related fundamental theories of energy/resource flexibility and efficiency in production
  • Identification of processes and ecosystem components in production management
  • Evaluation of existing information modelling technologies
  • Information modelling which enables the multilevel and holistic view of production management
  • Validation through use cases
  • Documentation and presentation
Prof. Wicaksono
A Systematic Comparison of Information Modelling Approaches in Building Lifecycle Management and Product Lifecycle Management

Both buildings and products have to be managed along their life cycle in order to take the maximum benefits from them. Information technology tools are required to improve the processes across the stages of their lifecycle. Those tools generate and consume data across lifecycle stages. Data generated by a tool in a certain stage can usually not be consumed by other tools in other stages. This is due to the lack of a consistent information model across lifecycle. Researchers have developed approaches to address the issue in both product and building domains. This thesis aims to compare different approaches systematically covering the following criteria:

  • The lifecycle stages
  • The typical stakeholders of each stage
  • The typical processes of each stage
  • The typical tools of each stage
  • The Information modelling technologies which represent the consistent information model across stages
Prof. Wicaksono

Bachelor or Master Topics supervised by Prof. Hütt

Prof. Hütt (Professor of Systems Biology at Jacobs University) has agreed to supervise the following thesis topics. Please approach him directly in case of any questions.

Time constants of biological enzymes as machine capacities
Metabolism is a production process in biological cells, where enzymes (the ‘machines’) convert chemical compounds (metabolites) into other chemical compounds, leading to an intricate network of interacting machines. The striking parallel between metabolism and industrial production systems offers the fascinating possibility to compare evolved and designed systems. As ever more information on metabolic systems becomes electronically available in bioinformatics databases, this parallel can now be quantitatively explored. The goal of the project is to use production planning algorithms for machine capacities, apply them to a metabolic network and see, whether the actual capacities (given by the inverse time constants of enzymes and available via databases) match those predictions.Further reading:
Beber, M. E. and Hütt, M. (2012). How do production systems in biological cells maintain their function in changing environments? Logistics Research, 5(3-4):79–87.
Prof. Hütt
Product diversity and network structure: a minimal model

A comparatively unexplored aspect of manufacturing is the relationship between the production network and the diversity of the manufactured products. Previous work on evolved flow networks (Beber et al. 2013) has shown that the network architecture is strongly affected by the complexity of the network’s required ‘output pattern’. In a series of small investigation we want to understand this phenomenon more deeply and apply the findings to manufacturing.
The goal of the project component described here is to formulate heuristics for generating a production network for a given product structure using path combinatorics. Then the network architectures will be statistically analyzed in order to establish relationships between product diversity and network structure.

Further reading:
Beber, M., Armbruster, D. and Hütt, M.-Th. (2013) The prescribed output pattern regulates the modular structure of flow networks. European Physical Journal B 86, 473. DOI: 10.1140/epjb/e2013-40672-3.

Prof. Hütt
Product diversity and network structure: analysis of evolved flow networks

A comparatively unexplored aspect of manufacturing is the relationship between the production network and the diversity of the manufactured products. Previous work on evolved flow networks (Beber et al. 2013) has shown that the network architecture is strongly affected by the complexity of the network’s required ‘output pattern’. In a series of small investigation, we want to understand this phenomenon more deeply and apply the findings to manufacturing.
The goal of the project component described here is to analyze the database from Beber et al. (2013) from the perspective of novel network properties: linearity, path combinatorics and betweenness centrality.

Further reading:
Beber, M., Armbruster, D. and Hütt, M.-Th. (2013) The prescribed output pattern regulates the modular structure of flow networks. European Physical Journal B 86, 473.

Prof. Hütt
Product diversity and network structure: analysis of real production networks

A comparatively unexplored aspect of manufacturing is the relationship between the production network and the diversity of the manufactured products. Previous work on evolved flow networks (Beber et al. 2013) has shown that the network architecture is strongly affected by the complexity of the network’s required ‘output pattern’. In a series of small investigation we want to understand this phenomenon more deeply and apply the findings to manufacturing.
The goal of the project component described here is to study, whether similar relationships are also observed in real manufacturing systems. To this end, product diversity will be analyzed and then statistically compared with the system’s material flow networks.

Further reading:
Beber, M., Armbruster, D. and Hütt, M.-Th. (2013) The prescribed output pattern regulates the modular structure of flow networks. European Physical Journal B 86, 473.

Prof. Hütt
Synchronization as a quantifier of activity patterns: delay avalanches

The various concepts of synchronization attempt to capture the pattern of activity in a production network. It has been established before that high synchronization can lead to system-wide failures and thus reduce the robustness of the system against perturbations (Fretter et al. 2010). This project uses the general model paradigm of ‘avalanches on graphs’ to study this phenomenon further: How does the network architecture facilitate such avalanches? Can we adapt standard avalanche models to account for lateness propagation in production systems?

Further reading:
Fretter, C., Krumov, L., Weihe, K., Müller-Hannemann, M. and Hütt, M.-Th. (2010) Phase synchronization in railway timetables, European Physical Journal B 77, 281-289.

Prof. Hütt
Synchronization as a quantifier of activity patterns: activity as excitable dynamics

The various concepts of synchronization attempt to capture the pattern of activity in a production network. It has been established before that high synchronization can lead to system-wide failures and thus reduce the robustness of the system against perturbations (Fretter et al. 2010). This project asks, how different types of synchronization (termed logistics synchronization and physics synchronization in Chankov et al. 2015) quantify activity patterns in a graph, and thus ‘calibrate’ these measures. In order to understand the generic properties of these synchronization measures, we will use a simple model of activity, namely excitable dynamics on graphs (see, e.g., Müller-Linow et al. 2008) to simulate activity patterns and then analyze the synchronization measures as a function of network architecture and parameters of the dynamics.

Further reading:
Fretter, C., Krumov, L., Weihe, K., Müller-Hannemann, M. and Hütt, M.-Th. (2010) Phase synchronization in railway timetables, European Physical Journal B 77, 281-289.
Chankov, S., Bendul, J. and Hütt, M.-Th. (2015) Synchronization in Manufacturing Systems: Quantification and Relation to Logistics Performance. International Journal of Production Research, under review.
Müller-Linow, M., Hilgetag, C. and Hütt, M.-Th. (2008) Organization of excitable dynamics in hierarchical biological networks. PLoS Computational Biology 4, e1000190.

Prof. Hütt
Sequentiality and linearity of production networks

Important properties of manufacturing processes are determined by the combinatorics of paths in the material flow network (see Garcia et al. 2014 for an example, how such a question is investigated for closed paths). Deterministic linear sequences in this material flow ‘decouple’ parts of the system from other parts. The amount of linearity in a production network is therefore an important architectural quantity. While there is no standard way of measuring the linearity of a network, a rich set of network quantifiers has emerged over the last years addressing aspects of this question. The purpose of this project is to perform a literature review of these quantifiers and then compare them using a small set of reference networks with varying amounts of linearity.

Further reading:
Garcia, G.C., Lesne, A., Hilgetag C.C. and Hütt, M.-Th. (2014) The role of topological cycles in excitable dynamics on graphs. Phys. Rev. E 90, 052805.

Prof. Hütt
The graph chromatic number as a robustness indicator of production networks

The graph coloring problem (distribute colors from a list on a graph such that no same colors are linked) is related to many scheduling problems in logistics. Attempting to distribute the colors based on local decisions only generates coloring dynamics, which are a minimal model of autonomous control (see, e.g., Windt and Hütt 2010). Given a graph, the minimal number of colors for which the graph coloring problem can be solved is called the ‘chromatic number’ of the graph. Qualitatively speaking, this quantity determines, how easy scheduling is on the graph. We can expect that logistics performance of, e.g., a production network will depend strongly on this chromatic number. Using numerical experiments with scheduling software this relationship will be explored.Further reading:
Windt, K. and Hütt, M.-Th. (2010) Graph Coloring Dynamics: A Simple Model Scenario for Distributed Decisions in Logistics. CIRP Annals Manufacturing Technology 59, 461-464.
Prof. Hütt
Network recovery: a literature review with small numerical experiments

How networks recover from perturbations is a general question with deep implications for logistics systems. As an example, in Hao et al. (2015) the performance of a distributed insurance system under spatially and temporally correlated failures has been studied. The goal of this project is to understand, how the recovery of (production or distribution) networks is influenced by their architecture. The starting point will be a literature review of attempts to quantify and analyze network recovery. This survey of theoretical studies will be complemented by own numerical experiments on network recovery.

Further reading:
Hao, Y., Armbruster, D. and Hütt, M.-Th. (2015) Node survival in networks under correlated attacks. PLoS One, in press.

Prof. Hütt
Network representations of production systems

Across many disciplines, the formal language of nodes and links provides an efficient data structure for representing complex systems. Such representations can help comparing diverse systems.  In the case of production systems, nodes can be machines, processes, inventories, products at intermediate stages of production, or check points. Links can represent material flow, regulation, control and decision alternatives.
As an example, in Becker et al. (2011) production systems are represented as networks of cyclically operating devices. In this way, a comparison with traffic networks and production systems in biological cells (metabolic networks) could be achieved.
The goal of this project is to review the different network representations of production systems and analyze, how these network representations can help understand the functioning of these systems.

Further reading:
Becker, T., Beber, M.E., Windt, K., Hütt, M.-Th. and Helbing, D. (2011) Flow control by periodic devices: A unifying language for the description of traffic, production, and metabolic systems. J. Stat. Mech, P05004.

Prof. Hütt
Production networks vs. information processing networks

Across many disciplines, the formal language of nodes and links provides an efficient data structure for representing complex systems. Such representations can help comparing diverse systems.
Such networks tend to fall into two classes: production networks, characterized by their material flow, and information processing networks, characterized by their flow of information.
The goal of this project is a high-level comparison of these two classes of networks: What are the main functional differences (e.g., conservation laws)? Do they differ systematically in their architectures? How do the functional requirements differ for these networks? What do efficiency and robustness mean in each class?

Prof. Hütt
Random walks as a reference model for material flows

Understanding the material flow in manufacturing systems and its impact on logistics performance indicators is one of the principal goals production logistics. In many complex systems, a proper analysis of available data is only possible when contrasted to suitable versions of random data. Here, a simple model for random material flows, based on random walks, will be explored. Over the last decade, random walks on graphs have dramatically enhanced our understanding of the scaling of fluctuations in networks (see, e.g., Kosmidis et al. 2015). The goal of this project is to introduce modifications to a standard random walk (like a preference to move from an input layer to an output layer of the network) and study, how well the random walk reproduces statistical features of real material flows in manufacturing.

Further reading:
Kosmidis, K., Beber, M. and Hütt, M.-Th. (2015) Network heterogeneity and node capacity lead to heterogeneous scaling of fluctuations in random walks on graphs. Advances in Complex Systems 18, 1550007.

Prof. Hütt
Scaling laws in production logistics

Scaling relationships are among the most surprising findings about complex social and technological systems: laws allowing to predict with high accuracy the number of patents, crimes and restaurants just from the population size (see Bettencourt and West 2010); laws relating the number of machines to the number of regulators in production systems in biological cells (Maslov et al. 2009). The goal of this project is the search for such scaling laws in production systems. The starting point will be a survey of publically available databases about company sizes and infrastructures.

Further reading:

Bettencourt, L, and Geoffrey West, G.B. (2010) A unified theory of urban living. Nature 467, 912-913.

Maslov, S., Krishna, S., Pang, T. and Sneppen, K. (2009) Toolbox model of evolution of prokaryotic metabolic networks and their regulation. PNAS 106, 9743.

 Prof. Hütt