Supply chain design for industrial additive manufacturing

in International Journal of Operations and Production Management (2022)

Supply characteristics and membership choice in round-trip and free-floating carsharing systems

Scientific Conference (2019, June)

The Supply of Hours Worked and Endogenous Growth Cycles

E-print/Working paper (2020)

We show that declining hours of work per worker in conjunction with a growing work force may give rise to growth cycles. This is accomplished in an overlapping generations model where individuals are ... [more ▼]

We show that declining hours of work per worker in conjunction with a growing work force may give rise to growth cycles. This is accomplished in an overlapping generations model where individuals are endowed with Boppart-Krusell preferences (Boppart and Krusell (2020)), i. e., the wage elasticity of their supply of hours worked is negative. On the supply side, economic growth is due to the expansion of consumption-good varieties through endogenous research. We show that a sufficiently negative equilibrium elasticity of the individual supply of hours worked to an expansion in the set of consumption-good varieties opens up the possibility of growth cycles where the economy fluctuates between two regimes, one with and the other without an active research sector. We identify period-2 and period-3 cycles, conclude with Li and Yorke (1975) that cycles of any periodicity exists, and generalize our findings to period-n cycles. We show that the possibility of cycles occurs under empirically plausible conditions. Throughout, we emphasize that the economics of cycles is linked to the intergenerational trade of shares and their pricing in the asset market. [less ▲]

The supply of hours worked and fluctuations between growth regimes

in Journal of Economic Theory (2021)

Declining hours of work per worker in conjunction with a growing work force may give rise to fluctuations between growth regimes. This is shown in an overlapping generations model with two-period lived ... [more ▼]

Declining hours of work per worker in conjunction with a growing work force may give rise to fluctuations between growth regimes. This is shown in an overlapping generations model with two-period lived individuals endowed with Boppart-Krusell preferences (Boppart and Krusell (2020)). On the supply side, economic growth is due to the expansion of consumption-good varieties through endogenous research. A sufficiently negative equilibrium elasticity of the individual supply of hours worked to an expansion in the set of consumption-good varieties destabilizes the steady state so that equilibrium trajectories may fluctuate between two growth regimes, one with and the other without an active research sector. Fluctuations affect intergenerational welfare, the evolution of GDP, and the functional income distribution. A stabilization policy can shift the economy onto its steady-state path. Fluctuations arise for empirically reasonable parameter constellations. The economics of fluctuations between growth regimes is linked to the intergenerational trade of shares and their pricing in the asset market. [less ▲]

Support in Abstract Argumentation

in Proceedings of the Third International Conference on Computational Models of Argument (COMMA'10) (2010)

n this paper, we consider two drawbacks of Cayrol and Lagasque-Schiex's meta-argumentation theory to model bipolar argumentation frameworks. We consider first the “lost of admissibility” in Dung's sense ... [more ▼]

n this paper, we consider two drawbacks of Cayrol and Lagasque-Schiex's meta-argumentation theory to model bipolar argumentation frameworks. We consider first the “lost of admissibility” in Dung's sense and second, the definition of notions of attack in the context of a support relation. We show how to prevent these drawbacks by introducing support meta-arguments. Like the model of Cayrol and Lagasque-Schiex, our formalization confirms the use of meta-argumentation to reuse Dung's properties. We do not take a stance towards the usefulness of a support relation among arguments, though we show that if one would like to introduce them, it can be done without extending Dung's theory. Finally, we show how to use meta-argumentation to instantiate an argumentation framework to represent defeasible support. In this model of support, the support relation itself can be attacked. [less ▲]

Support of communication and cooperation in the asylum process with the help of blockchain: A feasibility study by the Federal Office for Migration and Refugees

Report (2018)

Digital technologies are changing our society in many ways. In addition to significant increases in productivity and new forms of value creation, the rapid digital change also brings with it a multitude ... [more ▼]

Digital technologies are changing our society in many ways. In addition to significant increases in productivity and new forms of value creation, the rapid digital change also brings with it a multitude of political and social challenges. While the digitization of the public sector in Germany is still facing challenges, other countries are already further. For example, Estonia has already largely digitized its administration. The federal government would also like to advance Germany with a targeted digitization strategy and strengthen public administration through the use of digital technologies. One of the focus technologies in this context is blockchain. Blockchain is a decentralized data structure, in which data in cryptographically linked blocks can be stored invariably and traceably. The essential concept of blockchain technology is to manage the data to be stored through a subscriber network instead of a central instance. In addition, new blockchain technologies make it possible to automate parts of the cross-agency process management. Due to its properties, blockchain technology offers a good opportunity for coordination in federal structures, as required by the German asylum process. In addition to one body primarily responsible, the Federal Office for Migration and Refugees, other authorities at both federal and state level are involved in the asylum process. For example, initial reception centers and immigration authorities are subordinate to the respective federal states or part of the local government. This results in a large number of process variants, heterogeneous IT infrastructures and an incomplete digital exchange of information. A cross-agency data source already exists in the form of the Central Register of Foreigners (AZR). The AZR contains a large amount of data that may be recorded and stored by the authorized authorities in accordance with applicable law (especially AZRG). In addition, there is a need for IT-based support for cross-agency communication and cooperation. The Federal Office for Migration and Refugees has now evaluated to what extent blockchain can contribute to overcoming these challenges and promote the establishment of digital identities in the asylum context as well as cross-agency communication and cooperation. A proof-of-concept project that the Federal Office carried out in the first half of 2018 serves as an essential reference point. The project began with the selection of the use case ("simplified asylum process") and a pre-evaluation of the suitability of the blockchain technology. After a positive pre-evaluation, a suitable system was developed by a mixed team from the Federal Office, the Fraunhofer FIT Business Informatics project group and a technology partner. The project was then evaluated according to a blockchain-specific evaluation framework. In addition to technical and professional aspects, the focus here was in particular on issues relating to data protection law. The proof-of-concept project has shown that the use of blockchain technology could support cross-agency communication and cooperation in the asylum process. In addition, blockchain could lay an important foundation for the establishment of digital identities and make the process flow of an asylum seeker traceable on the basis of such an identity. It is true that it has not yet been possible to fully implement all applicable data protection regulations in the developed proof-of-concept. However, the knowledge gained in the course of the project forms a promising basis for the development of a data protection-compliant blockchain-based solution for the asylum process. In addition, due to the federal structure taken into account, the developed concept could also be scaled beyond Germany's borders. A blockchain-based, transnational management of asylum processes could thus become a joint project of the European member states to strengthen cooperation while preserving federal structures. Blockchain technology could thus be the beginning of digital federalism in Europe (also in the asylum area). [less ▲]

A support theorem for the filter under infinite dimensional noise and unbounded observation coefficient

in Applied Mathematics & Optimization (1999), 39

In this paper we consider a nonlinear filtering problem with an unbounded observation coefficient, correlated noises, and a signal process driven by an infinite dimensional Brownian motion. We prove that ... [more ▼]

In this paper we consider a nonlinear filtering problem with an unbounded observation coefficient, correlated noises, and a signal process driven by an infinite dimensional Brownian motion. We prove that the unnormalized filter admits a smooth density which is in the Schwartz space and we give a description of the support of the law of this density. [less ▲]

Supporting bariatric surgery patients in their aftercare journey: a playful technological intervention “Truth-or-Dare?"

Scientific Conference (2021, June)

Background The amount of people coping with obesity keeps on increasing. While the physical comorbidities are clearly visible, mental issues such as a low self-image are just as damaging. Bariatric ... [more ▼]

Background The amount of people coping with obesity keeps on increasing. While the physical comorbidities are clearly visible, mental issues such as a low self-image are just as damaging. Bariatric surgery is currently the most effective treatment with long-term results [2, 3]. Its effectiveness is however often expressed in postoperative weight loss, leaving the impact on psychological health aside [3]. Methods To support bariatric patients in the aftercare pathway, we designed Truth-or-Dare. Combining a physical artefact and a mobile app, Truth-or-Dare is a playful way to track patients' mental state, using challenges to help them to establish a better self-image and a physical exercise routine. The frame attracts attention by dropping magnetic wooden blocks, indicating it is time to play! The app displays a personalized exercise or reflection challenge. By placing the block back on one side of the frame the choice is made: truth or dare? The Truth-or-Dare frame and app have been used by a former bariatric patient for two weeks. Every 6-12 hours a block fell out of the frame. We conducted two semistructured interviews, the first focused on the experience and initial thoughts about the product, the second informed by the data gathered. During the deployment, we also implemented a feedback loop to collect participants’ experiences with the challenges, allowing to understand which strategy was the most effective for a patient and to iterate on them. Findings The challenges were positively perceived by the participant and helped her to become more aware of her behavior and mindset. While she enjoyed taking her time to perform each challenge, she felt pressed and rushed by the too short interval between challenges. She often rated the challenges as unpleasant, complicated or annoying, yet motivating. If a challenge is annoying, it does not mean it is not motivating. “If I would not want challenges like that, I would ignore my problems.” We observed a pattern of switching between truth and dare challenges, mainly triggered by the physical properties of the board. Discussion Playful Truth-or-Dare challenges implemented in a physical artefact and a related app are a new intervention approach for mental wellbeing after bariatric surgery. It shows potential in raising awareness amongst patients around their behaviors and motivating them throughout their journey. As the product is placed in a shared environment, family members are encouraged to join, which has a positive influence on both the patient and partner [1]. The design of the physical product uses friction as a motivational mechanism: (a) a block on the ground calls for action. Will the patient remove it without performing a challenge or engage with the game? (b) placing the block back, one can choose Truth or Dare. Yet, the board is designed to prevent one type of challenge to be chosen too often. These moments of friction act as triggers to step outside the comfort zone. Further research is necessary to refine the challenges, or even personalize them, and to investigate the longterm effect of Truth-or-Dare on patients’ mental wellbeing and self-image. [less ▲]

Supporting Change in Product Lines Within the Context of Use Case-driven Development and Testing

Doctoral thesis (2019)

Product Line Engineering (PLE) is a crucial practice in many software development environments where systems are complex and developed for multiple customers with varying needs. At the same time, many ... [more ▼]

Product Line Engineering (PLE) is a crucial practice in many software development environments where systems are complex and developed for multiple customers with varying needs. At the same time, many business contexts are use case-driven where use cases are the main artifacts driving requirements elicitation and many other development activities. In these contexts, variability information is often not explicitly represented, which leads to ad-hoc change management for use cases, domain models and test cases in product families. In this thesis, we address the problems of modeling variability in requirements with additional traceability to feature models and the manual and error prone requirements configuration and regression testing in product families. We provide the following contributions: - A modeling method for capturing variability information in product line use case and domain models by relying exclusively on commonly used artifacts in use-case driven development, thus avoiding unnecessary modeling overhead. - An approach for automated configuration of product specific use case and domain models that guides customers in making configuration decisions and automatically generates use case diagrams, use case specifications, and domain models for configured products. - A change impact analysis approach for evolving configuration decisions in product line use case models that automatically identifies the impact of decision changes on other decisions, and incrementally reconfigures product specific use case diagrams and specifications for evolving decisions. - An approach for automated classification and prioritization of system test cases in a family of products that automatically classifies and prioritizes, for each new product, system test cases of previous product(s) in a product line, and provides guidance in modifying existing system test cases to cover new use case scenarios that have not been tested in the product line before. All our approaches have been developed and evaluated in close collaboration with our industry partner IEE. [less ▲]

SUPPORTING COLLABORATIVE LEARNING INSIDE COMMUNITIES OF PRACTICE THROUGH PROACTIVE COMPUTING

in Proceedings of the 5th annual International Conference on Education and New Learning Technologies, Barcelona, Spain 1-3 July, 2013 (2013)

This work focuses on a particular area of Computer-Supported Collaborative Learning (CSCL) which looks at how to create, organize and develop Communities of Practice inside a Virtual Learning Management ... [more ▼]

This work focuses on a particular area of Computer-Supported Collaborative Learning (CSCL) which looks at how to create, organize and develop Communities of Practice inside a Virtual Learning Management System (VLMS), i.e. Moodle™, with the help of Proactive Computing. The goal is to increase the on-line participation of students, stimulate the learning process and address common issues in higher education institutions, like transportation, housing, health concerns and students social activities. To achieve this goal, we propose different ways of organizing students into virtual communities with a clear purpose and we provide the tools for building and sharing the knowledge, while our system informs, guides and assists students through the whole process. The current level of involvement of the students at our university’s local Moodle™ platform is quite low, despite the fact the students are obliged to use the platform for extracting, viewing and submitting assignments and other course-related materials. This is why we consider Moodle™ quite static and limited from the point of view of the interface and from the existing ways of creating learning communities. By employing Proactive Computing ([11]), the system becomes aware to the actions or lack of actions of its users, and, on the basis of predefined proactive scenarios, takes appropriate actions for steering users towards enhanced collaboration and social learning. Using the structure of the proactive rule defined in ([13]), we have developed a new set of proactive rules which aims to automatically initiate, maintain and expand social interactions inside communities of students. Each rule is part of one of the stages of the Proactive Cycle, the whole model of proactive scenarios meant to support collaborative techniques for sharing experience, news and practices. The Proactive Cycle is divided into three main categories: “Setting-up Social Groups”, “Enhancing Social Life” and “Adjusting the Social Groups”. Each community starts its life-cycle in the first category and then, after developing over a certain period of time, it will either become a significant community or the system will merge it with another group, or even ending its life-cycle if there are not so many members or the group is inactive. The set of rules will run on the Proactive Engine, developed by Zampunieris ([13]), and aside the local Moodle™ server at our university. A new Java Web Socket Server will ensure an encrypted real-time connection between the Proactive Engine and the Moodle™ blocks (parts of the user interface) developed specially for these experiments. These first series of experiments are taking into account around 1300 real students who currently use the Moodle™ platform over a full semester. We believe our study will be significant in terms of understanding the evolution of virtual study communities, for providing a better learning experience to the users, and in terms of integrating new technologies into an existing learning management system (LMS). The results of this study, which is deployed over the summer semester, are expected to emphasize the importance of having a dynamic, proactive and intuitive learning environment. The Proactive Engine is capable to be integrated with other LMS systems, which would help the whole learning community. [less ▲]