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This study aims to investigate the suitability of a multi-step prototyping strategy for producing pneumatic rotary vane actuators (RVAs) for the development of lightweight robots and actuation systems.

RVAs typically have cast aluminum housings and injection-molded seals that consist of hard thermoplastic cores and soft elastomeric overmolds. Using a combination of additive manufacturing (AM), computer numerical control (CNC) machining and elastomer molding, a conventionally manufactured standard RVA was replicated. The standard housing design was modified, and polymeric replicas were obtained by selective laser sintering (SLS) or PolyJet (PJ) printing and subsequent CNC milling. Using laser-sintered molds, actuator seals were replicated by overmolding laser-sintered polyamide cores with silicone (SIL) and polyurethane (PU) elastomers. The replica RVAs were subjected to a series of leakage, friction and durability experiments.

The AM-based prototyping strategy described is suitable for producing functional and reliable RVAs for research and product development. In a representative durability experiment, the RVAs in this study endured between 40,000 and 1,000,000 load cycles. Frictional torques were around 0.5 Nm, which is 10% of the theoretical torque at 6 bar and comparable to that of the standard RVA. Models and parameters are provided for describing the velocity-dependent frictional torque. Leakage experiments at 10,000 load cycles and 6 bar differential pressure showed that PJ housings exhibit lower leakage values (6.8 L/min) than laser-sintered housings (15.2 L/min), and PU seals exhibit lower values (8.0 l/min) than SIL seals (14.0 L/min). Combining PU seals with PJ housings led to an initial leakage of 0.4 L/min, which increased to only 1.2 L/min after 10,000 load cycles. Overall, the PU material used was more difficult to process but also more abrasion- and tear-resistant than the SIL elastomer.

More work is needed to understand individual cause–effect relationships between specific design features and system behavior.

To date, pneumatic RVAs have been manufactured by large-scale production technologies. The absence of suitable prototyping strategies has limited the available range to fixed sizes and has thus complicated the use of RVAs in research and product development. This paper proves that functional pneumatic RVAs can be produced by using more accessible manufacturing technologies and provides the tools for prototyping of application-specific RVAs.

Paul Samuelson was attracted to the irregular economic development pattern of some South American countries because of the links between economic performance and political factors. He discussed the influence of “populist democracy” on Argentina’s relative economic stagnation, which, he argued in the 1970s and early 1980s, served as a dangerous paradigm for the American economy under stagflation. Stagflation phenomena marked the end of Samuelson’s “neoclassical synthesis.” Moreover, he applied his concept of “capitalist fascism” to deal with military dictatorships in Brazil and (especially) in Chile. The Brazilian translation of his Economics in 1973 brought about a correspondence with Brazilian economists about the “fascist” features of the regime. The main variable behind the South American economic and politically unstable processes discussed by Samuelson was economic inequality, which became also a conspicuous feature of the American economy since the adoption of market-based policies in the 1980s and after.

Deutsche Bahn AG (Deutsche Bahn hereafter) was the former German railroad monopolist until deregulation in 1996. It was a well-known company that operated in worldwide markets for transport and logistics at the time of the case (late 2013). The case “Deutsche Bahn AG: a former monopoly off track?” focuses on the opportunities and challenges faced by Deutsche Bahn with regard to its position in the German individual transportation market. On the one hand, Deutsche Bahn is facing external problems. Increasing competition in short- and long-distance traffic threatens its strong business position. The competition emerged from a growing long-distance bus market and the increase in private railway companies. During the last few years before 2013, Deutsche Bahn has lost several public tenders for individual passenger travel in Germany. On the other hand, Deutsche Bahn has internal problems that endanger its image as a service company. A lack of service quality and the technical condition of its trains has led to rising numbers of customer complaints. In addition, staffing and punctuality problems have exacerbated the situation. One of the main technical issues the company faces is that ordered trains have not been delivered on time. Given the focus on Deutsche Bahn’s domestic challenges, its international business activities are tackled only briefly. While regulatory and political events have an impact on Deutsche Bahn, these are not the main subjects of the case.

This case has been written from public sources. Consequently, no company release is provided. None of the information has been disguised in any way.

The case is intended for use in a 90-minute strategic management class attended by students at the end of their undergraduate studies or in postgraduate study. Although the case relates to issues in strategic management, the special regulatory environment and some of the issues covered could make the case a useful complement in other classes as well, such as classes in supply chain management (procurement) or the management of public companies. Therefore, students should have basic knowledge in developing strategies, management, marketing, human resource management, and finance.

Strategic Analysis and Strategic Management, Railroad Logistics, Deregulation of a former Monopoly, Stakeholder Theory.

Improving the use of annotations in lecture recordings.

Requirements analysis with scenario based design (SBD) on focus groups.

These seven points have been extracted from the feedback of the focus groups: (1) Control of the annotation feature (turn on/turn off). (2) An option to decide who is able to see their comments (groups, lecturer, friends). (3) An easy and paper-like experience in creating a comment. (4) An option to discuss comments. (5) An option to import already existing comments. (6) Color-coding of the different types of comments. (7) An option to print their annotations within the context of the recording.

The study was performed to improve the open-source lecture recording system Opencast Matterhorn.

Annotations can help to enable the students that use lecture recordings to move from a passive watching to an active viewing and reflecting.