TY - RPRT A1 - Bohn, Dieter A1 - Funke, Harald A1 - Gier, J. A1 - Heuer, T. T1 - Untersuchung des Strömungsausgleichs in den Schaufelreihen ungleichförmig ungeströmter Turbomaschinen N2 - Abschlussbericht über das Vorhaben FVV-Nr. 665 (AIF-Nr. 10780). Laufzeit 01.08.1996 bis 31.10.1999. Heft R 504 (1999). S. 99-124. Informationstagung Turbinen, Herbst 1999, Heidelberg. KW - Strömungsmaschine KW - Turbine KW - Strömungsausgleich KW - Turbine Y1 - 1999 ER - TY - RPRT A1 - Bohn, Dieter A1 - Funke, Harald A1 - Heuer, T. T1 - Sonden-Schaufel-Interaktion bei stationären Messungen mit pneumatischen Strömungssonden in engen Axialspalten N2 - Abschlussbereicht über das Anschlussvorhaben zu FVV-Nr. 665 (AIF-Nr. 10780). Heft R 511 (2001). 23 S. Informationstagung Turbinen, Frühjahr 2001, Frankfurt. KW - Strömungsmaschine KW - Turbine KW - Strömungsausgleich KW - Turbine KW - Strömungssonde Y1 - 2001 ER - TY - JOUR A1 - Bohn, Dieter A1 - Funke, Harald A1 - Heuer, Tom A1 - Bütikofer, J. T1 - Numerical and experimental investigations of the influence of different swirl-ratios on the temperature streak equalization in a 4-stage turbine JF - ASME Turbo Expo 2000 ; Munich, May 8-11 2000 Y1 - 2000 N1 - ASME-paper ; 2000-GT-250 CY - Munich ER - TY - RPRT A1 - Bohn, Dieter A1 - Funke, Harald A1 - Sürken, N. T1 - Aerodynamische Entlastung der Schaufelspalte durch Konturierung des Meridiankanals [Zwischenbericht] N2 - Zwischenbericht über das Vorhaben FVV-Nr. 0666880. Laufzeit 01.03.1998 bis 31.03.2000. Heft R 507 (2000) . 19 S. Informationstagung Turbinen, Frühjahr 2000, Frankfurt am Main KW - Strömungsmaschine KW - Turbine KW - Spaltentlastung KW - Turbine Y1 - 2000 ER - TY - JOUR A1 - Bohn, Dieter A1 - Funke, Harald A1 - Sürken, Norbert A1 - Kreitmeier, F. T1 - Numerical and experimental investigations on endwall contouring in a four-stage turbine JF - ASME Turbo Expo Land Sea & Air 2001 : June 4 - 8, 2001, New Orleans, Louisiana / IGTI, International Gas Turbine Institute. American Society of Mechanical Engineers. International Gas Turbine Institute .. Y1 - 2001 SN - 0-7918-3528-6 N1 - ASME-Paper 2001-GT-0481 PB - ASME CY - New York, NY ER - TY - RPRT A1 - Bohn, Dieter A1 - Funke, Harald A1 - Wolff, M. A1 - Sürken, N. T1 - Aerodynamische Entlastung der Schaufelspalte durch Konturierung des Meridiankanals [Abschlussbericht] N2 - Abschlussbericht über das Vorhaben Nr. 688 (FVV-Nr. 066880). Laufzeit 01.04.2000 bis 31.03.2001. Heft R 516 (2002). 24 S. Informationstagung Turbinen, Frühjahr 2002, Frankfurt-Möhrfelden KW - Strömungsmaschine KW - Turbine KW - Spaltentlastung KW - Turbine Y1 - 2002 ER - TY - RPRT A1 - Bohn, Dieter A1 - Funke, Harald A1 - Wolff, M. A1 - Sürken, N. T1 - Aerodynamische Entlastung der Schaufelspalte durch Konturierung des Meridiankanals [Zwischenbericht] N2 - Zwischenbericht über das Vorhaben Nr. 688 (FVV-Nr. 066880). Laufzeit 01.04.2000 bis 31.03.2001. Heft R 514 (2001). 21 S. Informationstagung Turbinen, Herbst 2001, Dresden-Radebeul KW - Strömungsmaschine KW - Turbine KW - Spaltentlasung KW - Turbine Y1 - 2001 ER - TY - JOUR A1 - Bohndick, Carla A1 - Bosse, Elke A1 - Jänsch, Vanessa K. A1 - Barnat, Miriam T1 - How different diversity factors affect the perception of first-year requirements in higher education JF - Frontline Learning Research N2 - In the light of growing university entry rates, higher education institutions not only serve larger numbers of students, but also seek to meet first-year students’ ever more diverse needs. Yet to inform universities how to support the transition to higher education, research only offers limited insights. Current studies tend to either focus on the individual factors that affect student success or they highlight students’ social background and their educational biography in order to examine the achievement of selected, non-traditional groups of students. Both lines of research appear to lack integration and often fail to take organisational diversity into account, such as different types of higher education institutions or degree programmes. For a more comprehensive understanding of student diversity, the present study includes individual, social and organisational factors. To gain insights into their role for the transition to higher education, we examine how the different factors affect the students’ perception of the formal and informal requirements of the first year as more or less difficult to cope with. As the perceived requirements result from both the characteristics of the students and the institutional context, they allow to investigate transition at the interface of the micro and the meso level of higher education. Latent profile analyses revealed that there are no profiles with complex patterns of perception of the first-year requirements, but the identified groups rather differ in the overall level of perceived challenges. Moreover, SEM indicates that the differences in the perception largely depend on the individual factors self-efficacy and volition. Y1 - 2021 U6 - https://doi.org/10.14786/flr.v9i2.667 SN - 2295-3159 VL - 9 IS - 2 SP - 78 EP - 95 PB - EARLI ER - TY - CHAP A1 - Borggrafe, Andreas A1 - Ohndorf, Andreas A1 - Dachwald, Bernd A1 - Seboldt, Wolfgang T1 - Analysis of interplanetary solar sail trajectories with attitude dynamics T2 - Dynamics and Control of Space Systems 2012 N2 - We present a new approach to the problem of optimal control of solar sails for low-thrust trajectory optimization. The objective was to find the required control torque magnitudes in order to steer a solar sail in interplanetary space. A new steering strategy, controlling the solar sail with generic torques applied about the spacecraft body axes, is integrated into the existing low-thrust trajectory optimization software InTrance. This software combines artificial neural networks and evolutionary algorithms to find steering strategies close to the global optimum without an initial guess. Furthermore, we implement a three rotational degree-of-freedom rigid-body attitude dynamics model to represent the solar sail in space. Two interplanetary transfers to Mars and Neptune are chosen to represent typical future solar sail mission scenarios. The results found with the new steering strategy are compared to the existing reference trajectories without attitude dynamics. The resulting control torques required to accomplish the missions are investigated, as they pose the primary requirements to a real on-board attitude control system. Y1 - 2012 SN - 978-0-87703-587-9 SP - 1553 EP - 1569 PB - Univelt Inc CY - San Diego ER - TY - CHAP A1 - Borggräfe, Andreas A1 - Dachwald, Bernd T1 - Mission performance evaluation for solar sails using a refined SRP force model with variable optical coefficients T2 - 2nd International Symposium on Solar Sailing N2 - Solar sails provide ignificant advantages over other low-thrust propulsion systems because they produce thrust by the momentum exchange from solar radiation pressure (SRP) and thus do not consume any propellant.The force exerted on a very thin sail foil basically depends on the light incidence angle. Several analytical SRP force models that describe the SRP force acting on the sail have been established since the 1970s. All the widely used models use constant optical force coefficients of the reflecting sail material. In 2006,MENGALI et al. proposed a refined SRP force model that takes into account the dependancy of the force coefficients on the light incident angle,the sail’s distance from the sun (and thus the sail emperature) and the surface roughness of the sail material [1]. In this paper, the refined SRP force model is compared to the previous ones in order to identify the potential impact of the new model on the predicted capabilities of solar sails in performing low-cost interplanetary space missions. All force models have been implemented within InTrance, a global low-thrust trajectory optimization software utilizing evolutionary neurocontrol [2]. Two interplanetary rendezvous missions, to Mercury and the near-Earth asteroid 1996FG3, are investigated. Two solar sail performances in terms of characteristic acceleration are examined for both scenarios, 0.2 mm/s2 and 0.5 mm/s2, termed “low” and “medium” sail performance. In case of the refined SRP model, three different values of surface roughness are chosen, h = 0 nm, 10 nm and 25 nm. The results show that the refined SRP force model yields shorter transfer times than the standard model. Y1 - 2010 N1 - 2nd International Symposium on Solar Sailing, ISSS 2010, 2010-07-20 - 2010-07-22. New York City College of Technology of the City University of New York, USA SP - 1 EP - 6 ER -