TY - JOUR
AB - Regularization is used in many different areas of optimization when solutions
are sought which not only minimize a given function, but also possess a certain
degree of regularity. Popular applications are image denoising, sparse
regression and machine learning. Since the choice of the regularization
parameter is crucial but often difficult, path-following methods are used to
approximate the entire regularization path, i.e., the set of all possible
solutions for all regularization parameters. Due to their nature, the
development of these methods requires structural results about the
regularization path. The goal of this article is to derive these results for
the case of a smooth objective function which is penalized by a piecewise
differentiable regularization term. We do this by treating regularization as a
multiobjective optimization problem. Our results suggest that even in this
general case, the regularization path is piecewise smooth. Moreover, our theory
allows for a classification of the nonsmooth features that occur in between
smooth parts. This is demonstrated in two applications, namely support-vector
machines and exact penalty methods.
AU - Gebken, Bennet
AU - Bieker, Katharina
AU - Peitz, Sebastian
ID - 27426
IS - 3
JF - Journal of Global Optimization
TI - On the structure of regularization paths for piecewise differentiable regularization terms
VL - 85
ER -
TY - JOUR
AU - Alhaddad, Samer
AU - Förstner, Jens
AU - Grynko, Yevgen
ID - 43018
JF - Journal of Quantitative Spectroscopy and Radiative Transfer
KW - tet_topic_scattering
SN - 0022-4073
TI - Numerical study of light backscattering from layers of absorbing irregular particles larger than the wavelength
VL - 302
ER -
TY - CONF
AU - Hoffmann, Max
AU - Biehler, Rolf
ED - Trigueros, Marı́a
ED - Barquero, Berta
ED - Hochmuth, Reinhard
ED - Peters, Jana
ID - 31849
KW - Teaching and learning of specific topics in university mathematics
KW - Transition to
KW - across and from university mathematics
KW - Student Teachers
KW - Geometry
KW - Congruence
KW - Double Discontinuity.
T2 - Proceedings of the Fourth Conference of the International Network for Didactic Research in University Mathematics (INDRUM 2022, 19-22 October 2022)
TI - Student Teachers ’ Knowledge of Congruence before a University Course on Geometry
ER -
TY - CONF
AU - Florensa, Ignasio
AU - Hoffmann, Max
AU - Romo Vázquez, Avenilde
AU - Zandieh, Michelle
AU - Martínez-Planell, Rafael
ED - Trigueros, Marı́a
ED - Barquero, Berta
ED - Hochmuth, Reinhard
ED - Peters, Jana
ID - 43097
T2 - Proceedings of the Fourth Conference of the International Network for Didactic Research in University Mathematics (INDRUM 2022, 19-22 October 2022)
TI - Innovations in university teaching based on mathematic education research
ER -
TY - GEN
AU - Süßmann, Johannes
ID - 43186
TI - Pantheon
ER -
TY - JOUR
AB - Lightweight design is a common approach to reduce energy demand in the use stage of vehicles. The production of lightweight materials is usually associated with an increase in energy demand, so the environmental impacts of lightweight structures need to be assessed holistically using a life cycle assessment. To estimate the life cycle environmental impacts of a product in its developmental stage, for example, by life cycle engineering, future changes in relevant influencing factors must be considered. Prospective life cycle assessment provides methods for integrating future scenarios into life cycle assessment studies. However, approaches for integrating prospective life cycle assessment into product development are limited. The objective of this work is to provide the methodological foundation for integrating future scenarios of relevant influencing factors in the development of lightweight structures. The applicability of the novel methodology is demonstrated by a case study of a structural component in a steel, aluminium, and hybrid design. The results show that appropriate decarbonisation measures can reduce the life cycle greenhouse gas emissions by up to 95 percent until 2050. We also found that shifts in the environmentally optimal design are possible in future scenarios. Therefore, the methodology and data provided contribute to improved decision-making in product development.
AU - Ostermann, Moritz
AU - Grenz, Julian
AU - Triebus, Marcel
AU - Cerdas, Felipe
AU - Marten, Thorsten
AU - Tröster, Thomas
AU - Herrmann, Christoph
ID - 43464
IS - 8
JF - Energies
KW - Life Cycle Engineering
KW - Life Cycle Assessment
KW - Lightweight Design
KW - Prospective LCA
KW - Future-oriented LCA
KW - Energy System
KW - Material production
KW - Sustainable production
SN - 1996-1073
TI - Integrating Prospective Scenarios in Life Cycle Engineering: Case Study of Lightweight Structures
VL - 16
ER -
TY - JOUR
AB - A relatively small body of research has been conducted on the near- and long-term effects of study abroad (SA) to date. This existing research suggests that SA effects on language skills tend to be volatile, while the impact on various aspects of learners’ personal, academic, and professional development may be longer-lasting. Yet, learner perspectives on the dynamics and durability of such effects, in particular in the context of short-term SA programs, remain largely unexplored. This study hence investigates the near-term impact of short-term SA programs as experienced by students within the first months and years following their sojourns. A qualitative case-study design is employed to examine the accounts of four American students of German, who studied abroad in Austria for four weeks and were interviewed repeatedly over a period of up to 40 months after their sojourns. The results suggest that, from the students’ perspective, many effects deteriorate in the near term, although the overall sojourn experience still appears influential.
Abstract in German
Nur wenige Forschungsvorhaben haben sich bislang den mittel- bis langfristigen Auswirkungen studentischer Auslandsaufenthalte gewidmet; die bisherige Datenlage deutet jedoch darauf hin, dass die Auswirkungen auf sprachliche Kompetenzen eher unbeständig sind, wohingegen die persönliche, studiums- und berufsbezogene Entwicklung der Lernenden länger von einem Auslandsaufenthalt beeinflusst wird. Die Dynamik und Beständigkeit derartiger Auswirkungen wurden jedoch kaum mit Blick auf kurze Auslandsaufenthalte (≤ acht Wochen) sowie aus der Perspektive der Studierenden erforscht, was die vorliegende Studie insbesondere hinsichtlich mittelfristiger Effekte fokussiert. Mittels eines qualitativen Fallstudiendesigns werden die Interviewdaten vier amerikanischer Deutschlernender untersucht, die sich vier Wochen in Österreich aufhielten und in einem Zeitraum von bis zu 40 Monaten nach ihrem Aufenthalt wiederholt befragt wurden. Die Ergebnisse zeigen, dass viele Auswirkungen eines solchen Aufenthalts aus studentischer Perspektive mittelfristig verblassen, auch wenn der Auslandsaufenthalt im Gesamten weiterhin als einflussreiche Erfahrung wahrgenommen wird.
AU - Müller, Mareike
ID - 44058
IS - 1
JF - Frontiers: The Interdisciplinary Journal of Study Abroad
SN - 2380-8144
TI - Near-Term Effects of Short-Term Study Abroad: A Longitudinal Examination of Learner Perceptions
VL - 35
ER -
TY - JOUR
AB - Die Wirtschaftlichkeit von Wärmemotoren wird maßgeblich durch die Rückführung von Wärme in Rekuperatoren beeinflusst. Beim isobaren Expansionsmotor vom Bush-Typ, einem Wärmemotor, welcher bereits mit Wärmequellen ab 60°C betrieben werden kann, steigt der thermische Wirkungsgrad durch den Einsatz von Rekuperatoren signifikant. Gleichzeitig wirken sich das Fluidvolumen des Wärmeübertragers sowie der beim Betrieb auftretende Druckverlust negativ auf den thermischen Wirkungsrad aus. In dieser Arbeit wird der Zusammenhang von Totvolumen, Druckverlust und Wärmerückgewinnung untersucht und Empfehlungen für den Betrieb von Rekuperatoren am isobaren Expansionsmotor gegeben.
AU - Mügge, Nils
AU - Kronberg, Alexander
AU - Glushenkov, Maxim
AU - Kenig, Eugeny Y.
ID - 42252
IS - 5
JF - Chemie Ingenieur Technik
KW - Isobarer Expansionsmotor
KW - Dynamische Wärmeübertragungsmodellierung
KW - Phasenwechsel
KW - dichte Arbeitsmedien
TI - Untersuchung überlagerter Effekte von Druckverlust und Totvolumen durch Rekuperation am isobaren Expansionsmotor
VL - 95
ER -
TY - JOUR
AB - AbstractThe use of structured measuring systems to prevent wall slip is a common approach to obtain absolute rheological values. Typically, only the minimum distance between the measuring surfaces is used for further calculation, implying that no flow occurs between the structural elements. But this assumption is misleading, and a gap correction is necessary. To determine the radius correction $$\Delta r$$
Δ
r
for specific geometries, we conducted investigations on three Newtonian fluids (two silicon oils and one suspension considered to be Newtonian in the relevant shear rate range). The results show that $$\Delta r$$
Δ
r
is not only shear- and material-independent, but geometry-dependent, providing a Newtonian flow behaviour in a similar viscosity range. Therefore, a correction value can be determined with only minute deviations in different Newtonian fluids. As the conducted laboratory measurements are very time-consuming and expensive, a CFD-approach with only very small deviations was additionally developed and compared for validation purposes. Therefore, simulation is an effective and resource-efficient alternative to the presented laboratory measurements to determine $$\Delta r$$
Δ
r
for the correction of structured coaxial geometries even for non-Newtonian fluids in the future.
AU - Josch, Sebastian
AU - Jesinghausen, Steffen
AU - Dechert, Christopher
AU - Schmid, Hans-Joachim
ID - 36983
JF - Rheologica Acta
KW - rheology
KW - rheometry
KW - suspension
KW - coaxial
KW - correction
SN - 0035-4511
TI - Experimental and simulative determination and correction of the effective gap extension in structured coaxial measuring systems
ER -
TY - CONF
AB - We present an approach for guaranteed constraint satisfaction by means of data-based optimal control, where the model is unknown and has to be obtained from measurement data. To this end, we utilize the Koopman framework and an eDMD-based bilinear surrogate modeling approach for control systems to show an error bound on predicted observables, i.e., functions of the state. This result is then applied to the constraints of the optimal control problem to show that satisfaction of tightened constraints in the purely data-based surrogate model implies constraint satisfaction for the original system.
AU - Schaller, Manuel
AU - Worthmann, Karl
AU - Philipp, Friedrich
AU - Peitz, Sebastian
AU - Nüske, Feliks
ID - 30125
IS - 1
T2 - IFAC-PapersOnLine
TI - Towards reliable data-based optimal and predictive control using extended DMD
VL - 56
ER -