Technische Universität Dresden: Qucosa
Not a member yet
16344 research outputs found
Sort by
Bildung für nachhaltige Entwicklung (BNE) in der universitären Lehrkräftebildung in Deutschland: Stand und Perspektiven
No full textBildung für nachhaltige Entwicklung (BNE) als zentrales Element der Lehrkräftebildung zielt ab auf die Vorbereitung angehender Lehrkräfte, zukunftsfähige Bildung zu gestalten. In den Sustainable Development Goals (SDGs) wurde die Lehrkräftebildung unter dem vierten Ziel („Ensure inclusive and equitable quality education and promote lifelong learning opportunities for all“) als 4.7 verankert
Analysis of resilience strategies and ripple effect in blockchain-coordinated supply chains: an agent-based simulation study
No full textResilience enables supply chains to reduce their proneness to disruptions and recover faster. Many existing strategies to strengthen the resilience of supply chains are facilitated by the use of digital technology. Blockchain, as one of the promising innovative technologies, enables a transparent, secure, and timely data exchange and automation via smart contracts. In this paper, we discuss the impact of blockchain technology on supply chain risk management and, in particular, on supply chain resilience. We identify potential risk-related blockchain application scenarios and examine their impact on the existing resilience strategies. We explore the impact of the most promising applications with respect to resilience by using an agent-based simulation model of a complex supply network affected by disruptions. The theoretical analysis reveals a promotion of supply chain resilience strategies, especially if smart contracts are used for risk-related collaboration. The simulation study indicates an increase in resilience if the underlying collaboration is based on time-efficient processes: The propagation of disruptions, the network recovery time, and total costs can be substantially reduced. However, depending on the duration of the disruption, negative effects can occur if process efficiency is insufficient. From our investigations, we derive insights for managers who are interested in practical implementation
Berry curvature induced transport phenomena on crystal surfaces
No full textThe Berry curvature (BC) associated with electronic band-like states is a fundamental quantity that gives rise to an anomalous electronic velocity and interesting (nonlinear) electronic, heat, and spin-transport properties. BC is a key concept in understanding and predicting physical properties of crystalline materials and, therefore, one of central quests of modern material design is to find mechanisms that can lead to large enhancements of BC. Typically, large BC concentrations occur at points in the Brillouin zone (BZ) where two bands are exactly or nearly degenerate, leading to rapid changes of the Bloch wave functions near such hot spots. Classic examples of such BC hot spots include the Weyl nodes in 3D materials and the Dirac points in 2D graphene.
Inside a solid, the anomalous velocity of Bloch electrons caused by the electronic BC leads to a sideways deflection of currents, much as an external magnetic field. Such a current deflection caused by the intrinsic electronic structure of a material and its associated Hall-type response must be allowed by the symmetries of the system. It is well-known that an absence of magnetism, and consequently a presence of time-reversal symmetry in the electronic band structure, leads to zero total BC, integrated over BZ momenta. This consequently prevents any linear Hall response. However, as long as at least lattice inversion symmetry is broken, a finite BC is associated with the electronic structure, which can then allow, e.g. a quantum nonlinear Hall effect where the observed transversal voltage is proportional to the applied current squared. This nonlinear response is related to the dipole moment of the BZ integrated BC, the BC dipole. However, for materials with both time-reversal invariance and inversion, the BC vanishes identically at all momenta in the 3D BZ.
In this thesis, I show that surface states can have -compared to a pure 2D system- an additional contribution to the BC which depends on the variance of the penetration length of the state into the bulk. Large BC contributions can arise which grow as the surface state penetrates deeper into the bulk and progressively attains more bulk character. This effect and its dependence on the surface structure and symmetry distinguishes the surface states’ BC obviously from its bulk counterpart. I demonstrate that the surface Fermi arc states of tilted Weyl semimetals (WSMs) are perfect candidates to observe this enhanced surface BC. The divergence of BC occurs not at a point, but instead over an entire line in the surface BZ, which I will refer to as a BC “hot line.” These hot lines emerge in the surface BZ of WSMs, and they separate the 2D states that are localized at the surface from the continuum of 3D bulk states. The topology of the Weyl system forces the Fermi arcs to end at such a hot line leading to a gigantic contribution to the BC driven nonlinear Hall effect. It features a contribution to the BC dipole that grows linearly proportionally with the thickness of a WSM slab. Thus, these findings not only enhance the understanding of the geometrical aspects of the Fermi arcs’ electronic structure, but should also be experimentally relevant in all BC driven phenomena in WSM.
At a first glance, time-reversal and inversion symmetric materials seem to become uninteresting from the BC point of view as their BC and anomalous electron velocities appear to vanish. I demonstrate that while this conclusion is valid for 3D bulk materials, at surfaces and interfaces of these the opposite holds: at a general Miller index surfaces Bloch-electrons do attain a finite anomalous velocity, also for materials with bulk inversion and time-reversal symmetry. Indeed, as a general rule of thumb, the surface BC vanishes only at unreconstructed low Miller index surfaces, whereas a finite surface BC associated with any higher index surface, including miscut and vicinal ones with surface steps that break two-fold rotations around the surface normal and, thus, lack inversion symmetry. If there is, in addition, not more than one mirror plane containing the normal, a finite surface BC dipole forms. Very many elementary surfaces fulfill this symmetry requirement. This will be demonstrated by first principles calculations of the BC at bismuth, HgTe and rhodium surfaces of various symmetries. Again, this opens up a plethora of materials to explore and harness the physical effects emerging from the electronic BC associated exclusively with their boundaries
Effectiveness of responsive pricing in the face of supply chain disruptions
No full textDisruptions of the material flow can cause serious financial damage for supply chain partners to the extent of even jeopardizing their survival. To cope with this hazard, several proactive and reactive mitigation strategies have been suggested in the research literature of supply chain risk management. To our knowledge, only back-up supply and structural changes of the information flow have been incorporated by network level simulation models. Moreover, a detailed assessment of the disruption length’s effect on the resulting costs of a disruption is still missing. We have conducted a simulation study with system dynamics, split into three simulation experiments, to quantify the disruption costs subject to various disruption lengths and to evaluate the effectiveness of responsive pricing regarding the costs saved as well as the order fulfillment rate. We have analyzed the height of the price change and the operating time of this reactive strategy to be able to provide insights into the general behavior of the system and the strategy. For this purpose and since no real supply chain data has been available, we have extended the approach of Wilson (2007) to a two-product model with monetary parameters. A uniform space-filling approach combined with Kriging interpolation has been selected to create response surfaces for two of our three research questions. Our study reveals that there is a disproportionate influence of the disruption length on the overall disruption costs. In our model, the effect of the height of the price change is significant. The ideal height of price change initially increases for longer disruptions until an optimum range is reached. The operating time of the price change has a smaller effect on the effectiveness. Despite the fact that the effectiveness can be further optimized by considering the operating time, our study indicates that near-optimum results can be obtained by having responsive pricing in effect for the acute time span of the disruption
Integrated slicing tree approach for solving the facility layout problem with input and output locations based on contour distance
No full textThe designer of a plant layout faces mutually dependent subproblems that are traditionally solved in a sequential process. In this paper, a slicing tree based parallel tempering heuristic is used to solve the facility layout problem, including the location of the material handling points of each facility. To determine the input and output points on the perimeters of the departments for a given layout, two heuristic methods are presented and compared to an integer linear programming approach. The shortest paths along the perimeter of the departments are used to calculate the distance of the material flow paths from output to input points. The methods are embedded in a superordinate parallel tempering algorithm, which represents a novel approach to solving the facility layout problem. To compare the efficiency of the superordinate parallel tempering algorithm, two variants of the variable neighbourhood search are implemented as well. The effectiveness of the approach in terms of the objective function value is shown by comparing the results to those in the literature
Analysis on Braess paradox and network design considering parking in the autonomous vehicle environment
No full textThis study is the first in the literature to examine the Braess paradox considering parking behavior in the autonomous vehicle (AV) environment, based on which the network design problem for the autonomous transportation system (NDP-ATS) is modeled. First, we introduce the AV commuting pattern considering the self-driving process for the parking purpose. We then illustrate the existence of two distinct Braess paradoxes that can occur in AV traffic networks with regards to parking space addition and network capacity expansion. They show that these two types of “improvement” measures might deteriorate the network system performance in an AV situation. Second, motivated to avoid the deterioration due to the introduced Braess paradoxes, we develop a bi-level programming model for NDP-ATS. The lower-level program addresses the network-equilibrium traffic assignment for AVs. The upper-level program aims to minimize the network-wide travel cost considering both occupied and empty AV trips by selecting the optimal design option accounting for road capacity enhancement and parking facility deployment simultaneously. To solve the developed bi-level model, the simplicial homology global optimization algorithm is employed along with the Frank–Wolfe algorithm and the CPLEX. Finally, the efficacy of the modeling framework is validated through case studies on the Sioux Falls city network and the Anaheim network. The results show that the developed methodology is capable of producing high-quality solutions with respect to savings in system-level travel costs for AV traffic. The results also highlight the impacts of parking fees on the system performance for the optimized network. Additionally, it is found that the two objectives, which minimize the total system travel cost and minimize that for empty AV trips only, are conflicting for certain scenarios. The methodological approach introduced in this work serves as a critical modeling device for infrastructure development and policy assessment for AV traffic
„Aus dem Kursraum an den Strand“ – eine empirische Analyse der Wirksamkeit mediengestützter Erholungsaktivitäten in der Hochschule
No full textDigital LifeAus dem Text: Erholung ist ein zentraler Prozess, um den im Arbeitsalltag verorteten Belastungen entgegenzuwirken, Ressourcen zu regenerieren, sich zu entspannen und einen Ausgleich zu beruflichen Anforderungen zu schaffen (Sonnentag & Fritz, 2004). Dem funktionalen Umgang mit Stress, dem Schaffen von Erholungsmöglichkeiten und der daraus resultierenden Vermeidung von Befindensbeeinträchtigungen kommen nicht nur in der heutigen Arbeitswelt eine immer wichtigere Bedeutung zu, sondern werden auch für den Hochschulkontext und die Studierenden zunehmend relevanter (Middendorff et al. 2017). Lehr- und Lernkontexte spielen bislang im Hinblick auf gesundheitsförderliche Arbeitsgestaltung allerdings eher eine untergeordnete Rolle (ebd.)
Activation of the cGAS/STING Axis in Genome-Damaged Hematopoietic Cells Does Not Impact Blood Cell Formation or Leukemogenesis
No full textGenome damage is a main driver of malignant transformation, but it also induces aberrant inflammation via the cGAS/STING DNA-sensing pathway. Activation of cGAS/STING can trigger cell death and senescence, thereby potentially eliminating genome-damaged cells and preventing against malignant transformation. Here, we report that defective ribonucleotide excision repair (RER) in the hematopoietic system caused genome instability with concomitant activation of the cGAS/STING axis and compromised hematopoietic stem cell function, ultimately resulting in leukemogenesis. Additional inactivation of cGAS, STING, or type I IFN signaling, however, had no detectable effect on blood cell generation and leukemia development in RER-deficient hematopoietic cells. In wild-type mice, hematopoiesis under steady-state conditions and in response to genome damage was not affected by loss of cGAS. Together, these data challenge a role of the cGAS/STING pathway in protecting the hematopoietic system against DNA damage and leukemic transformation.
Significance:
Loss of cGAS/STING signaling does not impact DNA damage–driven leukemogenesis or alter steady-state, perturbed or malignant hematopoiesis, indicating that the cGAS/STING axis is not a crucial antioncogenic mechanism in the hematopoietic system
Integration einer VDA 5050 konformen Leitsteuerung in ein Simulationsmodell für AGV-Systeme
No full textThis paper presents the development of a communication interface between simulated Automated Guided Vehicles (AGVs) and a proprietary master control, based on the VDA 5050 universal communication interface. This approach allows the evaluation of a proprietary master control systems quality through the simulation results. The implementation includes the openTCS master control, the WITNESS Horizon simulation software, and a Python-based adapter program, specially developed for this purpose. Finally, a real life production scenario is used as an application example to validate the interface. This paper concludes with a discussion of the successfully validated interface, as well as insights gained and further considerations