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Picker routing in scattered storage warehouses: an evaluation of solution methods based on TSP transformations
No full textTo optimize their order fulfillment processes, many e-commerce warehouses employ a storage assignment strategy known as scattered or mixed-shelves storage. Under this approach, unit loads of homogeneous products are divided, and individual pieces are stored in various shelves throughout the warehouse. This arrangement ensures that products that appear together on unpredictable pick lists are stored in close proximity somewhere in the huge warehouses, reducing the travel distance for pickers. Despite these advancements, efficiently guiding pickers through the warehouse remains a significant planning challenge. Since the same products can be found in multiple storage positions, the traditional picker routing problem becomes more complex, as an additional selection task arises regarding which shelf to retrieve each requested product from. While previous research has developed several tailor-made solution algorithms, we demonstrate that known transformation schemes used for different variants of the well-known Traveling Salesman Problem (TSP) can be utilized to convert the single picker routing problem with scattered storage (SPRP-SS) into a classical TSP. This approach enables us to leverage the extensive array of state-of-the-art TSP solvers. The purpose of this paper is to explore the performance of these solvers when applied to solving the SPRP-SS. Through our computational study, we found that existing TSP solvers exhibit good performance, allowing near-optimal solutions to be obtained in less than a second for real-world scale SPRP-SS instances. Moreover, the efficiency of these TSP solvers remains unaffected by the number of cross aisles in the warehouse. Consequently, we exploit this flexibility to investigate the impact of cross aisles on picking performance in scattered storage warehouses
Milliwatt-scale 3D thermoelectric generators via additive screen printing
No full textElectronic components driving digitalization, such as wearables, Internet of Things (IoT), and Industry 4.0 systems, consume a growing portion of the global primary energy, largely relying on lithium-ion batteries. To enable a sustainable alternative, we explore cost-effective, fully printed thermoelectric generators (TEGs), which can be an alternative to batteries in low-power electronics. We here report a promising additive screen-printing method to fabricate two printed 3D TEGs (print-TEG I and print-TEG II) with varying thermocouple counts and a 0.36 fill factor, overcoming high contact resistance and thickness limitations. The print-TEGs were prepared via layer-by-layer printing of electrodes, interlayers, and n- and p-type legs, with six different layouts. Printed Ag₂Se as n-type legs and Bi₀.₅Sb₁.₅Te₃ as p-type legs were used for TEG fabrication. The print-TEG II with 50 thermocouples generates a maximum power output Pmax of 1.22 mW with an open circuit voltage, VOC of 268 mV for ΔT = 43 K. The print-TEG shows a highest power density Pd of 67 μW cm⁻² (>400 μW g⁻¹) for a fully printed planar TEG. The results demonstrate the potential of print-TEGs as a steadfast power source, guaranteeing nonstop operation of low-power electronic devices
Singularities of local models
No full textWe construct local models of Shimura varieties and investigate their singularities, with special emphasis on wildly ramified cases. More precisely, with the exception of odd unitary groups in residue characteristic 2 we construct local models, show reducedness of their special fiber, Cohen–Macaulayness and in equicharacteristic also (pseudo-)rationality. In mixed characteristic we conjecture their pseudo-rationality. This is based on the construction of parahoric group schemes over two dimensional bases for wildly ramified groups and an analysis of singularities of the attached Schubert varieties in positive characteristic using perfect geometry
SKA2 regulated hyperactive secretory autophagy drives neuroinflammation-induced neurodegeneration
No full textHigh levels of proinflammatory cytokines induce neurotoxicity and catalyze inflammation-driven neurodegeneration, but the specific release mechanisms from microglia remain elusive. Here we show that secretory autophagy (SA), a non-lytic modality of autophagy for secretion of vesicular cargo, regulates neuroinflammation-mediated neurodegeneration via SKA2 and FKBP5 signaling. SKA2 inhibits SA-dependent IL-1β release by counteracting FKBP5 function. Hippocampal Ska2 knockdown in male mice hyperactivates SA resulting in neuroinflammation, subsequent neurodegeneration and complete hippocampal atrophy within six weeks. The hyperactivation of SA increases IL-1β release, contributing to an inflammatory feed-forward vicious cycle including NLRP3-inflammasome activation and Gasdermin D-mediated neurotoxicity, which ultimately drives neurodegeneration. Results from protein expression and co-immunoprecipitation analyses of male and female postmortem human brains demonstrate that SA is hyperactivated in Alzheimer’s disease. Overall, our findings suggest that SKA2-regulated, hyperactive SA facilitates neuroinflammation and is linked to Alzheimer’s disease, providing mechanistic insight into the biology of neuroinflammation
Structural topology optimization with simultaneous stress and displacement constraints considering multiple load cases
No full textIn this paper, a structural topology optimization approach is presented considering stress and displacement constraints using different load cases. This is motivated by structural engineering applications. A short review on different types of constraints is presented, distinguishing respective measures on a global and local basis. It is identified that local stress and displacement constraints represent common engineering problems most closely and allow for a wide variety of applications, especially different displacement limits for different structural regions. In order to solve the proposed multiconstrained formulation, stress-constrained optimization with the Augmented Lagrangian method is extended to include displacement constraints simultaneously. The implementation of multiple load cases is discussed. This leads to a highly modular approach that can easily be adapted to different engineering problems. The corresponding gradient is derived and the optimization is performed using a steepest descent method. The effectiveness of this approach is proven based on the example of an L-shaped structure and a two-span beam
Green Ironmaking at Higher H₂ Pressure: Reduction Kinetics and Microstructure Formation During Hydrogen-Based Direct Reduction of Hematite Pellets
No full textHydrogen-based direct reduction (HyDR) of iron ores has attracted immense attention and is considered a forerunner technology for sustainable ironmaking. It has a high potential to mitigate CO₂ emissions in the steel industry, which accounts today for ~ 8–10% of all global CO₂ emissions. Direct reduction produces highly porous sponge iron via natural-gas-based or gasified-coal-based reducing agents that contain hydrogen and organic molecules. Commercial technologies usually operate at elevated pressure, e.g., the MIDREX process at 2 bar and the HyL/Energiron process at 6–8 bar. However, the impact of H₂ pressure on reduction kinetics and microstructure evolution of hematite pellets during hydrogen-based direct reduction has not been well understood. Here, we present a study about the influence of H₂ pressure on the reduction kinetics of hematite pellets with pure H₂ at 700 °C at various pressures, i.e., 1, 10, and 100 bar under static gas exposure, and 1.3 and 50 bar under dynamic gas exposure. The microstructure of the reduced pellets was characterized by combining X-ray diffraction and scanning electron microscopy equipped with electron backscatter diffraction. The results provide new insights into the critical role of H₂ pressure in the hydrogen-based direct reduction process and establish a direction for future furnace design and process optimization
Exploring the transition: biology, technology, and epistemic activities
No full textBy focusing on biorobotics, this article explores the epistemological foundations necessary to support the transition from biological models to technological artifacts. To address this transition, I analyze the position of the German philosopher Thomas Fuchs, who represents one possible approach to the problem of the relationship between bio-inspired technology and biology. While Fuchs defends the idea of a unique ontological space for humans, this article contends that his categorical distinctions face challenges in establishing a robust epistemic foundation necessary to ground the transition from biology to technology. After identifying at least three interwoven reasons for rejecting Fuchs’ epistemic foundation, I ask how, through what methods, and by means of which practices the newly bio-inspired object is accessed and shaped. Expanding on philosophy of science and technology in practice, I argue that the plurality of answers to this question provides a possible epistemological foundation within the different frameworks of practices that produce the bio-inspired object. In addressing the potential epistemological foundation for pluralistically grounding the transition from biological models to technological ones, my approach helps us: (i) concretize and examine the relationship between biological and technological models, and (ii) investigate the features and validity of bio-inspired objects, effectively offering a more concrete and pluralistic picture of what bio-inspired sciences and technologies are and what they can (or cannot) do
Sobolev regularity of bivariate isogeometric finite element spaces in case of a geometry map with degenerate corner
No full textWe investigate Sobolev regularity of bivariate functions obtained in Isogeometric Analysis when using geometry maps that are degenerate in the sense that the first partial derivatives vanish at isolated points. In particular, we show how the known C1-conditions for D-patches have to be tightened to guarantee square integrability of second partial derivatives, as required when computing finite element approximations of elliptic fourth order PDEs like the biharmonic equation
Experimentelle und rechnerisch validierte Methode zur Bestimmung der Mindesteinschraubtiefe von Schraubenverbindungen mit gefurchtem Mutterngewinde
No full textDie Einschraubtiefe und die Größe des Vorlochdurchmessers bestimmen neben dem Scherfestigkeitsverhältnis der eingesetzten Werkstoffe die quasi-statische Beanspruchbarkeit von Schraubenverbindungen mit gefurchtem Gewinde. Zur Validierung eines neuen Bewertungsansatzes zur Bestimmung der erforderlichen Mindesteinschraubtiefe werden Auszugsversuche mit variierter Einschraubtiefe und Gewindeüberdeckung für verschiedene Gewindetypen und Gewindegrößen durchgeführt. In Form des Beanspruchbarkeitsverhältnisses eines perfekt ausgeformten Gewindes und dem eines zu bewertenden Gewindes wird die Gewindeflankenüberdeckung des gefurchten Mutterngewindes in der Auslegung der erforderlichen Mindesteinschraubtiefe berücksichtigt
Stabilization of spline bases by extension
No full textWe present a method to stabilize bases with local supports by means of extension. It generalizes the known approach for tensor product B-splines to a much broader class of functions, which includes hierarchical and weighted variants of polynomial, trigonometric, and exponential splines, but also box splines, T-splines, and other function spaces of interest with a local basis. Extension removes elements that cause instabilities from a given basis by linking them with the remaining ones by means of a specific linear combination. The two guiding principles for this process are locality and persistence. Locality aims at coupling basis functions whose supports are close together, while persistence guarantees that a given set of globally supported functions, like certain monomials in the case of polynomial splines, remain in the span of the basis after extension. Furthermore, we study how extension influences the approximation power and the condition of Gramian matrices associated with the basis, and present a series of examples illustrating the potential of the method