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Sustainability is more than resource efficiency – SDGs as a guide to a holistic sustainability strategy
No full textGetrieben durch Nachfrage und auch Regulierung, gewinnt Nachhaltigkeit in der Produktion zunehmend an Bedeutung. Der Beitrag zeigt anhand der UN-Nachhaltigkeitsziele (SDGs) auf, dass eine ganzheitliche Nachhaltigkeitsstrategie über den aktuellen Fokus der Ressourceneffizienz und die Anwendung bestehender Werkzeuge und Methoden hinausgeht. Eine frühzeitige und ganzheitliche Betrachtung erlaubt das Schöpfen von umfassenden Innovationspotenzialen und sichert einen langfristigen Wettbewerbsvorteil.Driven by demand and regulation, sustainability is becoming increasingly important in production. This article uses the UN Sustainable Development Goals (SDGs) to show that a holistic sustainability strategy goes beyond the current focus on resource efficiency and the use of existing tools and methods. An early and holistic approach allows the realisation of comprehensive innovation potential and ensures a long-term competitive advantage
The influence of the modeling order on the predictable area of non-linear unidirectional ocean waves
No full textThe influence of non-linear modeling of phase-resolved ocean wave fields on the extent of the accessible predictable area is investigated. Assuming that the ocean surface dynamics is known over a limited spatial domain, e.g. via radar backscatter reconstruction, the linear wave theory as well as the high-order spectral method with various orders of non-linearity are used to propagate the surface with different levels of physical fidelity. The prediction accuracy is quantified by comparing the predicted waves to a reference, i.e. a fully known wave field propagated with a high-fidelity wave model. By doing this, it is made possible to track the spatiotemporal evolution of the prediction accuracy and define the predictable area as the region over which the accuracy is higher than a threshold, here defined by a “surface similarity parameter” lower than 0.1. Different unidirectional wave field characteristics are studied, highlighting the effect of the wave steepness, water depth and wave energy spreading around the peak spectral frequency, all impacting significantly the prediction accuracy, thus the predictable area. It is shown that the extent of the predictable area is highly dependent on the order of the considered wave model, and that the third order generally leads to the largest reachable predictable area in all configurations
Multilayer substrate integrated waveguide six-port junctions with embedded resistive films
No full textThis article deals with multilayer substrate integrated waveguide (SIW) six-port junctions with embedded carbon resistive films. SIW six-ports usually employ reactive power dividers, which degrade the amplitude and phase balance when the six-port is terminated with mismatched power detectors. The associated impairments are studied and two SIW six-port junctions with improved isolation and output matching are designed for K-/Ka-band applications to overcome these limitations. The proposed designs differ with respect to the configuration of the output ports making the underlying six-port topology applicable for different layout requirements. Measurements of the fabricated components validate the concept. The six-ports are compact, fully shielded and can be integrated in multilayer printed circuit boards
Hydraulische Leistungsfähigkeit von eingestauten und überströmten Brücken über Fließgewässer mit mildem Gefälle und kompaktem Querschnitt
No full textFür den Ein- und Überstau von Brücken mit lateraler Einschnürung bei Extremhochwasser fehlen physikalisch basierte, hydraulische Berechnungsverfahren. Situationsübergreifend einheitlich wird in dieser Arbeit die Impulsgleichung mit nicht-linearen Verteilungen messbarer Größen an Kontrollvolumenrändern verwendet. Polynomiale Approximationen für im Labor und CFD-Modell bestimmte Verteilungen ermöglichen eine einfache Behandlung der Randintegrale der Schnittgrößen bei der praktischen Berechnung ohne bauwerksindividuelle Beiwerte.There is a lack of physically based hydraulic computation methods for submerged and overtopped bridges during extreme floods with lateral constriction. In this work, the momentum equation is used uniformly across different hydraulic situations utilizing non-linear distributions of measurable quantities at control volume boundaries. Polynomial approximations for distributions determined in the laboratory and CFD model allow a simple treatment of the boundary integrated forces in the practical calculation without structure individual coefficients
Rapid detachment of a rigid sphere adhered to a viscoelastic substrate: An upper bound model incorporating Maugis parameter and preload effects
No full textFor a typical adhesive contact problem, a rigid sphere initially adhered to a relaxed viscoelastic substrate is pulled away from the substrate at finite speeds, and the pull-off force is often found to depend on the rate of pulling. Despite significant theoretical advancements in this area, how the apparent adhesion enhancement is affected by the Maugis parameter and preload remains unclear, and existing models are sometimes contentious. In this work, we revisit this adhesive contact problem and propose a theoretical model to predict the upper bound detachment behavior when the pulling speed approaches infinity. Our analysis reveals that the apparent work of adhesion can always be enhanced, regardless of the Maugis parameter, when the initial contact radius exceeds a critical threshold. Conversely, when the initial contact radius is below this critical value, the adhesion enhancement becomes limited and depends on both the Maugis parameter and the preload condition. Further model calculations suggest that the critical initial contact radius is dependent on the Maugis parameter. In the JKR-like regime, this critical radius converges to a constant value, whereas in the DMT-like regime, it diverges rapidly following an inverse power law with respect to the Maugis parameter. As a result, observing adhesion enhancement is generally more challenging in DMT-like contacts compared to JKR-like contacts. In the meantime, our model also suggests that the adhesion enhancement arises from the expansion of the cohesive zone area due to the viscoelastic properties of the material not only within the cohesive zone but also in the intimate contact zone. Overall, our findings offer a more comprehensive understanding of viscoelastic effects in adhesive contacts, which can be used to rationally predict or optimize adhesion strength in viscoelastic interfaces
Expectations vs. reality in nacre-like composites: dominating role of particle packing and polymer confinement in mechanical performance
No full textAfter decades of research, mimicking the intricate structure of nacre shells with flawlessly packed blocks remains a laborious task in composite material design. For practical reasons, less ideal alternatives with reduced packing densities below 70 vol.% are often being explored. However, the extent to which the features of the nacre structure can be exploited remains unclear. This paper investigates whether mimicking nacre design in non-densely packed composites can still deliver exceptional mechanical performance. A wide range of ceramic particles (80–100 µm, including spheres and platelets) and methacrylate-based polymers was studied. All the composites exhibited little variation in strength (100–150 MPa) and E-modulus regardless of hierarchical structure, particle size, shape, or interfacial bonding, highlighting the greater importance of particle packing over these factors for ceramic loadings below 65 vol.%. In particular, the benefits of micron-sized anisotropic particles were diminished by the fundamental challenges in aligning such blocks: although these assemblies significantly enhanced fracture resistance, the elastic modulus was still lower than expected (25 GPa). A polydisperse mixture of irregularly shaped micron-sized particles surprisingly achieved a high elastic modulus of 20 GPa, suggesting that an optimized size distribution can provide benefits comparable to those of particle anisotropy. Composites loaded with small particles (< 500 nm) exhibited two key effects: the solvation shells contributed to the total organic content significantly, limiting the maximum ceramic loading, and the polymer confined within small interparticle voids exhibited increased stiffness, leading to more brittle fracture despite the abundance of organic phase. Both phenomena should be accounted for in theoretical simulations and the practical design of composite materials
Design and optimization of stirrer and mixer design for the correct mixing of pharmaceutical powders through DEM
No full textMixing of granular materials is an important process for pharmaceutical industries. In this study, a quantifiable calculation method was suggested to determine the final mixing degree of the mixture. Based on that, the effect of the stirrer design, rotational speed, powder density, cohesivity, material ratios, and particle movement in the chamber guided through different designs of deflectors on the final mixing quality is examined. The results show that increasing the stirring speed, generates better mixing quality. However, introducing a varying rotational speed mode improves the mixing degree specially for binary mixtures with high relative densities. The improvement of the mixing with the number of contacting blades is observed. Finally, the introduction of a simple deflector drastically enhances the mixing quality and enables the feeding into the chamber, which is key for continuous operation with cohesive powders, making the process more stable and efficient by using more of the mixing volume
Finite algebras with hom-sets of polynomal size
No full textWe provide an internal characterization of those finite algebras (i.e., algebraic structures) A such that the number of homomorphisms from any finite algebra X to A is bounded from above by a polynomial in the size of X. Namely, an algebra A has this property if, and only if, no subalgebra of A has a nontrivial strongly abelian congruence. We also show that the property can be decided in polynomial time for algebras in finite signatures. Moreover, if A is such an algebra, the set of all homomorphisms from X to A can be computed in polynomial time given X as input. As an application of our results to the field of computational complexity, we characterize inherently tractable constraint satisfaction problems over fixed finite structures, i.e., those that are tractable and remain tractable after expanding the fixed structure by arbitrary relations or functions
Robust performance analysis of cooperative control dynamics via integral quadratic constraints
No full textWe study cooperative control dynamics with gradient based forcing terms. As a specific example, we focus on source-seeking dynamics with vehicles embedded in an unknown scalar field with a subset of agents having gradient information. We consider time-invariant and uncertain interaction potentials common in formation control and flocking. We leverage the framework of α -integral quadratic constraints to obtain convergence rate estimates whenever exponential stability can be achieved. Sufficient conditions take the form of linear matrix inequalities independent of the size of network. A derivation (purely in time-domain) of the so-called hard Zames-Falb α -IQCs involving general non-causal higher order multipliers is given along with a suitably adapted parameterization of the multipliers to the α -IQC setting. Numerical examples illustrate the application of theoretical results
A rigorous optimization method for long-term multi-stage investment planning: Integration of hydrogen into a decentralized multi-energy system
No full textThoroughly assessing future energy systems requires examining both their end states and the paths leading to them. Employing dynamic investment or multi-stage optimization models is crucial for this analysis. However, solving these optimization problems becomes increasingly challenging due to their long time horizons – often spanning several decades – and their dynamic nature. While simplifications like aggregations are often used to expedite solving procedures, they introduce higher uncertainty into the results and might lead to suboptimal solutions compared to non-simplified models. Against this background, this paper presents a rigorous optimization method tailored for multi-stage optimization problems in long-term energy system planning. By dividing the solution algorithm into a design and operational optimization step, the proposed method efficiently finds feasible solutions for the non-simplified optimization problem with simultaneous quality proof. Applied to a real-life energy system of a waste treatment plant in Germany, the method significantly outperforms a benchmark solver by reducing the computational time to find the first feasible solution from more than two weeks to less than one hour. Furthermore, it exhibits greater robustness compared to a conventional long-term optimization approach and yields solutions closer to the optimum. Overall, this method offers decision-makers computationally efficient and reliable information for planning investment decisions in energy systems