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General, efficient, and robust Hamiltonian engineering
No full textImplementing the time evolution under a desired target Hamiltonian is critical for various applications in quantum science. Due to the exponential increase of parameters in the system size and due to experimental imperfections, this task can be challenging in quantum many-body settings. We introduce an efficient and robust scheme to engineer arbitrary local many-body Hamiltonians. To this end, our scheme applies single-qubit π or π/2 pulses to an always-on system Hamiltonian, which we assume to be native to a given platform. These sequences are constructed by efficiently solving a linear program (LP) which minimizes the total evolution time. In this way, we can engineer target Hamiltonians that are only limited by the locality of the interactions in the system Hamiltonian. Based on average Hamiltonian theory and by using robust composite pulses, we make our schemes robust against errors, including finite-pulse-time errors and various control errors. To demonstrate the performance of our scheme, we provide numerical simulations. In particular, we solve the Hamiltonian-engineering problem on a laptop for arbitrary two-local Hamiltonians on a two-dimensional square lattice with 196 qubits in only 60 s. Moreover, we simulate the engineering of general Heisenberg Hamiltonians from Ising Hamiltonians with imperfect single-qubit pulses for smaller system sizes, and achieve a fidelity larger than 99.9%, which is orders of magnitude better than nonrobust implementations
Rethinking global soil degradation: drivers, impacts, and solutions
No full textThe increasing threat of soil degradation presents significant challenges to soil health, especially
within agroecosystems that are vital for food security, climate regulation, and economic stability. This growing
concern arises from intricate interactions between land use practices and climatic conditions, which, if not
addressed, could jeopardize sustainable development and environmental resilience. This review offers a
comprehensive examination of soil degradation, including its definitions, global prevalence, underlying
mechanisms, and methods of measurement. It underscores the connections between soil degradation and land
use, with a focus on socio‐economic consequences. Current assessment methods frequently depend on
insufficient data, concentrate on singular factors, and utilize arbitrary thresholds, potentially resulting in
misclassification and misguided decisions. We analyze these shortcomings and investigate emerging
methodologies that provide scalable and objective evaluations, offering a more accurate representation of soil
vulnerability. Additionally, the review assesses both physical and biological indicators, as well as the potential
of technologies such as remote sensing, artificial intelligence, and big data analytics for enhanced monitoring
and forecasting. Key factors driving soil degradation, including unsustainable agricultural practices,
deforestation, industrial activities, and extreme climate events, are thoroughly examined. The review
emphasizes the importance of healthy soils in achieving the United Nations Sustainable Development Goals,
particularly concerning food and water security, ecosystem health, poverty alleviation, and climate action. It
suggests future research directions that prioritize standardized metrics, interdisciplinary collaboration, and
predictive modeling to facilitate more integrated and effective management of soil degradation in the context of
global environmental changes
Electromechanical computational model of the human stomach
No full textThe stomach plays a central role in digestion through coordinated muscle contractions, known as gastric peristalsis, driven by slow-wave electrophysiology. Understanding this process is critical for treating motility disorders such as gastroparesis, dyspepsia, and gastroesophageal reflux disease. Computer simulations can be a valuable tool to deepen our understanding of these disorders and help to develop new therapies. However, existing approaches often neglect spatial heterogeneity, fail to capture large anisotropic deformations, or rely on computationally expensive three-dimensional formulations. We present here a computational framework of human gastric electromechanics, that combines a nonlinear, rotation-free shell formulation with a constrained mixture material model. The formulation incorporates active-strain, constituent-specific prestress, and spatially non-uniform parameter fields. Numerical examples demonstrate that the framework can reproduce characteristic features of gastric motility, including slow-wave entrainment, conduction velocity gradients, and large peristaltic contractions with physiologically realistic amplitudes. The proposed framework enables robust electromechanical simulations of the whole stomach at the organ scale. It thus provides a promising basis for future in silico studies of both physiological function and pathological motility disorders
Tailoring polysaccharide-based aerogels for potential food applications: Structural and hydration characterization by NMR relaxometry and diffusometry
No full textPolysaccharide-based aerogels are promising candidates for food-related applications due to their high surface area, adjustable porosity, biocompatibility, and biodegradability. The present study investigated chitosan, sodium alginate, and xanthan gum aerogels obtained by supercritical CO2 drying. Each polysaccharide exhibited unique structural and physicochemical behavior depending on polymer concentration, which influenced the final aerogel properties such as bulk density, pore size, surface area, and water absorption. NMR relaxometry and diffusometry were employed for a detailed characterization of pore structure, hydration behavior, and molecular mobility. Results revealed that, in contrast to alginate aerogels, lower polymer concentrations in chitosan led to more open networks with larger pores and higher surface areas, making them more suitable for applications such as filtration, adsorption, or active compound delivery. On the other hand, xanthan gum aerogels formed denser, more crosslinked structures, yielding high water absorption rate suitable for controlled release or encapsulation purposes. A hybrid chitosan/alginate aerogel successfully combined the advantageous properties of both components, resulting in low-density materials with enhanced porosity and mechanical integrity. The difference in aerogel structures obtained by different polysaccharides highlights the possibility of tailoring aerogel properties for specific food applications, from active packaging to edible carriers or moisture regulators. Given the need for safer, biodegradable, and versatile materials in the food industry, this study highlights the importance of designing aerogels based on the material type and offers a practical guide for producing them using scalable and safe methods
Impacts of land use change on nutrient balance and greenhouse gas emissions: a regional perspective
No full textNutrient balance is critical for sustainable land management, yet information scarcity hampers its systematic evaluation of trade-offs among alternate land uses. We employed a detailed regional nutrient dataset collected from 70 monitoring sites over 16 years to conduct a comprehensive analysis of yields, nutrient balances and greenhouse gas emissions associated with different land management practices in Lower Saxony, Germany. The information was used to develop land use transformation scenarios while assessing their impacts on regional nutrient balances and emissions. Our analysis demonstrated that organic farming exhibited lower nutrient surpluses but also lower yields compared to conventional systems, while grazing systems showed the highest nutrient outputs. A comparison with other regional studies highlights the importance of unique combinations of climate, soil, management practices, and socioeconomic settings in developing sustainable land management strategies – a global perspective, while useful in setting goals, may not capture local needs specific to this combination of factors
From the titanic era to the AI era: smart technology to drive green transformation in shipping
No full textMaritime transportation, although highly efficient, remains carbon-intensive and must undergo substantial transformation to achieve decarbonisation and ultimately emission-free operation by the 2050 regulatory target. Given the typical 25-year design life of ships, this transition requires both continuous retrofitting of the existing fleet and the integration of new technologies in newbuilds at varying levels of readiness. Currently, the feasibility of carbon- and emission-free solutions depends largely on the availability of alternative fuels, whose limited supply and demand result in high costs and price volatility. In parallel, optimisation of onboard energy systems remains crucial. Technologies, such as heat pumps, direct-current grids, wind-assisted propulsion and advanced route optimisation, provide practical pathways to improved efficiency and reduced emissions. This paper reviews these technologies and discusses the key challenges to achieving emission-free shipping
On Sinkhorn's DAD theorem and the self-consistency equation in COSMO-based activity coefficient models
No full textIn a 1966 paper, Sinkhorn proved that for any real square matrix A which has only positive entries there exists a uniquely determined real diagonal matrix D with positive diagonal entries such that :=DAD is stochastic, i.e. all row sums of B are equal to 1. Moreover, Sinkhorn stated an iterative method for computing D. Nowadays, Sinkhorn's result and its variants are often referred to as DAD theorems. The purpose of this article is twofold. On the one hand, we give the link between Sinkhorn's DAD theorem and the self-consistency equation in COSMO-based activity coefficient models in chemical engineering. On the other hand, we give a new constructive proof of Sinkhorn's DAD theorem by using classical fixed-point theory. Hereby, the larger class of nonnegative matrices with positive diagonal is considered. Our proof uniformly provides convergence for a number of iterative methods for computing D. Some of them are used in practice although, to the best of our knowledge, a formal proof of convergence is missing
Status of the TransiEnt Library: Transient simulation of complex integrated energy systems
No full textThe TransiEnt Library is an open-source Modelica Libraryoriginally developed at the Hamburg University ofTechnology. It is a flexible framework for modelling andanalysing the dynamic behaviour of coupled energy systemsunder current and future scenarios. With the addition ofthree new members to the TransiEnt Library consortium,namely Fraunhofer UMSICHT, Gas- und Wärme-InstitutEssen~e.V. and XRG Simulation GmbH, the TransiEnt Libraryhas expanded its portfolio of models and methods forinvestigating the challenges in energy systems. Buildingupon the previous status report, this article presents thelatest developments in the TransiEnt library, highlithingits extended capabilities to model and simulate large,complex energy systems. The recent developments include theautomatic generation of aggregated models at district andregionals levels, as well as the modelling of medium- andlow-voltage electrical distribution networks. In addition,new concepts for the representation of large-scale heatingnetworks have been developed and are presented alongsideillustrative use cases
Deformation by design: data-driven approach to predict and modify deformation in thin Ti-6Al-4V sheets using laser peen forming
No full textAbstract: The precise bending of sheet metal structures is crucial in various industrial and scientific applications, whether to modify deformation in an existing component or to achieve specific shapes. Laser peen forming (LPF) is proven as an innovative forming process for sheet metal applications. LPF involves inducing mechanical shock waves into a specimen that deforms the affected region to a certain desired curvature. The degree of deformation induced after LPF depends on numerous experimental factors such as laser energy, the number of peening sequences, and the thickness of the specimen. Consequently, comprehending the complex dependencies and selecting the appropriate set of LPF process parameters for application as a forming or correction process is crucial. The main objective of the present work is the development of a data-driven approach to predict the deformation obtained from LPF for various process parameters. Artificial neural network (ANN) was trained, validated, and tested based on experimental data. The deformation obtained from LPF is successfully predicted by the trained ANN. A novel process planning approach is developed to demonstrate the usability of ANN predictions to obtain the desired deformation in a treated region. The successful application of this approach is demonstrated on three benchmark cases for thin Ti-6Al-4V sheets, such as deformation in one direction, bi-directional deformation, and modification of an existing deformation in pre-bent specimens via LPF. Graphical abstract: [Figure not available: see fulltext.]
Geometry smoothing and local enrichment of the finite cell method with application to cemented granular materials
No full textIn recent times, immersed methods such as the finite cell method have been increasingly employed in structural mechanics to address complex-shaped problems. However, when dealing with heterogeneous microstructures, the FCM faces several challenges. Weak discontinuities occur at the interfaces between the different materials, resulting in kinks in the displacements and jumps in the strain and stress fields. Furthermore, the morphology of such composites is often described by 3D images, such as ones derived from X-ray computed tomography. These images lead to a non-smooth geometry description and thus, singularities in the stresses arise. In order to overcome these problems, several strategies are presented in this work. To capture the weak discontinuities at the material interfaces, the FCM is combined with local enrichment. Moreover, the L²-projection is extended and applied to heterogeneous microstructures, transforming the 3D images into smooth level-set functions. All of the proposed approaches are applied to numerical examples. Finally, an application of cemented granular material is investigated using three versions of the FCM and is verified against the finite element method. The results show that the proposed methods are suitable for simulating heterogeneous materials starting from CT scans.Deutsche Forschungsgemeinschaft (DFG