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Membrane processes are considered as comparably mild separation processes offering the potential for significant energy savings compared with azeotropic distillation processes. Despite higher investment and material costs, they are of particular interest for improving the energy efficiency in the chemical industry. However, energy savings of more than 20%–30% are rarely reported and even a general superiority can be disputed. To further elucidate this controversial, the current study pursues a quantitative assessment of the thermodynamic efficiency of pervaporation and vapor permeation processes with stand-alone distillation and hybrid membrane-assisted distillation processes for the separation of azeotropic mixtures. The results confirm the case-dependent potential of distillation processes to outperform membrane-assisted separations in terms of energy efficiency, considering proper heat integration. Although energy efficiency is becoming significantly important, it should be considered in the context of economic performance to determine an optimal trade-off and to select the best process alternative during conceptual process design.

Organoborane (OBs) sind vielseitige Intermediate für Anwendungen in der heutigen Landwirtschaft, Pharmazie und organischen Chemie. Um ihre umweltschädlichen und weniger selektiven chemischen Synthesen zu ersetzen, konzentrierte sich diese Arbeit auf den kürzlich entdeckten biokatalytischen Ansatz der OB-Synthese – biokatalytische Borylierung. Dabei wurde der Zustand der Substrate in Bezug auf pH-Wert, Temperatur und UV-Licht untersucht. Die Reaktion wurde kinetisch charakterisiert und ein mathematisches Modell abgeleitet, welches durch Simulationen bewertet wurde. Außerdem wurde die OB-Synthese im Batch-, Fed-Batch- und kontinuierlichen Betrieb durchgeführt, wobei insbesondere der Fed-Batch-Modus die Raum-Zeit-Ausbeute und die Endproduktkonzentration verbessert., Organoboranes (OBs) are versatile building blocks and precursors for various applications in todays agriculture, pharmacy and organic chemistry. To replace their environmentally offensive and less-selective chemical synthesis routes, this thesis focused on a recently discovered biocatalytic approach of OB synthesis called biocatalytic borylation. Here, tests investigated the state of the starting materials with respect to pH, temperature and UV-light. The enzymatic reaction was characterized according to Michaelis-Menten kinetics to derive a kinetic model, which was evaluated via simulations. Moreover, OB synthesis was executed in batch, fed-batch and continuous mode, where especially the fed-batch mode improved space-time yield and the final product concentration.

Sugar (fatty acid) esters are industrially relevant compounds, with a cumbersome production process due to the solubility issues of the substrates, which forces the use of environmentally unfriendly reaction media. Herein, deep eutectic solvents (DESs) are considered as a promising solution: several literature examples use glucose and different acyl donors to illustrate the efficient synthesis of sugar esters in classic DESs like choline chloride/urea (ChCl/U). However, this paper discloses that when sugars like lactose or other disaccharides are used, enzymes cannot efficiently perform (trans)esterifications in DESs, while the same reaction can proceed in mixtures like pyridine/tetrahydrofuran (Py/THF). This could be explained by computational solubility studies and molecular dynamics simulations of both reaction media, showing two effects: (i) on the one hand, large acyl donors (more than C10) display poor solubility in DESs and (ii) on the other hand, disaccharides interact with DES components. Thus, the DES affects the conformation of lactose (compared to the conformation observed in the Py/THF mixture), in such a way that the enzymatic reaction results impaired. Despite that classic DESs (e.g., ChCl/U) may not be useful for generalizing their use in saccharide ester syntheses, the achieved theoretical understanding of the reaction may enable the design of future DESs that can combine enzyme compatibility with eco-friendliness and efficiency in sugar chemistry.

Aerogels are nanoporous materials with high surface and very low thermal conductivity which present it as a promising candidate for thermal insulating materials [1]. The nanoscale porous structure is synthesized using supercritical CO2 drying (Sc-CO2) method which permits eliminating the solvent from the gel at zero surface tension without collapsing its structure [2], [3]. Specifically, Organic aerogels has an advantage over its inorganic counterparts mainly due to their higher mechanical stability [4]. Recently, there has been a driven interest to produce organic aerogels such as polyurethane aerogels from various biomass sources. [5] Lignin is one of the most investigated bio-based polyols for the production of polyurethane aerogels due to the abundance of hydroxyl groups in its aromatic structure [6]. However, the low solubility, low reactivity and high polydispersity emerge as challenges for the synthesis of lignin polyurethane aerogels [7].Thus, the resulting lignin polyurethane aerogels suffers from low surface area, high shrinkage and high thermal conductivity. This study aims on understanding the complexity lignin introduces into the synthesis of polyurethane aerogels with the goal of resolving the previously mentioned challenges. Preliminary studies showed the predominating factors to be lignin type, lignin-solvent interaction and monomer concertation. The experimental part focuses on understanding how these factors influences the gelation kinetics, morphology and structure evolution and crosslinking density. The results are further interpreted by measuring porosity, elemental analysis, volumetric shrinkage and thermal conductivity.

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This work aims to screen the extraction of oil and bioactive compounds including carotenes and tocochromanols from oil palm fruit with subcritical propane and without using a cosolvent. The overall extraction curves of palm oil with subcritical propane were studied and compared to those extracted with supercritical carbon dioxide. Carotenes and tocochromanols were evaluated not only in the extracted oil. but also in the oil of residual fiber in order to calculate the efficiency to recover these valuable compounds. The experimental results showed that oil yield of up to 70 % could be obtained within 120 minutes with subcritical propane at 50 bar and a flow rate of 35 kg·h-1·kg-1-. It was also shown that compressed propane is an excellent solvent for the extraction of oil enriched in carotenes and tocochromanols. Subcritical propane extraction can be used as an alternative process for the simultaneous recovery of these valuable minor components from palm fruit.

Sustainability research has increasingly emphasized the importance of value networks in the design and development of sustainable business models (SBM). This is because SBMs must incorporate economic, environmental and social goals to achieve their desired impacts, hence designing such models requires firms to develop an understanding of value creation from the perspective of all key stakeholders in their networks in order to co-create economic, social and ecological value. To advance our understanding of how value network activities shape SBM development, we conducted a longitudinal case study of RECUP, a born sustainable startup with a circular economy business model that has developed and worked with a broad value network to achieve a major reduction in waste from linear consumption. We identify three sets of value network activities that supported the continuous development of the firm’s value proposition and contributed to mutual value creation among stakeholders from business, politics and society: B2B-partnering, political agenda-setting and mobilizing end-consumers. Our contributions to research on SBM innovation and design include demonstrating how value network activities initially emerge through experimentation and consolidate over time through iterative learning processes. Such learning and adaption through dynamic value network activities is especially important, we argue, when value-creating factors are not sufficiently known in advance by startups and/or their stakeholders.

Consequently, a good mechanical design has to consider the user in his or her mechanical properties. The first part of this chapter deals with the discussion of the user as a mechanical load on the haptic device. The corresponding model is split into two independent elements depending on the frequency range of the oscillation. Methods and measurement setups for the derivation of mechanical impedance of the user are reviewed and a thorough analysis of impedance for different grip configurations is presented. In the second part of the chapter, the user is considered as the ultimate measure of quality for a haptic system. The relation of psychophysical parameters like the absolute threshold or the JND to engineering quality measures like resolution, errors and reproducibility is described and application depending quality measures like haptic transparency are introduced.

The development of modern mechatronic systems is often driven by the desire for more efficiency and accuracy. These requirements not only result in more complex system designs, but also in the simultaneous development of improved control strategies. Therefore, control of multibody systems is an active field of research. This contribution gives an overview of recent control-related research from the perspective of the multibody dynamics community. A literature review of the research activity in the journal Multibody System Dynamics is given. Afterwards, the framework of servo-constraints is reviewed, since it is a powerful tool for the computation of a feedforward controller and it is directly developed in the multibody system dynamics community. Thereby, solution strategies for all possible system types, such as differentially flat systems, minimum phase and non-minimum phase systems are discussed. Selected experimental and simulation results are shown to support the theoretical results.

Macroscopic strain experiments have revealed that silicon crystals traversed by parallel, channel-like nanopores functionalized with the artificial muscle polymer polypyrrole (PPy) exhibit large and reversible electrochemomechanical actuation in aqueous electrolytes. On a macroscopic scale these actuation properties are well understood. However, on the microscopical level this system still bears open questions, as to how the electrochemical expansion and contraction of PPy acts on to np-Si pore walls and how the collective motorics of the pore array emerges from the single-nanopore behavior. Here we present synchrotron-based, in operando x-ray diffraction on the evolving electrostrains in epilayers of this material grown on bulk silicon. An analysis of these experiments with micromechanical finite-element simulations, that are based on a full three-dimensional reconstruction of the nanoporous medium by transmission electron microscopy (TEM) tomography, shows that the in-plane mechanical response is dominantly isotropic despite the anisotropic elasticity of the single-crystalline host matrix. However, the structural anisotropy originating from the parallel alignment of the nanopores led to significant differences between the in- and out-of-plane electromechanical response. This response is not describable by a simple two-dimensional arrangement of parallel cylindrical channels. Rather, the simulations highlight that the dendritic shape of the silicon pore walls, including pore connections between the main channels, causes complex, highly inhomogeneous stress-strain fields in the crystalline host. Time-dependent x-ray scattering experiments on the dynamics of the actuator properties hint towards the importance of diffusion limitations, plastic deformation, and creep in the nanoconfined polymer upon (counter)ion adsorption and desorption, the very pore-scale processes causing the macroscopic electroactuation. From a more general perspective, our study demonstrates that

The paper presents a rigorous formulation of adjoint systems to be solved for a robust design optimization using the first-order second-moment method. This formulation allows to apply the method for any objective function, which is demonstrated by considering deformation at certain point and maximum stress as objectives subjected to random material stiffness and geometry, respectively. The presented approach requires the solution of at most three additional adjoint systems per uncertain system response, when compared to the deterministic case. Hence, the number of adjoint systems to be solved is independent of the number of random variables. This comes at the expense of accuracy, since the objective functions are assumed to be linear with respect to random parameters. However, the application to two standard cases and the validation with Monte Carlo simulations show that the approach is still able to find robust designs.

Information exchange via aeronautical data communication is of increasing importance for the communication between pilots and air traffic control, providing the basis for surveillance of aircraft in oceanic or remote airspaces, as well as enabling the communication between an airlines’ fleet and its operational control. The aeronautical data communication that is being transmitted via data link encompasses, among others, surveillance-related aircraft position updates, clearances for flight path change requests, maintenance-related status reports, estimated arrival times and weather information in accordance with the required performance, that is set by technical standards. Aeronautical data communication events are driven by an aircraft’s flight phase, the current airspace or may occur in a randomized manner throughout the flight. As the usage of aeronautical data communication is expected to grow in future, ample data link technologies are being evaluated and developed. The usability and operational value of new data link technologies for aeronautical applications can be evaluated by applying suitable models of the respective data link communication pattern combined with operational simulations. Current models for aeronautical data communication demand support the design and evaluation of direct aircraft-to-ground communication networks. The geographical location of the data communication demand is secondary for these models, since coverage areas can be defined, where direct communication links are available. New data link technologies offer the opportunity of direct data transfer between aircraft and forwarding of messages from sending aircraft to a ground entity via ad-hoc communication networks between aircraft. This is of special interest for the North Atlantic oceanic airspace, an airspace with high traffic density and little ground infrastructure, where communication currently relies mostly on satellite-based systems. For these airborne ad-hoc networks the de, Bundesministerium für Wirtschaft und Klimaschutz (BMWK)

Poröses Silizium ist ein äußerst vielseitiges Funktionsmaterial. In dieser Arbeit werden zwei verschiedene, von der Elektrochemie inspirierte Ansätze entwickelt und untersucht, um eine Aktuator-funktion in poröses Silizium zu integrieren. Der erste Ansatz zielt auf die Nutzung der elektrochemisch-mechanischen Kopplung an der Grenzfläche einer porösen Siliziumelektrode, die in eine wässrige Elektrolytlösung eingetaucht ist. Beim zweiten Ansatz wird das elektroaktive, elektrisch leitfähige Polymer Polypyrrol in die poröse Siliziumporenstruktur integriert, um ein Hybridmaterial zu schaffen. Beide Ansätze erzielen eine robuste und hoch reproduzierbare Aktuation, die dem angelegten Potential linear folgt und deren Arbeitsdichte mit klassischen Piezoaktoren vergleichbar ist., Porous silicon is highly versatile functional material. In this thesis two different electrochemistry-inspired approaches are developed and investigated to integrate an actuator functionality into porous silicon. The first approach aims to utilise electrochemo-mechanical coupling at the interface of a porous silicon electrode immersed in an aqueous electrolyte solution. The second approach comprises the integration of the electroactive, electrically conductive polymer polypyrrole into the porous silicon pore structure to create a hybrid material. Both approaches achieve a robust and highly reproducible actuation that follows the applied potential linear and whose work density compares well to classical piezo actuators.

One aspect in haptic devices is the design of the kinematics. The kinematics of a mechanism is the key to implement and accomplish the design goals, like transmitting dynamic feedback in the form of forces or torques, or allowing a sufficient workspace for the user to interact with environment. This chapter introduces the steps of the kinematic design. The chapter consists of five main sections. The first section gives an overview on some basic definitions and the main types of mechanisms. In the second section, the first step in the design, defining the structure of the mechanism, is introduced. This is accompanied with an example. After choosing the most applicable structure for the desired application, the second step takes place, where the kinematic equations are solved. These equations are used to describe the relation between the operating point of the mechanism and the base at any point in time. Different approaches are used to solve those equations depending on the type of the mechanism used. The third and final step in the design process is introduced in the fourth section. This step contains the optimization process of the mechanism in order to achieve a desired operation of the mechanism. Last but not least, the importance of modeling and simulation is discussed in the last section.

Sustainable aviation fuels (SAF) can already be produced today from various biogenic and non-biogenic feedstocks by biochemical or thermochemical processes or a combination of these. In contrast to non-biogenic fuels, biogenically produced fuels and energy carriers are already being produced today in large quantities and used as an energy source. In addition to hydrogenated ester and fatty acid (HEFA)-based SAF, these include biogas and bioethanol, which are used today in particular in heat generation, electricity generation or road transport. In addition, there are other biogenically produced intermediates, such as 2,3-butanediol, which can be used to produce an SAF. Against this background, a comparison of different SAF production routes based on the current industrially available products biogas and bioethanol, as well as a possible production of 2,3-butanediol to SAF with technical key figures will be evaluated against each other. The goal is to focus on processes with a maximization of the carbon yield without considering CO2 reduction with hydrogen and thus a combined biological and non-biological process. Thus, the installation of large amounts of renewable power generation is not required explicitly for SAF production and a potentially faster availability of larger SAF quantities could be achieved. To achieve this goal, the first processes are designed on the basis of a detailed literature research and evaluated with regard to their carbon efficiency. In the process route based on biogas as feedstock, carbon activation must first be achieved by reformation. The resulting synthesis gas can be further processed via the methanol or the Fischer-Tropsch pathway. Since the methanol intermediate is already available on an industrial scale - albeit from fossil sources - the methanol process route is considered, since this results in an independence of the various process steps. The alcohol-to-jet process designs and concepts are then analyzed for the ethanol and for, European Union

There exist several discretization techniques for the numerical solution of partial differential equations. In addition to classical finite difference, finite element and finite volume techniques, a more recent approach employs radial basis functions to generate differentiation stencils on unstructured point sets. This approach, abbreviated by RBF-FD (radial basis function-finite difference), has gained in popularity since it enjoys several advantages: It is (relatively) straightforward, does not require a mesh and generalizes easily to higher spatial dimensions. However, its application is not quite as blackbox as it may appear at first sight. The computed solution might suffer severely from various sources of errors if RBF-FD parameters are not selected carefully. Through comprehensive numerical experiments, we study the influence of several of these parameters on the condition numbers of intermediate (local) weight matrices, on the condition number of the resulting (global) stiffness matrix and ultimately on the approximation error of the computed discrete solution to the partial differential equation. The parameters of investigation include the type of RBF (and its shape or other parameters if applicable), the degree of polynomial augmentation, the discretization stencil size, the underlying type of point set (structured/unstructured), and the total number of (interior and boundary) points to discretize the PDE, here chosen as a three-dimensional Poisson’s problem with Dirichlet boundary conditions. Numerical tests on a sphere as well as tests for the convection-diffusion equation are included in a supplement and demonstrate that the results obtained for the Laplace problem on a cube generalize to wider problem classes. The purpose of this paper is to provide a comprehensive survey on the various components of the basic algorithms for RBF-FD discretization and steer away from potential pitfalls such as computationally more expensive setups which not always lead

Biowaste management has a large potential for supporting closed-loop resource and nutrient management. The exploitation of this potential, however, is affected by upstream determinants, such as the consumers’ behavior (separation efficiency), which influence the quantity and quality of biowaste intended for valorization. The goal of this study is to determine the effect of these upstream determinants on the environmental and the economic performance of biowaste management, upon implementation of an improved socio-technical collection infrastructure. Interventions were performed in two areas (A and B) in a Northern German city. The methodologies used for the environmental and the economic evaluation are the life cycle assessment and the net present value analysis, respectively. The functional unit of 1 kt of waste (biowaste and residual waste) generated at households was used. Three scenarios are assessed for each area and reflect the before (Ab, Bb), during (Ad, Bd), and after (Aa, Ba) phases of these interventions. The average global warming mitigation potential for Ab and Bb was − 8, for Ad and Bd was − 56, and for Aa and Ba was − 22 kg CO2 eq·kt−1 biowaste. The economic assessment showed that the improved collection system is economically beneficial due to the larger amount of valuable products and lower overall treatment costs. The results suggest that improved sorting can influence the environmental and economic performance of the studied system and both study areas present environmental impact mitigation during the monitoring period. However, our results suggest sustained awareness-raising activities in order to maintain a high efficiency in household waste sorting., European Union

This paper presents a novel method for online tool recognition in manual assembly processes. The goal was to develop and implement a method that can be integrated with existing Human Action Recognition (HAR) methods in collaborative tasks. We examined the state-of-the-art for progress detection in manual assembly via HAR-based methods, as well as visual tool-recognition approaches. A novel online tool-recognition pipeline for handheld tools is introduced, utilizing a two-stage approach. First, a Region Of Interest (ROI) was extracted by determining the wrist position using skeletal data. Afterward, this ROI was cropped, and the tool located within this ROI was classified. This pipeline enabled several algorithms for object recognition and demonstrated the generalizability of our approach. An extensive training dataset for tool-recognition purposes is presented, which was evaluated with two image-classification approaches. An offline pipeline evaluation was performed with twelve tool classes. Additionally, various online tests were conducted covering different aspects of this vision application, such as two assembly scenarios, unknown instances of known classes, as well as challenging backgrounds. The introduced pipeline was competitive with other approaches regarding prediction accuracy, robustness, diversity, extendability/flexibility, and online capability.

Renewably sourced aviation fuels (“SAF”) can reduce GHG emissions by 50 %-90 % on a lifecycle basis. However, the aviation-induced climate impact is only partially caused by GHG emissions, a significant fraction can be attributed to contrail formation and NOx emissions, amongst others. The formation of contrails is substantially influenced by soot formation during combustion. It has been demonstrated that an increased hydrogen content, e.g., by using SAF or hydroprocessed fossil-based kerosene, can reduce soot formation. Studies have shown that between 2 % and 10 % of the flights cause almost 80 % of the contrail energy forcing. However, the market share of renewably sourced aviation fuels is presently far below 1 %, and requirements for hydroprocessing of fossil-based kerosene do not exist. Against this background, using “low-soot” fuels exclusively where contrails form appears promising. However, this would require dedicated fuel supply chains, e.g., to accommodate two different fuel types at one airport. This study aims to assess the techno-economical feasibility of such concepts. Fuel production costs are derived for varying degrees of hydroprocessing severity and all major SAF production pathways, such as HEFA-SPK, FT-SPK, and AtJ-SPK. Fuel allocation concepts are assessed from a uniform distribution towards a dedicated use on particular flight segments by estimating associated costs and potential durations for their implementation. In comparison with market-ramp-up scenarios for such “low-soot fuels”, the mitigation potential of various fuel allocation concepts is discussed. Hereby, this study aims to contribute towards the design of measures to effectively and swiftly reduce the overall climate impact of aviation.

It is important to know the mean time until critical roll motion occurs in various operating and sea conditions, in order to determine and ensure the safety of ship designs and operating ships. Since typical ocean waves are irregular, the forcing and roll response of the ship is considered to be a stochastic process of colored noise type. However, the simulation of the corresponding first passage times is very time consuming. Therefore, an approach for the determination of mean first passage times of critical roll motion of ships is proposed in this paper which needs much less computation time. This approach is based on explicit formulas for the roll energy of the ship. These formulas are used to determine the mean first passage times based on integral expressions, which were previously obtained. The resulting integral expressions can be computed very fast using standard quadrature formulas. Moreover, the underlying model for ship dynamics is extended by introducing a new effective wave for short-crested sea states. This is an extension to the improved Grim's effective wave concept.

We present a hydrodynamic and structural model to design a single foil wave cycloidal rotor in regular waves. The hydrodynamic part considers potential flow and represents the foil as a point vortex. Unsteady effects are accounted for through Theodorsen's function. The structural part utilises beam theory to compute the bending moments and stresses on the foil of the cyclorotor. The validity of the hydrodynamic model is explored with the aid of CFD, and the CFD results are bench marked versus experimental measurements. Results show that the hydrodynamic model estimates the mean radial loading on the foil within 20%–25% in attached flow conditions, whilst it is accurate to predict the mean tangential loading only when operating close to stall, at maximum lift conditions. Because the optimal structural operation of the rotor is in attached flow conditions, and close to stall, we utilise the coupled model to design a rotor that operates optimally for a range of different sea conditions. We find that with careful dimensioning of the radius and span, power extraction in regular waves can be optimised, whilst the structural penalty is kept constant at the allowable stress level.

We introduce a novel ultra-low power system for tracking animal movements over long periods with an unprecedented high-temporal-resolution. The localization principle is based on the detection of cellular base stations using a miniaturized software-defined radio, weighing 2.0 g, including the battery, and having a size equivalent to two stacked 1-euro cent coins. Therefore, the system is small and lightweight enough to be deployed on small, wide-ranging, or migrating animals, such as European bats, for movement analysis with an unprecedented spatiotemporal resolution. The position estimation relies on a post-processing probabilistic RF pattern-matching method based on the acquired base stations and power levels. In several field tests, the system has been successfully verified, and a run-time of close to one year has been demonstrated., We introduce a novel ultra-low power system for tracking animal movements over long periods with an unprecedented high-temporal-resolution. The localization principle is based on the detection of cellular base stations using a miniaturized software-defined radio, weighing 2.0 g, including the battery, and having a size equivalent to two stacked 1-euro cent coins. Therefore, the system is small and lightweight enough to be deployed on small, wide-ranging, or migrating animals, such as European bats, for movement analysis with an unprecedented spatiotemporal resolution. The position estimation relies on a post-processing probabilistic RF pattern-matching method based on the acquired base stations and power levels. In several field tests, the system has been successfully verified, and a run-time of close to one year has been demonstrated.

Hydrophobic soils have natural or artificial origin. In this context, some techniques exist to turn into hydrophobic sand that was originally hydrophilic, as most soils in fact are. Its classical application is impermeabilizing structures where water percolation is not desired. In this paper, a new technique to achieve hydrophobicity is described. It consists of coating particles via cold plasma. The process is known to the industry, but its application in geotechnics is not yet described in literature. The monomers used were octafluorcyclobutane (C4F8) and 1H,1H,2H,2H-perfluoroctylacrilate (PFA-C6). For each monomer, the material was in the coating chamber during two different time spans and a sample was pretreated with oxygen. Different mechanical, thermal and hydraulic conditions were imposed to the samples in order to evaluate the resistance of the coating and its properties. The hydrophobicity was evaluated by means of Water Drop Penetration Time. Results indicate that longer time spans in the cold plasma chamber lead to a more hydrophobic material and that oxygen pretreatment on the sample is irrelevant. It was also observed that mechanical, hydraulic and thermal procedures influence the coating. These observations lead to optimization of the production process and to the understanding of how the material can be applied in the construction industry and what mechanical/hydraulic loads it can be subjected to.

Supercrystalline nanocomposites (SCNCs) are inorganic-organic hybrid materials with a unique periodic nanostructure, and thus they have been gaining growing attention for their intriguing functional properties and parallelisms with hierarchical biomaterials. Their mechanical behavior remains, however, poorly understood, even though its understanding and control are important to allow SCNCs’ implementation into devices. An important aspect that has not been tackled yet is their time-dependent deformation behavior, which is nevertheless expected to play an important role in materials containing such a distribution of organic phase. Hereby, we report on the creep of ceramic-organic SCNCs with varying degrees of organic crosslinking, as assessed via nanoindentation. Creep strains and their partial recoverability are observed, hinting at the co-presence of viscoelasticity and viscoplasticity, and a clear effect of crosslinking in decreasing the overall material deformability emerges. We rationalize our experimental observations with the analysis of stress exponent and activation volume, resulting in a power-law breakdown behavior and governing deformation mechanisms occurring at the organic sub-nm interfaces scale, as rearrangement of organic ligands. The set of results is reinforced by the evaluation of the strain rate sensitivity via strain rate jump tests, and the assessment of the effect of oscillations during continuous stiffness measurement mode.

This paper presents a comprehensive experimental study on the effect of extreme waves on a LNG carrier. The LNG carrier model was equipped with a variety of sensors to measure motions, green water height on deck as well as local and global loads. Experiments in transient wave packets provided the general performance in waves in terms of response amplitude operators and were accompanied by tests in regular waves with two different wave steepness. These tests allowed detailed insights into the nonlinear behavior of the vertical wave bending moment in steep waves showing that green water on deck can contribute to a decrease of vertical wave bending moment. Afterwards, systematic model tests in irregular waves were performed to provide the basis for statistical analysis. It is shown that the generalized extreme value distribution model is suitable for the estimation of the extreme peak values of motions and loads. Finally, model tests in tailored extreme wave sequences were conducted comparing the results with the statistical analysis. For this purpose, analytical breather solutions of the nonlinear Schrödinger equation were applied to generate tailored extreme waves of certain critical wave lengths in terms of ship response. Besides these design extreme waves, the LGN carrier was also investigated in the model scale reproduction of the real-world Draupner wave. By comparing the motions, vertical wave bending moment, green water column and slamming pressures it is concluded that the breather solutions are a powerful and efficient tool for the generation of design extreme waves of certain critical wave lengths for wave/structure investigations on different subjects.

Geometry conforming meshing techniques such as the finite element method (FEM) face a big challenge when dealing with complex and heterogeneous microstructures. Therefore, efficient simulation methods are needed combining accurate morphological reproducibility and computational efficiency. For such problems, the finite cell method (FCM) is a promising approach, which uses a Cartesian grid – independent of the geometry – leading to a fast and efficient mesh generation. However, to handle complex microstructures such as cemented sands the FCM is not sufficient anymore. Therefore, three different versions of the FCM are presented: first, the FCM, which is directly applied to CT scans (denoted as “VoxelFCM”). Second, the FCM combined with a global L² -projection, leading to a smooth geometry description (denoted as “FCM”). And finally, the FCM with L² -projection, which is extended by a local enrichment to capture weak discontinuities at the interfaces between the different phases (denoted as “FCM-Enrichment”). First, in a numerical study, the different versions of the FCM are investigated. Then, these methods are verified against the FEM. Finally, these methods are used to gain a deeper insight into the micromechanical phenomena of cemented sands under compressive loading., Deutsche Forschungsgemeinschaft (DFG)

We describe the background, features and functions of a custom application for the acquisition, live presentation, and convenient recording of ballistocardiography data acquired by external accelerometric sensors.

Adherent cells, mammalian or human, are ubiquitous for production of viral vaccines, in gene therapy and in immuno-oncology. The development of a cell-expansion process with adherent cells is challenging as scale-up requires the expansion of the cell culture surface. Microcarrier (MC)-based cultures are still predominate. However, the development of MC processes from scratch possesses particular challenges due to their complexity. A novel approach for the reduction of development times and costs of cell propagation processes is the combination of mathematical process models with statistical optimization methods, called model-assisted Design of Experiments (mDoE). In this study, an mDoE workflow was evaluated successfully for the design of a MC-based expansion process of adherent L929 cells at a very early stage of development with limited prior knowledge. At the start, the analytical methods and the screening of appropriate MCs were evaluated. Then, cause-effect relationships (e.g., cell growth related to medium conditions) were worked out, and a mathematical process model was set-up and adapted to experimental data for modeling purposes. The model was subsequently used in mDoE to identify optimized process conditions, which were proven experimentally. An eight-fold increase in cell yield was achieved basically by reducing the initial MC concentration.

We explore the potential for predicting indoor photovoltaic energy on a forecasting horizon of up to 24 hours. The objective is to enable energy management approaches that exploit harvesting opportunities more strategically, for which they require more accurate energy intake predictions. Our study is based on a data set covering over 3 years, for which we simulate online machine learning algorithms with different amounts of training data and input features. Our results show that relatively simple machine learning methods can outperform a persistent predictor considerably, and we observed a reduction of errors of up to 56%. When devices obtain a significant amount of sunlight, adding the weather forecast improves the prediction accuracy. We discuss prediction features, the amount of training data and analyze the sources of errors to understand the potential of indoor photovoltaic energy harvesting predictions.

In dieser Arbeit wird ein aktives 16 × 1-Modul für phasengesteuerte Gruppenstrahler im K/Ka-Band vorgestellt. Das Modul beruht auf substratintegrierten Wellenleiterantennen in Kombination mit kommerziellen rauscharmen Verstärkern, Strahlformerchips und Mischern. Es unterstützt den Vollduplex-Betrieb für zwei Polarisationen, nämlich die linkszirkulare und die rechtszirkulare. Die benötigten Systemkomponenten und -netzwerke werden ermittelt, ausgelegt, entworfen, hergestellt und vermessen. Die Netzwerke werden mit den Elementarstrahlern zu dem aktiven Antennenmodul kombiniert, das anschließend hergestellt und in einer Antennenmesskammer vermessen wird., This work presents a 16 × 1 active module for phased array antennas at K/Ka-Band. The module relies on substrate integrated waveguide antennas in combination with commercial low noise amplifiers, beamformer chips, and mixers. It supports full-duplex operation for both left and right handed circular polarization. The required system components and networks are identified, laid out, designed, fabricated, and measured. They are combined with the antennas to yield the desired active module, which is then fabricated and experimentally characterized in an anechoic chamber., Deutsches Zentrum für Luft- und Raumfahrt (DLR)

Vergleichende Betrachtung von Ammoniak und Methanol in Hinblick auf die aktuelle Nutzung, produktionstechnische, ökonomische und ökologische Aspekte sowie anwendungsseitige Aspekte., Comparative consideration of ammonia and methanol with regard to current use, production technology, economic and environmental aspects, and application aspects.

In dieser Arbeit wird ein neuer Ansatz zur kooperativen Lösung des Source Seeking Problems vorgestellt, der auf Methoden der Formationsregelung beruht. Zwei Arten der Formationsregelung - verschiebungsbasiert und entfernungsbasiert - werden dafür untersucht und für verschiedene Agentenmodelle angepasst. Die Stabilität der vorgeschlagenen Verfahren wird durch eine Lyapunov Stabilitätsanalyse gezeigt. Simulationsstudien demonstrieren die Leistungsfähigkeit der Methode. Eine experimentelle Validierung erfolgte durch Implementierung einer entfernungsbasierten Formationsregelung für Source Seeking auf einer Gruppe zweirädriger Roboter., This thesis proposes a novel approach to the problem of cooperative source seeking based on formation control. Two types of formation control - displacement based and distance based - are considered and adapted to different agent models. A Lyapunov stability analysis of the proposed approach is given. The practicality of the method is demonstrated in simulation studies. In addition, the method has been validated experimentally by implementing a distance-based formation control scheme for source seeking by a group of wheeled robots.

With continuing evolution of imaging techniques from medical applications and materials science, non-destructive imaging experiments have also become an important method to investigate soil specimens. Amongst other methods, computed tomography (CT) has developed to a tool to visualise and better understand the microstructure of different soils based on 3D image data. Furthermore, the acquisition of a temporal series of CT images allows to study processes in soils on the microscale, e. g., during mechanical loading. In order to study the hydraulic and mechanical behaviour of unsaturated granular soils, we combine different custom-built miniaturised experimental set-ups with geomechanics background with computed tomography, yielding so-called in situ CT experiments. By means of image reconstruction and further image analysis based on segmented CT images acquired during different hydraulic and mechanical experiments, we study the drainage and imbibition process as well as the shear process of unsaturated sand and glass bead specimens on the pore or grain scale. The analysis of data on the microscopic level, including the phase distribution, interfacial areas, contact lines as well as radii of curvature of capillary menisci, allows to obtain insights into the macroscopic water retention behaviour and shear behaviour of granular soils.

It can be considered that electric generating power from solar energy is an essential topic in the energy field. Several environmental factors affect the energy production of solar cells. Dust accumulation is one of the main factors which significantly negatively influences output energy. However, this topic is not investigated extensively, despite its significant impact, especially in arid areas such as Iraq. In this research paper, both theoretical and experimental techniques were applied to investigate the effect of accumulated dust particles on the efficiency of photovoltaic PV systems. An on-grid photovoltaic system was selected to achieve the experimental work. The results proved the negative effect of dust particles on the performance of the solar cell. Based on the obtained results, a new relationship was introduced between efficiency degradation and the amount of dust that accumulated on the surfaces of cells. This correlation is considered a necessity to find the characteristics of PV solar systems to improve their performance and efficiency. The new correlation introduced in this paper can be considered a promising prediction tool to estimate the characteristics of photovoltaic solar cells under different actual environment working conditions. The output power of the cleaned array system increased by 5–26% compared with the untreated system over the test period. Furthermore, the performance ratio (PR) was enhanced within the cleaned array system by 3 to 6 compared with the uncleaned array. A significant formula introduced the connection between the actual output power of the PV systems and the environmental condition (dust accumulation), where it can be considered as feedback to keep the performance in a steady status, which means obtaining the highest output power.

In dem letzten Jahrzehnt sind diverse industrielle Bioraffinerien in Betrieb gegangen, welche eine Vorbehandlung von Lignozellulose als zentralen Aufschlussschritt nutzen. Dabei ist das Ziel, möglichst kosteneffizient Zellulose-Ethanol herzustellen, welcher die Zellulose, manchmal auch Teile der Hemizellulose verwendet. Andere Rohstoffbestandteile der nicht-essbaren Biomasse können hier nur als Nebenprodukte einer geringen Wertschöpfung zugeführt werden, da die Qualität sehr niedrig ist. Für einen Wandel von fossilen zu nachwachsenden Rohstoffen in der chemischen Industrie bedarf es neuen Verfahren, welche es kosteneffizient ermöglichen, alle Lignozellulose-Bestandteile in hoher Qualität bereitzustellen. Solche Vollfraktionierungs-Prozesse für widerstandsfähige Biomassen werden aktuell entwickelt, jedoch ist die Raffination entweder kostengünstig oder vollständig. Der entscheidende Schritt ist die Hydrolyse der Hemicellulose. Schon bei unzureichendem Umsatz des Biopolymers reagiert das entstandene Produkt (wasserlösliche Pentosen) zu Furfural und weiteren Störstoffen ab. Der Durchströmungsreaktor beispielsweise nutzt eine in-situ Produkt-Abtrennung zur Verbesserung der Ausbeute; dieses gelingt allerdings nur bei sehr hohem Einsatz von heißem Wasser und damit Energie und Kosten. In dieser Arbeit wird ein zweistufiger Aufschluss einjähriger Lignozellulose entwickelt und experimentell validiert. Dabei wird die Hemizellulose-Hydrolyse gestoppt, wenn es gerade noch nicht zu einer Produkt-Degradierung kommt. Dieses ist beim Maximum der Produkt-Konzentration der Fall. Das Produkt wird anschließend mit Wasser atmosphärisch extrahiert und kann somit nicht weiter abreagieren. In dem zweiten Schritt wird die Produktausbeute weiter über das ursprüngliche Maximum erhöht. Die Kinetik des Reaktionskonzeptes wurde mit einer Heißwasserhydrolyse untersucht und auf ein Reaktorkonzept übertragen, welches mit einer Direktinjektion von Sattdampf arbeitet. Eine umfangreiche Untersuchung d, In the last decade, several factories were put into operation that used the pretreatment of lignocellulose as a central refining stage, mainly to convert cellulose, sometimes also a fraction of hemicellulose, to lignocellulosic ethanol. The focus is on cheap lignocellulosic ethanol; thus, other parts of the non-edible biomass are turned to low-value applications due to low quality. The potential of hemicellulose and lignin remains vastly untapped. To shift the feedstock of the chemical industry to renewable resources, it is required for all compounds of lignocellulose to be refined in high quality so that they can be used for the production of chemicals. Such full-fractionation processes are under development but fail to deconstruct the recalcitrant biomass efficiently. A critical challenge is the hydrolysis of hemicellulose. Before the conversion of the polymer is sufficiently high, the formed products (water-soluble pentose) decay to unwanted, harmful, and reactive degradation products like furfural. Reactors with in-situ product removal allow a full-fractionation under the conditions of excessive water and energy consumption, which is economically not feasible. In this work, a two-step pretreatment is proposed and investigated experimentally. The hemicellulose conversion is stopped before the degradations take place to extract the desired product at its peak concentration. In the second step, the hemicellulose conversion is continued to the required level. The kinetic of this concept was investigated in Liquid Hot Water reactors and transferred to steam pretreatment reactors. A rigorous mass balance approves the high separation yields and avoidance of degradation products. The resulting (intermediate) products, oligomer xylan, glucose, and solid lignin, were tested in relevant applications to conclude the high quality of the products. Finally, critical steps are validated in continuous steam pretreatment reactors to allow the scaling of the process to an industri

Mit Einführung des fahrerlosen Fahrens wird sich das Logistiksystem verändern. Die Wirkungen sind in der bestehenden Literatur bislang jedoch wenig diskutiert. Die Arbeit analysiert die Wirkungen des fahrerlosen Fahrens im Logistiksystem und ermittelt mögliche Rückkopplungsschleifen. Die Ergebnisse basieren auf einer Literaturanalyse und einem dreistufigen Modellansatz, der die Wirkungen sowohl qualifiziert als auch quantifiziert und die Ableitung von Gestaltungsoptionen zulässt, mit denen die relevanten Akteure unerwünschte Wirkungen reduzieren können., The driverless driving will change the logistics system in the future. These changes are little discussed in the existing literature so far. This work helps to understand the effects of driverless driving in the logistics system. The findings are based on a literature review and a three-stage model approach, which qualifies the effects as well as quantifies them and allows the derivation of design options, which can be used by the relevant actors to reduce undesirable effects.

Die additive Fertigung hat in den letzten Jahren großes Interesse geweckt, da sie einige Vorteile gegenüber herkömmlichen Fertigungsverfahren aufweist. Trotz des Potenzials sind viele Anwendungen aufgrund von Zuverlässigkeitsproblemen und einer begrenzten Materialauswahl immer noch auf das Rapid Prototyping beschränkt. Diese wissenschaftliche Studie zeigt zwei Anwendungen, die über das Rapid Prototyping hinausgehen und dabei strukturelle und funktionelle Materialien verwenden. Zuerst wird ein probabilistischer Prozess für den Leichtbau mit Gitterstrukturen vorgeschlagen. Zweitens wird eine Materialformulierung entwickelt, die das Anisotropie-Problem der Schmelzschichtung löst und Funktionsintegration durch elektrische Leitfähigkeit sowie Temperatur- und Dehnungsmessung ermöglicht., Additive manufacturing has attracted great interest in recent years as it shows several advantages over conventional manufacturing techniques. Despite its potential, many applications are still limited to rapid prototyping due to reliability issues and a limited material choice. This study shows two applications that go beyond rapid prototyping using structural and functional materials. First, a probabilistic process for lightweight design with lattice structures is proposed. Second, a new material formulation is developed that solves the anisotropy issue of fused filament fabrication and allows functional integration by electrical conductivity as well as temperature and strain sensing.

Personenorientierte Komfortsysteme zur sommerlichen Kühlung, die das konditionierte Luftvolumen auf einzelne Körperteile oder Wirkbereiche des Nutzers reduzieren, werden untersucht. Die Verwendung von Phasenwechselmaterialien ermöglicht eine Kühlung ohne Kältemaschine. Das entwickelte Kühlelement beschränkt die Kühlung auf Hände und Torso des Nutzers. Bei einer maximalen elektrischen Leistung von 1,3 W wird über einen Zeitraum von drei Stunden bei einer Raumtemperatur von 27 °C eine durchschnittliche Temperaturdifferenz von 2,2 K über das Kühlelement erreicht. Die Kühlleistung beträgt 18,5 W bei einem COP von 18,12. Neben der energetischen Bewertung wird der positive Einfluss des Kühlelements auf den thermischen Komfort in einer Feldstudie mit zehn Teilnehmern anhand von Fragebögen bestätigt., Personal comfort systems, which reduce the conditioned air volume to individual body parts or effective areas of the user, for summer cooling are being investigated. The use of phase change materials allows cooling without a chiller. The developed cooling element limits cooling to the user's hands and torso. With a maximum electrical power requirement of 1.3 W, an average temperature difference of 2.2 K can be achieved over a period of three hours at a room temperature of 27 °C via the cooling element. The cooling capacity is 18.5 W with a COP of 18.12. In addition to the energy evaluation, the positive influence of the phase change material cooling element on thermal comfort is confirmed in a field study with ten participants using questionnaires.

The monitoring of vital signs and increasing patient comfort are cornerstones of modern neonatal intensive care. Commonly used monitoring methods are based on skin contact which can cause irritations and discomfort in preterm neonates. Therefore, non-contact approaches are the subject of current research aiming to resolve this dichotomy. Robust neonatal face detection is essential for the reliable detection of heart rate, respiratory rate and body temperature. While solutions for adult face detection are established, the unique neonatal proportions require a tailored approach. Additionally, sufficient open-source data of neonates on the NICU is lacking. We set out to train neural networks with the thermal-RGB-fusion data of neonates. We propose a novel indirect fusion approach including the sensor fusion of a thermal and RGB camera based on a 3D time-of-flight (ToF) camera. Unlike other approaches, this method is tailored for close distances encountered in neonatal incubators. Two neural networks were used with the fusion data and compared to RGB and thermal networks. For the class “head” we reached average precision values of 0.9958 (RetinaNet) and 0.9455 (YOLOv3) for the fusion data. Compared with the literature, similar precision was achieved, but we are the first to train a neural network with fusion data of neonates. The advantage of this approach is in calculating the detection area directly from the fusion image for the RGB and thermal modality. This increases data efficiency by 66%. Our results will facilitate the future development of non-contact monitoring to further improve the standard of care for preterm neonates., The monitoring of vital signs and increasing patient comfort are cornerstones of modern neonatal intensive care. Commonly used monitoring methods are based on skin contact which can cause irritations and discomfort in preterm neonates. Therefore, non-contact approaches are the subject of current research aiming to resolve this dichotomy. Robust neonatal face detection is essential for the reliable detection of heart rate, respiratory rate and body temperature. While solutions for adult face detection are established, the unique neonatal proportions require a tailored approach. Additionally, sufficient open-source data of neonates on the NICU is lacking. We set out to train neural networks with the thermal-RGB-fusion data of neonates. We propose a novel indirect fusion approach including the sensor fusion of a thermal and RGB camera based on a 3D time-of-flight (ToF) camera. Unlike other approaches, this method is tailored for close distances encountered in neonatal incubators. Two neural networks were used with the fusion data and compared to RGB and thermal networks. For the class “head” we reached average precision values of 0.9958 (RetinaNet) and 0.9455 (YOLOv3) for the fusion data. Compared with the literature, similar precision was achieved, but we are the first to train a neural network with fusion data of neonates. The advantage of this approach is in calculating the detection area directly from the fusion image for the RGB and thermal modality. This increases data efficiency by 66%. Our results will facilitate the future development of non-contact monitoring to further improve the standard of care for preterm neonates., Bundesministerium für Bildung und Forschung (BMBF)

The mechanical characterisation of cables can help improving the production and lifetime of various products, for example a robotic arm. Cables however form a class of composite structures, that is highly anisotropic and dissipates energy due to the reorientation of its constituents which is superimposed by the dissipation due to the deformation of the polymer components. Cables also have a degree of randomness in their structure. Moreover, the stiffness in one loading direction is coupled to the stiffness in another loading direction. In this work, experimental investigations on the mechanical properties of the cables are presented. An experimental setup has been constructed to test the cables in tensile, torsion and the bending directions individually as well as coupled to each other. Free bending tests were conducted where axial forces were compensated during the bending to dissociate the tensile and the bending properties of the cables. To apply larger tensile and torsional loads on cables a commercial testing device was also used. To characterise the influence of bending on torsion, free bending tests were conducted with a combination of torsional load. Thus, a complete mechanical characterisation of a cable is presented., Deutsche Forschungsgemeinschaft (DFG)

From the aspect of traffic safety, the brake system is one of the most important systems. For all exploitation conditions, for which vehicles are projected, and for loads in prescribed boundaries, no matter to the vehicle speed, it is important, for the brake system to be reliable and to provide a very fast stop, or speed adjustment to road conditions. During the stop or during the speed adjustment it comes to the disc brakes temperature increment. So, because of this, the experimental investigations were conducted, in order to determine final values of the temperature for multiple braking processes until stop. In this paper, were conducted two experimental tests for the same vehicle, but for different speeds, which were 60 km/h and 80 km/h, while the other parameters (initial temperature, the mass of the simulated vehicle, number of repetitions) were the same for both tests. The conclusion is that by increment of the speed, rises the necessary time to stop the simulated vehicle, and by this, rises and the stopping distance. Also, rises and the temperature of the disc brake, with the increment of the vehicle speed., Republic of Serbia, Ministry of Education, Science and Technological Development

Magnetic Particle Imaging hardware has reached human scale and thus patient safety questions and clinical application scenarios are in the focus of current research. In this work, we present a safe real-time 3D MPI system for cerebral applications. High voltages are avoided to ensure patient safety by a low voltage-high current transmit coil design. The developed 2D drive-field generator generates a field-free-point trajectory in the sagittal xz-plane that is shifted with low frequency by a dynamic selection-field sequence along the y-axis. The scanner generates 3D images with 4 frames/second and allows for direct visualization of the clinically preferred transversal yz-plane, which is crucial for future brain examinations. Advanced reconstruction techniques reach a system sensitivity of 4 µgFe with respect to the iron mass in a sensitivity study., Deutsche Forschungsgemeinschaft (DFG)

Underwater radiated noise is part of the anthropogenic emissions into the environment and as such a pressing problem for the preservation of the marine ecosystem. In order to direct attention to the most relevant noise sources associated with ships it is crucial to precisely determine the local origins of the acoustic emissions. As acoustics are by nature perceived through a very subjective auditory perception, visual post-processing support is required in engineering applications to assess the impact on structures and to create an understanding of the overall noise field geometrically, topologically, and directionally. In the context of CFD simulations, this may be achieved by considering the pressure pulses on domain boundary surfaces or passive surfaces, or by evaluating various volumetric information, such as Proudman acoustic sources or the Lighthill stress tensor, which is the fundamental input for many acoustic analogies including the Ffowcs-Williams-Hawkings method. For a propeller-hull configuration, the acoustic emissions from modeled and scale-resolved turbulence two-phase CFD analyses are evaluated in detail with different visualization methods. It is shown that the spatial distribution information of frequency domain pressure pulses, and the corresponding complex phase angles on specific passive geometries, as well as the Lighthill stress tensor may be utilized to create a better understanding of underwater acoustics. This allows the identification of source types and their respective excitation of the hull and emission characteristics of the hydrodynamic sources into the fluid domain, as well as the effect of the CFD simulation domain geometry extent., Underwater radiated noise is part of the anthropogenic emissions into the environment and as such a pressing problem for the preservation of the marine ecosystem. In order to direct attention to the most relevant noise sources associated with ships it is crucial to precisely determine the local origins of the acoustic emissions. As acoustics are by nature perceived through a very subjective auditory perception, visual post-processing support is required in engineering applications to assess the impact on structures and to create an understanding of the overall noise field geometrically, topologically, and directionally. In the context of CFD simulations, this may be achieved by considering the pressure pulses on domain boundary surfaces or passive surfaces, or by evaluating various volumetric information, such as Proudman acoustic sources or the Lighthill stress tensor, which is the fundamental input for many acoustic analogies including the Ffowcs-Williams-Hawkings method. For a propeller-hull configuration, the acoustic emissions from modeled and scale-resolved turbulence two-phase CFD analyses are evaluated in detail with different visualization methods. It is shown that the spatial distribution information of frequency domain pressure pulses, and the corresponding complex phase angles on specific passive geometries, as well as the Lighthill stress tensor may be utilized to create a better understanding of underwater acoustics. This allows the identification of source types and their respective excitation of the hull and emission characteristics of the hydrodynamic sources into the fluid domain, as well as the effect of the CFD simulation domain geometry extent.

Biobased Polylactic (PLA) foams are cellular materials with distinctive characteristics namely its good biocompatibility and biodegradability, enabled it to be incorporated in various applications such as food packaging, drug delivery, and tissue engineering scaffolds.[1] However, the low melt strength and low crystallization rate of PLA negatively affect cell growth causing non-uniform cellular structure and cell collapse[2]. Natural organic fibers such as lignin present an effective method that can significantly improve the crystallization kinetics of PLA and provide nucleation sites[3][2]. Conventionally, the foaming of polymeric blends is obtained by the addition of a chemical or physical blowing agents; the chemical agent does not give a good control of the porosity and also implies the presence of residues while the physical agents such as chlorofluorocarbons are known for their contribution to the depletion of the ozone layer. The recent focus has been steered into the use of carbon dioxide (CO2) as it offers lower operating condition, relative ease of handle and additionally acts as plasticizer due to its solubility in molten polymers [4] However complete understanding of the CO2 foaming process, particularly nucleation, is lacking [5] This research aims to gain complete understanding of the lignin PLA foaming process using CO2. To accomplish this goal, the experimental work is divided into two main parts: the experimental work in the first part focuses on investigating the foaming behavior of various extruded lignin PLA blends with lignin percentages of 10-30 wt %, The foaming is done via Batch CO2 and compared to other blowing agents foaming such as sodium bicarbonate and microspheres. The lignin PLA foams are then characterized by their cellular structure, volume expansion ratio and density. The second part investigates lignin PLA extrusion process coupled with continuous CO2 foaming; where CO2 acts as a solvent for the molten polymeric blend in the extru

Technological transitions of aircraft propulsion concepts are a key strategy for reducing the environmental impacts of air travel. Using battery-electric and fuel cell-based powertrains can avoid climate-damaging CO2 and non-CO2 emissions from kerosene combustion in conventional jet engines. However, the long service life of aircraft requires extensive maintenance, repair, and overhaul (MRO) processes of the powertrain. The main components of novel powertrain concepts (e.g., batteries, fuel cells, and electric motors) might require more frequent replacements than conventional powertrain components, leading to negative impacts on sustainability. Therefore, this article analyzes the environmental and economic impacts of novel powertrain concepts associated with their MRO. For this purpose, the aging behavior of the main components is analyzed, and replacement times are determined. Using life cycle assessment and life cycle costing, the MRO-related impacts of novel powertrain concepts are investigated and compared to those of conventional jet engines. The analysis shows that batteries, fuel cells, and electric motors must be replaced more often than conventional jet engines. In addition, the replacement frequency of batteries and fuel cells results in higher environmental impacts than conventional jet engines., Deutsche Forschungsgemeinschaft (DFG)

One of the major applications (40% in Europe) of plastic is packaging, which is often printed to display required information and to deliver an attractive aesthetic for marketing purposes. However, printing ink can cause contamination in the mechanical recycling process. To mitigate this issue, the use of surfactants in an alkaline washing process, known as de-inking, has been employed to remove printing ink and improve the quality of recyclates. Despite the existence of this technology, there are currently no data linking the de-inking efficiency with typical printing ink compositions. Additionally, it is necessary to investigate the de-inking process under the process parameters of existing recycling plants, including temperature, NaOH concentration, and retention time. This study aims to evaluate the performance of commonly used printing inks with different compositions under various washing scenarios for plastic recycling in conjunction with different de-inking detergents containing surfactants or mixtures of surfactants. The results indicate that the pigments applied to the ink have no significant effect on the de-inking process, except for carbon black (PBk 7). Nitrocellulose (NC) binder systems exhibit high de-inkability (over 95%) under the condition of 55 °C and 1 wt.% NaOH. However, crosslinked binder systems can impede the de-inking effect, whether used as a binder system or as an overprint varnish (OPV). The de-inking process requires heating to 55 °C with 1 wt.% NaOH to achieve a substantial effect. Based on the findings in this work, breaking the Van der Waals forces, hydrogen bonds, and covalent bonds between the printing ink and plastic film is an essential step to achieve the de-inking effect. Further research is needed to understand the interaction between surfactants and printing inks, enabling the development of de-inkable printing inks and high-performance surfactants that allow for de-inking with less energy consumption. The surfactant and NaOH

Die Arbeit handelt von der Entwicklung einer numerischen Methode zur Simulation von Anlegemanövern von Serviceschiffen an Offshore-Plattformen. Der Ansatz basiert auf einer Randelemente-Methode und berechnet das Landemanöver im Zeitbereich unter Berücksichtigung der nicht-linearen freien Wasseroberfläche. Ein Kontakt-Model wird zur Beschreibung der Reibkräfte zwischen Fender und Anlegestruktur und zur Bestimmung, ob der Fender während des Manövers ins Rutschen gerät oder nicht, verwendet. Des Weiteren werden Modellversuche in Wellen durchgeführt. Die experimentellen Daten werden zur Validierung verwendet. Es wird gezeigt, dass die Methode das Landemanöver simulieren und das Abrutschen des Fenders prognostizieren kann., The thesis is about the development of a numerical method for the simulation of boat-landing maneuver at offshore platforms. The approach is based on a boundary panel method, and it computes the boat-landing maneuver in the time domain considering the non-linear free water surface. A fender contact model is applied to describe the friction forces between fender and boat-landing struts and to detect whether the fender slips or not during the landing maneuver. Furthermore, model tests are conducted in waves. The experimental data is used to validate the developed method. It is demonstrated that the approach is able to simulate the boat-landing maneuver and that it is able to forecast the occurrence of slip during the maneuver., Behörde für Wissenschaft und Forschung

The constitutive relation of Skorohod and Olevsky for viscous sintering is utilized to model the shrinkage and relative density evolution during the sintering process of ceramics. A new implicit integration scheme is presented and implemented. The computational cost is drastically reduced by combining this integration scheme with a solid-like shell element formulation, which also enables a faster and more accurate description of shape distortions, especially for thin geometries. The characterization and identification of the material viscosity is also improved via the Aquilanti–Mundim deformed Arrhenius description. The model robustness is examined with a spectrum of benchmark tests: ZnO sintering experiments from previous studies, as well as new lanthanum tungstate sintering tests. The model predictions for both dimensional shrinkage and relative density evolution are very accurate using the newly proposed material viscosity functions. The model improvements offer the possibility to simulate long-time sintering processes with higher accuracy and significantly reduced computational efforts.

In dieser Arbeit wird die Entwicklung der folgenden mikrostrukturellen Merkmale untersucht: Restsilber, charakteristische Längenskala und topologische Konnektivität in nanoporösem Gold (NPG). Die kinetische Monte-Carlo-Methode wurde verwendet, um die Entlegierungs und Vergröberungsprozesse zu simulieren. Der Schrumpfungsprozess der NPG-Strukturen wurde mit Molekulardynamik simuliert. Es wurde festgestellt, dass die Entlegierung in zwei Phasen abläuft. Beim primären Entlegieren werden Silbercluster in die Ligamente eingebettet; beim sekundären Entlegieren wird die Anzahl der Silbercluster reduziert. Die Größe der Silbercluster bleibt während des gesamten Entlegieren konstant und skaliert mit der ursprünglichen Ligamentgröße, die beim primären Entlegieren festgelegt wurde. Die Feststellung des Vergröberungsgesetzes liefert Erklärung für verstreute experimentelle Ergebnisse. Diese Arbeit zeigt, dass der Feststoffanteil eine wichtige Rolle bei der Entwicklung der Konnektivität des nanoporösen Netzwerks während der Entlegierungs, Vergröberungs und Schrumpfungsprozesse spielt., This thesis explores the evolution of these microstructural features: residual silver, characteristic length scale, and topological connectivity in nanoporous gold (NPG). Kinetic Monte Carlo was used to simulate the dealloying and coarsening processes. Molecular Dynamics was used to simulate the shrinkage process of NPG structures. It is found that the dealloying occurs in two stages. In the primary dealloying, silver clusters are embedded in the ligaments; in the secondary dealloying, the number of silver clusters is reduced. The silver cluster size retains constant during the whole dealloying and scales with the initial ligament size established in the primary dealloying. The finding of coarsening law provides a conclusive confirmation for scattered experimental results. This thesis points out that the solid fraction plays a significant role in the evolution of the nanoporous network’s connectivity during the dealloying, coarsening and shrinkage processes., Deutsche Forschungsgemeinschaft

The increasing number of electric vehicles worldwide leads to various challenges, especially in terms of battery supply chains. New battery production sites, raw material refiners, and extraction sites will be needed to fulfill the future battery demand. Additionally, the planned European Battery Directive requires battery manufacturers to meet defined CO2-limits and social standards to enter the European market. However, depending on the design of battery supply chains, environmental and socio-economic impacts can vary considerably. Especially the selection of suppliers as well as production locations and processes can have a major influence. Therefore, the aim of this study is to investigate battery supply chain options to highlight the differences and trade-offs related to the three sustainability dimensions. For this purpose, a life cycle sustainability assessment is conducted, considering a baseline scenario depicting the global average production shares, and three additional scenarios to investigate the influence of locations on three processes along the supply chain. The results provide insights into the design of sustainable battery supply chains. It is shown how different locations and battery types affect the indicator scores of the investigated supply chains. Furthermore, the results indicate distinct trade-offs between the three sustainability dimensions and underline the necessity for the subsequent use of multi-criteria decision-making models to derive recommendations for designing sustainable battery supply chains., Bundesministerium für Bildung und Forschung (BMBF)