Publications

Members of TU Berlin can publish different kinds of (text) publications on DepositOnce:

  • publications with academic content such as monographs and collected editions, journal articles and book chapters, conference proceedings and conference papers, research reports,
  • publications that must be made public in connection with examination regulations (doctoral theses and post-doctoral theses),
  • theses of TU Berlin students if the thesis has received the grade "very good" and the publication is endorsed by the supervisor or referee.

The following publication types can be selected: Doctoral thesis, Habilitation, Master thesis, Bachelor thesis, Book, Conference Proceedings, Periodical Part, Preprint, Report, Research Paper, Article, Book Part, Conference Object

For further information on requirements and workflows see Checklists and Hints for Publishing.

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Recent Submissions

Now showing 1 - 20 of 16818
  • Arsenic-poor fluids promote strong As partitioning into pyrite

    Pyrite is a ubiquitous sulfide mineral found in diverse geological settings and holds great significance in the formation of Au deposits as well as the safe utilization of groundwater due to its remarkable ability to incorporate substantial amounts of As. However, despite its importance, there remains a dearth of fundamental data on the partitioning of As between pyrite and fluid, which is key for accurately modeling the As distribution in these environments. Here, we present new insights into the partitioning behavior of As between pyrite and fluid at conditions that mimic natural fluid systems. Pyrite was synthesized by replacement of natural siderite in hydrothermal experiments at 200 °C and pH 5 applying a wide range of fluid As concentrations, spanning from 0.001 to 100 µg/g. The As distribution and concentration in synthetic pyrite was analyzed by quantitative LA-ICP-MS mapping providing a high spatial resolution and sensitivity at 2–3 µm image pixel size at a detection limit of ∼1 µg/g at the single pixel scale. Pyrite-fluid partitioning coefficients (DAs(py/fluid)) between synthetic pyrite and experimental fluid agree with previously published data for high fluid As concentrations of 1 µg/g to 100 µg/g (DAs < 2000). However, at low As concentrations in the experimental fluid (<1 µg/g), a steep increase in the DAs(py/fluid) values of up to ∼30,000 was detected, demonstrating even stronger As partitioning into pyrite. This is confirmed by the analyses of natural pyrite that precipitated from As-poor fluids (0.3–0.4 ng/g) within a deep anoxic aquifer in SE Sweden. The discovery holds significant implications for the mobility and scavenging of As, which in turn is important for understanding the formation and fingerprinting of mineral deposits as well as for the secure utilization of groundwater resources.
  • Beyond built density: From coarse to fine-grained analyses of emotional experiences in urban environments

    The migration of individuals to urban centers in the last century has coincided with a rise in stress-related mental health issues among city dwellers compared to their rural counterparts. Neurourbanism, a burgeoning field, seeks to comprehend the determinants of individual well-being within the urban context. This study investigated the impact of urban density on subjective emotional experiences with a focus on how urban density factors are operationalized in this research field. Using a remote desktop protocol coupled with eye tracking technology, we presented participants with realistic urban stimuli from Berlin, Germany, to assess gaze patterns and subjective responses. Following a two-step analytical approach, we first used a two-factorial design based on low/high built density and absent/present greenery, reflecting the common approach to operationalizing urban density. Subsequently, semantic segmentation of the stimuli was performed, providing a more fine-grained, continuous quantification of density factors allowing for a comparison of this approach with the first categorical analysis. Lastly, individual gaze patterns were exploratively analyzed to predict the impact of directed attention to different classes of urban density on subjective experiences. Dichotomous classification replicated previous findings indicating that high built density was associated with more negative subjective ratings compared to low density, and images lacking greenery received more negative ratings than those with green spaces. Using a continuous quantification of urban density factors and adding additional object classes (cars, people, sky) led to different results compared to the dichotomous approach. Gaze patterns only partially echoed subjective ratings, suggesting urban density factors influence ratings via a general urban scene impression without the need for directed attention towards them. These findings underscore the multifaceted influence of density factors on emotional appraisal in urban spaces, emphasizing the importance of chosen methods. The study demonstrates that fine-grained analyses of urban density factors enhance our understanding of how the urban environment affects the well-being of city dwellers.
  • The optimal experiment? Influence of solution strategies on model-based optimal experimental design

    Model-based optimal experimental design (OED) is a well known tool for efficient model development. However, it is not used very often. A few reasons for that are: a lack of understanding on how to work with complex OED methods and a small amount of ready-to-use tools available to directly apply OED methods. In the presented contribution OED and sampling strategies are used to categorize OED formulations as nonlinear programs. Different strategies and their combination are analyzed based on performance and robustness. Depending on the availability of measurements, control flexibility of the experimental setup, and model accuracy some strategies are more efficient than others. Based on the proposed guidelines, engineers will have a better understanding about which NLP formulation should be used for their specific task. The methods described are available to the community as a part of open-source code developed in Python.
  • Impact of the reductive deiodination on the sorption of iodinated X-ray contrast media to filter sand and activated carbon

    Iodinated X-ray contrast media (ICM) and their aerobic transformation products (TPs) are widespread in the aquatic environment due to their persistent and mobile character. In a previous lab study, we have shown that the reductive (partial) deiodination of selected triiodobenzene derivatives increases the sorption to aquifer sand and loam soil, since iodine affects the compounds by steric hindrance, repulsive forces, resonance and inductive effects. These results suggest that the (partial) deiodination generally occurring to ICM and aerobic ICM TPs during anoxic/anaerobic bank filtration has a potential to increase their removal by sorption to natural sorbents. To basically assess the sorption potential to technically applied materials for drinking water treatment subsequent to bank filtration, we investigated the sorption of iopromide, diatrizoate and 5-amino-2,4,6-triiodoisophtalic acid and their di, mono and deiodinated structures to used filter sand from a waterworks and different fresh powdered activated carbons in batch tests using Berlin drinking water. The filter material, coated by iron and manganese oxides as well as organic material (including biofilm), preferentially removed monoiodinated derivatives, but diffusion through the organic layer heavily slowed the sorption. Therefore, the removal potential by sorption in rapid sand filters of waterworks for (partially) deiodinated benzene derivatives is suggested to be low. The deiodination of iopromide and diatrizoate significantly increased the sorption affinity to activated carbon and the competitiveness with regard to drinking water DOC. Despite the large atom radius of iodine, no clear correlation was found between the pore characteristics of the activated carbons and the molecular size of the compounds. This study emphasises the importance of anoxic/anaerobic conditions for the removal of persistent and mobile ICM and ICM TPs during drinking water treatment.
  • Exploring transverse particle motion in rotary drums: DEM analysis of the influence of cross-shaped internals on material transport

    This study investigates the impact of lifters and cross-shaped internals on the transversal movement of wooden spheres within rotary drums. Utilizing Discrete Element Method (DEM) simulations, the research evaluates the influence of these internal configurations on evolving bulk porosity, particle trajectories and residence time of particles in the central area of the drum. The study analyzes three distinct internal geometries and the influences of parameters such as drum rotational speed, drum fill level, and particle water content. Analysis of the simulation results shows that the mean bulk porosity increases by 4% for a single internal cross and by 7% for four internal crosses compared to a configuration without internals. Additionally, it is observed that the residence time for particles in the center of the drum increases by an average of 2.5 times for a single internal cross and 5.5 times for four internal crosses compared to a configuration without internals.
  • Some inconvenient truths about decarbonization, the hydrogen economy, and power-to-X technologies

    The decarbonization of the energy sector has been a subject of research and of political discussions for several decades, gaining significant attention in the last years. It is commonly acknowledged that the most obvious way to achieve decarbonization is the use of renewable energy sources. Within the context of the energy sector decarbonization, many mainly industrialized countries recently started developing national plans to establish a hydrogen-based economy in the very near future. The plans for green hydrogen initially try to (a) target sectors that are difficult to decarbonize and (b) address issues related to the storage and transportation of CO2-free energy. To achieve almost complete decarbonization, electric power must be generated exclusively from renewable sources. In so-called Power-to-X (PtX) technologies, green hydrogen is generated from electricity and subsequently converted to another energy carrier which can be further stored, transported and used. In PtX, X stands, for example, for liquid hydrogen, methanol or ammonia. The challenges associated with decarbonization include those associated with (a) the expansion of renewable energies (e.g., high capital demand, political and social issues), (b) the production, transportation, and storage of hydrogen and the energy carriers denoted by X in PtX (e.g., high cost and low overall efficiency), and (c) the expected significant increase in the demand for electrical energy. The paper discusses whether and under which conditions the current national and international hydrogen plans of many industrialized countries could lead to a maximization of decarbonization in the world. It concludes that, in general, as long as the conditions for generating large excess amounts of green electricity are not met, the quick establishment of a hydrogen economy could not only be very expensive, but also counterproductive to the worldwide decarbonization efforts.
  • Adhesive sliding with a nominal point contact: Postpredictive analysis

    Quasi-static sliding contact of an axisymmetric convex rigid solid with an adhesive incompressible polymer layer bonded to a rigid base is considered. As generalizations of the state-of-the-art theories of interplay between adhesion and friction, the JKR (Johnson–Kendall–Roberts)-type so-called peeling and sliding models are developed and applied for analyzing a set of experimental data for spherical indenters of various radii, which is available in the literature. A special focus is placed on the acquisition of the model parameters from experimental data in the case of a nominal point contact. The postpredictive analysis of the obtained scaled results indicates the existence of a three-stage adhesive attachment-stick/peeling/sliding periodic instability.
  • Evaluating the efficiency and performance of data persistent systems in managing building and environmental Data: A comparative study

    Selecting an appropriate data persistent system for a specific use case necessitates a thorough examination of the application domain and the characteristics of the data expected to be stored. While comparative studies of data persistent systems exist in various domains, there is a notable absence of such studies concerning building and environmental data management. This research aims to bridge this gap by conducting a comparative evaluation based on building and environmental datasets and use cases. The study primarily focuses on two types of database systems, namely relational database systems and graph-based database systems. Two building and two city models are employed in the evaluation. The building data sets are extracted from IFC models, and environmental data are extracted from CityGML and OpenStreetMap. The assessment involves qualitatively analysing the database design process of the systems and quantitatively evaluating the efficiency of retrieving data from those systems. The comparative evaluation identifies at least two crucial aspects to consider when selecting a suitable data-persistent system for managing building and environmental data. The first aspect pertains to the stability of the data to be stored, along with the complexity of interrelationships within the building and environmental dataset. The second aspect involves the manner in which data is retrieved to accomplish different tasks within the particular business case. The findings demonstrate that use cases that typically manage interrelated data and necessitate the traversal of complex relationships between building and environmental features are better managed by graph-based database systems, particularly when dealing with large datasets. Conversely, relational databases exhibit superior performance for use cases requiring minimal or no relationship traversal, regardless of dataset size. The contributions of this study can serve as valuable input when designing information management tools and systems for building and environmental data management.
  • Evaluation of a concentrated solar power plant under meteorological and climatological forcing

    The performance of renewable energy-conversion systems depends strongly on the background climate and ambient meteorological conditions. However, common approaches to simulating such systems use aggregated climatic data as forcing. Given strong variability in the climate, along with possible future long-term changes, it is important to understand the trade-offs between high-resolution forcing data and representative data. Here we simulate a concentrated solar power plant driven by hourly-resolved reanalysis data using both air and water-based cooling systems. These simulations allow us to analyze plant performance under realistic meteorological variability at two locations. In addition, we simulate the plant under average climatic conditions, where all sub-seasonal and interannual variability has been removed. These simulations are cheaper to run, but do not represent extreme values in the forcing. Our analysis shows that variability in the direct normal irradiance (DNI) is a critical factor for simulating the plant realistically. We show that where (and when) DNI variability is low, average forcing provides a realistic picture of power output. Average forcing can also provide a good estimate of how the plant will perform on average. However, in cases where understanding how robustly the plant performs, it is critical to include realistic variability in the input data.
  • Interaction and competition for intestinal absorption by zinc, iron, copper, and manganese at the intestinal mucus layer

    Trace elements such as zinc, manganese, copper, or iron are essential for a wide range of physiological functions. It is therefore crucial to ensure an adequate supply of these elements to the body. Many previous investigations have dealt with the role of transport proteins, in particular their selectivity for, and competition between, different ions. Another so far less well investigated major factor influencing the absorption of trace elements seems to be the intestinal mucus layer. This gel-like substance covers the entire gastrointestinal tract and its physiochemical properties can be mainly assigned to the glycoproteins it contains, so-called mucins. Interaction with mucins has already been demonstrated for some metals. However, knowledge about the impact on the respective bioavailability and competition between those metals is still sketchy. This review therefore aims to summarize the findings and knowledge gaps about potential effects regarding the interaction between gastrointestinal mucins and the trace elements iron, zinc, manganese, and copper. Mucins play an indispensable role in the absorption of these trace elements in the neutral to slightly alkaline environment of the intestine, by keeping them in a soluble form that can be absorbed by enterocytes. Furthermore, the studies so far indicate that the competition between these trace elements for uptake already starts at the intestinal mucus layer, yet further research is required to completely understand this interaction.
  • Spectral-temporal traits in Sentinel-1 C-band SAR and Sentinel-2 multispectral remote sensing time series for 61 tree species in Central Europe

    Tree species maps derived from satellite imagery increasingly support forest administrations and nature conservation authorities with large-scale and up-to-date information. However, many species are often excluded or aggregated in classification tasks due to a limited knowledge of the most suitable predictors. Our study aims to gain a better understanding of optical and polarimetric traits for tree species mapping by examining Sentinel-1 and Sentinel-2 time series from 61 tree species in temperate Europe. For a selection of 32 optical, polarimetric and structural variables, the principal component analysis revealed that Sentinel-2 variables mainly explain the variance in the data by contributing to the “seasonality” and “foliage color” components. Sentinel-1 contribute most to the “texture” component. The Normalized Difference Vegetation Index (NDVI), Tasseled Cap Greenness (TCG) and Radar Vegetation Index (RVI) were chosen as key variables for further analysis. Seasonality was found to be the most dominant aspect in all vegetation indices. Furthermore, the TCG was found to be useful to distinguish between early and late budding species. The RVI showed a large potential to discriminate conifers, which is attributed to the crown volume effect of C-band SAR. Using exploratory data analysis, we further examined the influence of management, biogeographical and meteorological factors on the time series from Fagus sylvatica, Pinus sylvestris, and Picea abies. The NDVI and TCG are relatively robust to different conditions. For the two conifer species however, we found strong spatial variations of the RVI which are presumably caused by different crown conditions across the study area. Using Sentinel-1 data could therefore lead to uncertainties in tree species mapping across large biogeographical gradients. This study contributes to the improvement of tree species mapping based on optical and dual-polarimetric data and thus benefits forest authorities and other stakeholders in their monitoring tasks and decision-making.
  • De Casteljau's algorithm in geometric data analysis: Theory and application

    For decades, de Casteljau's algorithm has been used as a fundamental building block in curve and surface design and has found a wide range of applications in fields such as scientific computing and discrete geometry, to name but a few. With increasing interest in nonlinear data science, its constructive approach has been shown to provide a principled way to generalize parametric smooth curves to manifolds. These curves have found remarkable new applications in the analysis of parameter-dependent, geometric data. This article provides a survey of the recent theoretical developments in this exciting area as well as its applications in fields such as geometric morphometrics and longitudinal data analysis in medicine, archaeology, and meteorology.
  • ConfigILM: A general purpose configurable library for combining image and language models for visual question answering

    ConfigILM is an open-source Python library for rapid iterative development of image-language models for visual question answering in PyTorch. It provides a convenient implementation for seamlessly combining image and language models from two popular PyTorch libraries that are timm and huggingface. These libraries allow a variety of configurations of models without additional implementation effort. The monolithic interface provided by ConfigILM simplifies the exchange of components of a considered model and offers possibilities for developing new image-language models based on recombining the selected encoders. Additionally, the library provides pre-built and throughput-optimized PyTorch dataloaders. We also provide a guideline document that contains installation instructions, tutorial examples, and a complete discussion of the monolithic interface to the library. ConfigILM is released under the MIT License, encouraging its use in academic and commercial environments. The source code and documentation of ConfigILM are available at https://github.com/lhackel-tub/ConfigILM
  • Elliptic p-Laplacian systems with nonlinear boundary condition

    In this paper we study quasilinear elliptic systems given by −Δp1u1 = −|u1|p1−2u1 in Ω, −Δp2u2 = −|u2|p2−2u2 in Ω, |∇u1|p1−2∇u1 · ν = g1(x, u1, u2) on∂Ω, |∇u2|p2−2∇u2 · ν = g2(x, u1, u2) on∂Ω, where ν(x)is the outer unit normal of Ωat x ∈∂Ω, Δpidenotes the pi-Laplacian and gi:∂Ω ×R ×R →Rare Carathéodory functions that satisfy general growth and structure conditions for i =1, 2. In the first part we prove the existence of a positive minimal and a negative maximal solution based on an appropriate construction of sub-and supersolution along with a certain behavior of ginear zero related to the first eigenvalue of the pi-Laplacian with Steklov boundary condition. The second part is related to the existence of a third nontrivial solution by imposing a variational structure, that is, (g1, g2) =∇gwith a smooth function (s1, s2) →g(x, s1, s2). By using the variational characterization of the second eigenvalue of the Steklov eigenvalue problem for the pi-Laplacian together with the properties of the related truncated energy functionals, which are in general nonsmooth, we show the existence of a nontrivial solution whose components lie between the components of the positive minimal and the negative maximal solution.
  • Autonomous self-healing behavior of geopolymer pastes under varied curing environments

    This study examined the effectiveness of incorporating self-healing capsules based on sodium silicate in geopolymers containing fly ash and metakaolin. To evaluate the self-healing capabilities, geopolymer samples with the self-healing capsules were preloaded and subjected to different healing conditions: 100% relative humidity at room temperature, 100% relative humidity at 60°C, and water curing. The crack sealing capability, compressive strength recovery, and changes in the sorptivity coefficient of the geopolymer paste with varying amounts of self-healing capsules were investigated. The self-healing process performed under 100%RH-60°C resulted in the highest crack sealing efficiency (91.6±18.53%), mechanical recovery, and improved water tightness. XRD, FT-IR, and SEM-EDX techniques confirmed that primary self-healing products were amorphous aluminosilicates.
  • Seasonal performance assessment and experimental investigation of R32 drop-in and BPHX size in an R410A chiller when using two compressor modulation strategies

    The decrease in fossil fuel reserves and high energy consumption by HVAC&R equipment require the use of compressors with better efficiencies and capacity modulation strategies. Usually, seasonal performance studies focus on compressor capacity modulation methods, however the current study explores the idea of improving the seasonal performance of two compressor modulation techniques: a two-stage and a variable speed compressor with different capacity modulation ranges by using larger condensers in an R410A water ethylene glycol chiller system. The analysis shows that oversizing the heat exchangers has larger benefits with the compressor modulation strategy with lower range. Additionally, the seasonal performance estimated according to AHRI 551/591 (2020) of a two-stage compressor with oversized condenser is higher than a basic single speed compressor with a better motor indicating that oversizing brazed plate heat exchanger (BPHX) might yield higher performance than improving the compressor motor efficiency. Due to the high global warming potential (GWP) of R410A, there is a focus on replacing it with low GWP refrigerants such as R32 to reduce CO2 emissions. This study would also compare the performance when using R32 as a drop-in refrigerant in the two different R410A compressor capacity modulation strategies with comparable cooling capacity. When the refrigerant was changed from R410A to R32, the integrated part load value (IPLV.SI), an efficiency metric for variable speed compressor remains relatively constant at 5.5 while it increases from 3.9 to 4.4 for the two-stage compressor. It is hypothesized that low refrigerant mass flow rate (m˙ ref) provided by the variable speed compressor when matching the load at the lower part load conditions leads to refrigerant maldistribution in BPHX and reduced IPLV.SI. .
  • Determination of copper status by five biomarkers in serum of healthy women

    Background The essential trace element copper is relevant for many important physiological processes. Changes in copper homeostasis can result from disease and affect human health. A reliable assessment of copper status by suitable biomarkers may enable fast detection of subtle changes in copper metabolism. To this end, additional biomarkers besides serum copper and ceruloplasmin (CP) concentrations are required. Objectives The aim of this study was to investigate the emerging copper biomarkers CP oxidase (CPO) activity, exchangeable copper (CuEXC) and labile copper in serum of healthy women and compare them with the conventional biomarkers total serum copper and CP. Method and main findings This observational study determined CPO activity, the non CP-bound copper species CuEXC and labile copper, total serum copper and CP in sera of 110 healthy women. Samples were collected at four time points over a period of 24 weeks. The concentrations of total serum copper and CP were within the reference ranges. The comparison of all five biomarkers provided insight into their relationship, the intra- and inter-individual variability as well as the age dependence. The correlation and Principal Component Analyses (PCA) indicated that CP, CPO activity and total copper correlated well, followed by CuEXC, while the labile copper pool was unrelated to the other parameters. Conclusions This study suggests that the non-CP-bound copper species represent copper pools that are differently regulated from total copper or CP-bound copper, making them interesting complementary biomarkers to enable a more complete assessment of body copper status with potential relevance for clinical application.
  • Automatic initial value generation procedure for nonlinear process models by interval arithmetic based cutting and splitting

    To solve large nonlinear equation systems, we present a hybrid method based on interval arithmetic and real-valued root-finding. The proposed approach includes two new interval arithmetic based methods, the so-called cutting and a special kind of bisection of consistent variable spaces. Applied to three examples from chemical engineering, it is shown that the approach is now able to find all system solutions within a variable space as well as only one process-relevant solution in much less time thanks to the built-in root-finding step. For the latter, a conventional Newton method as well as IPOPT have been examined. The hybrid approach no longer needs a well-estimated initial point to converge to a solution, only rough initial variable bounds are required.
  • Modeling Elongational Rheology of Model Poly((±)-lactide) Graft Copolymer Bottlebrushes

    The shear and elongational rheology of graft polymers with poly(norbornene) backbone and one poly((±)-lactide) side chain of length Nsc = 72 per two backbone repeat units (grafting density z = 0.5) was investigated recently by Zografos et al. [Macromolecules 56, 2406–2417 (2023)]. Above the star-to-bottlebrush transition at backbone degrees of polymerization of Nbb>70, increasing strain hardening was observed with increasing Nbb, which was attributed to side-chain interdigitation resulting in enhanced friction in bottlebrush polymers. Here we show that the elongational rheology of the copolymers with entangled side chains and an unentangled backbone can be explained by the Hierarchical Multi-mode Molecular Stress Function (HMMSF) model, which takes into account hierarchical relaxation and dynamic dilution of the backbone by the side chains, leading to constrained Rouse relaxation. In nonlinear viscoelastic flows with larger Weissenberg numbers, the effect of dynamic dilution is increasingly reduced leading to stretch of the backbone chain caused by side chain constraints and resulting in strain hardening. If the backbone is sufficiently long, hyperstretching is observed at larger strain rates, i.e. the stress growth is greater than expected from affine stretch.
  • Wheel flat detection by using the angular domain synchronous averaging method and axle box acceleration: Simulation and experiment

    Wheel flats (WFs) can generate periodic impact forces and aggravate the wheel-rail interaction. Therefore, the early detection of WFs is significant for railway operators to lower the maintenance cost. In this work, the angular domain synchronous averaging (ADSA) method is employed to detect WFs on railway vehicles since it can handle the non-stationary vibration process of rotating machines by processing the vibration data in the angular domain. Furthermore, the short-time irregular impulses, such as those caused by crossings and rail joints, can be attenuated by using synchronous averaging technology. The periodic impact caused by WFs can be easily observed in the polar coordinate using the ADSA method, which is verified by one multibody system (MBS) simulation and one field experiment. Besides, the sensitivity of this method to various flat dimensions and multiple flats is also studied in the MBS simulation.