opus htw (Hochschule für Technik und Wirtschaft Berlin)
Not a member yet
1647 research outputs found
Sort by
Advancement of Electrospun Carbon Nanofiber Mats in Sensor Technology for Air Pollutant Detection †
No full textThe use of electrospun carbon nanofibers (ECNs) has been the focus of considerable interest due to their potential implementation in sensing. These ECNs have unique structural and morphological features such as high surface area-to-volume ratio, cross-linked pore structure, and good conductivity, making them well suited for sensing applications. Electrospinning technology, in which polymer solutions or melts are electrostatically deposited, enables the production of high-performance nanofibers with tailored properties, including fiber diameter, porosity, and composition. This controllability enables the use of ECNs to optimize sensing applications, resulting in improved sensor performance and sensitivity. While carbon nanofiber mats have potential for sensor applications, several challenges remain to improve selectivity, sensitivity, stability and scalability. Sensor technologies play a critical role in the global sharing of environmental data, facilitating collaboration to address transboundary pollution issues and fostering international cooperation to find solutions to common environmental challenges. The use of carbon nanofibers for the detection of air pollutants offers a variety of possibilities for industrial applications in different sectors, ranging from healthcare to materials science. For example, optical, piezoelectric and resistive ECNs sensors effectively monitor particulate matter, while chemoresistive and catalytic ECNs sensors are particularly good at detecting gaseous pollutants. For heavy metals, electrochemical ECNF sensors offer accurate and reliable detection. This brief review provides in-sights into the latest developments and findings in the fabrication, properties and applications of ECNs in the field of sensing. The efficient utilization of these resources holds significant potential for meeting the evolving needs of sensing technologies in various fields, with a particular focus on air pollutant detection
Rust in der Entwicklung von Microservices: Reimplementierung einer Spring Boot Applikation
No full textAs part of this Bachelor’s thesis, an existing Java microservice was reimplemented in the Rust programming language.
The goal was to assess the feasibility and potential advantages of such a migration with regard to architecture and performance. For this purpose, both the original system and the newly developed Rust service were tested under various scenarios to identify differences in latency, throughput, and resource usage.
This thesis provides insights into Rust’s strict type system and ownership model, comparing them with Java’s established mechanisms. The aim is to provide a reasonable technical foundation for future web development projects, in which Rust may serve as a viable alternative to established technologies.Im Rahmen dieser Arbeit wurde ein bestehender Java-Microservice in der Programmier sprache Rust neu implementiert.
Ziel war es, die Machbarkeit und potenziellen Vorteile einer solchen Migration hinsichtlich Architektur und Performance zu untersuchen. Zu diesem Zweck wurde sowohl das bestehende Java-System als auch der neu entwickelte Rust-Dienst unter verschiedenen Szenarien getestet, um Unterschiede in Bezug auf Latenz, Durchsatz und Ressourcennutzung zu identifizieren.
Die Arbeit gibt einen Einblick in die Eigenheiten von Rusts strikten Typsystem und Ownership-Modell und stellt diese den etablierten Mechanismen von Java gegenüber. Damit sollen technische Entscheidungsgrundlagen für künftige Projekte im Bereich der Webentwicklung geschaffen werden, bei denen Rust als Alternative zu etablierten Technologien in Betracht gezogen wird
Museum of the Invisible - How museums can meaningfully engage with and support people experiencing homelessness
No full textThis thesis investigates the potential for museums to engage meaningfully with people experiencing homelessness through a spectrum of practical and strategic measures. Drawing on case studies, theoretical frameworks, and participatory methodologies, it examines how institutions can move beyond representational approaches to foster co-creation, empowerment, and long-term social impact. The research identifies actions ranging from simple, immediately implementable measures to complex, resource intensive commitments, applicable to museums of any size or type. Particular attention is given to trans-disciplinary collaboration, the recognition of lived experience as expertise, and the integration of social justice into institutional structures. The paper argues that museums have both the capacity and the responsibility to act as civic actors in addressing homelessness
Labels4Rails: A Railway Image Annotation Tool and Associated Reference Dataset
No full textThe development of autonomous train systems relies heavily on machine learning (ML) models, which in turn depend on large, high-quality annotated datasets for training and evaluation. The railway domain lacks adequate public datasets and efficient annotation tools. To address this gap, we present Labels4Rails, a tool designed specifically for the annotation of railway scenes. It captures track topology, switch states including switch directions, and informational tags regarding the images’ content and leverages consistent camera perspectives and the fixed track geometries inherent to railways for annotation efficiency. We used Labels4Rails to create the L4R_NLB reference dataset from Norwegian railway footage. The dataset contains 10,253 annotated images across four seasons, including 1415 switch annotations. Both the tool and dataset are publicly available
Optical Simulations of Nanotextured All‐Perovskite Tandem Solar Cells
No full textThis numerical study investigates, how textures at various locations of all‐perovskite tandem solar cells affect their optical performance. For this, hexagonal sinusoidal textures with 750 nm period and aspect ratios (height‐to‐period) of 27% (moderate) and 54% (pronounced) are considered. The optical simulations are performed with the finite element method and an algorithm to correct for the thick glass superstrate. The complex refractive index data of the wide‐bandgap (WBG) and narrow‐bandgap (NBG) perovskites with spectroscopic ellipsometry is determined. Texturing between the glass superstrate and the WBG perovskite top cell has an antireflective effect across the whole wavelength region. In contrast, texturing between the WBG perovskite top cell and the NBG perovskite bottom cell has no additional effect for a moderate texture but leads to light trapping in the NBG perovskite for a pronounced texture. Moderate texturing between the NBG perovskite absorber and the metal back contact leads to light trapping in the NBG perovskite but also excites surface plasmons in the copper back contact. Dielectric interlayers between the NBG perovskite and the metal back contact can reduce the plasmonic absorption losses. Texturing potentially allows to increase the current‐matched short‐circuit current density beyond 17 mA cm−2
M&As and Corporate Financial Performance: An Empirical Study of DAX 40 Firms
No full textThis study examines the impact of mergers and acquisitions (M&As) on the financial performance of firms listed in Germany’s DAX 40 index. Although M&As are a widely used strategic tool intended to create value through synergies and market expansion, existing research provides conflicting evidence about their effectiveness. Using an empirical approach, we analyze the financial data of acquiring companies before and post-M&A transactions to evaluate changes in profitability, liquidity and solvency. Our findings suggest that financial performance does not universally improve following acquisitions. Instead, results vary significantly based on deal characteristics and internal management factors. These results suggest that, while M&A can be a pathway to growth, success depends heavily on the quality of execution and organizational integration. This paper contributes to the ongoing debate about the effectiveness of M&As and provides insights for corporate decision-makers, investors, and policy stakeholders
Effect of pH and Particle Charge on the Interfacial Properties of Biocatalytic Pickering EmulsionsWhere Are the Enzymes Located?
No full textPickering emulsions (PEs), where water-in-oil (w/o) droplets are stabilized by nanoparticles (NPs), offer a promising platform for biocatalysis by providing a large interfacial area crucial for efficient substrate conversion. While several lipase catalyzed reactions in PEs have been demonstrated, the exact interfacial structure is unknown. This study focuses on the interfacial network formed by NPs and Candida rugosa lipase (CRL) at the octanol/water-interface by varying pH and NP charge. By applying different methods, the location of lipases within a PE was identified and the enzyme concentration profile quantified for the first time. Positively charged nanoparticles (NP+) adsorbed at the o/w-interface together with CRL to form a network-structure. The relation between individual and simultaneous adsorption showed a constant value of 0.75 for the investigated pH range. Negatively charged particles (NP-) did not adsorb spontaneously at the negatively charged octanol/water-interface and therefore showed no influence on the enzyme adsorption behavior. Interfacial shear rheology measurements further revealed distinct elastic behavior of the enzyme–particle network due to attractive interactions between positively charged nanoparticles and CRL. This was shown by a 4.4-fold increase in the interfacial storage modulus. In contrast, repulsive interactionseither between CRL and positively charged particles at low pH or with negatively charged particlesdid not enhance the elastic response of CRL at the interface. Confocal laser scanning microscopy of prepared PE droplets showed an interfacial CRL layer thickness of 0.75 μm for NP+ and 0.51 μm for NP–. Using NP+ results in a 30% higher interfacial enzyme concentration, indicating a more compact layer structure. These insights contribute to optimizing biocatalytic systems using PEs for industrial applications and provide a basis for the quantitative analysis of the interfacial layer in a Pickering emulsion
Enhancing single-cell ATAC sequencing with formaldehyde fixation, cryopreservation, and multiplexing for flexible analysis
No full textObjective: The need for freshly isolated cells in bulk or single cell ATAC-seq experiments creates considerable logistical barriers and increases susceptibility to batch effects. This makes it difficult to coordinate complex or longitudinal studies. Our goal was to develop a sample preservation strategy that overcomes these limitations, enabling consistent and high-quality chromatin accessibility profiling from archived samples.
Results: We established a workflow that incorporates mild formaldehyde fixation prior to cryopreservation, preserving both bulk and single-cell ATAC-seq data quality at levels comparable to fresh samples in HepG2 cells. This protocol reliably maintains key data quality metrics, including signal-to-noise ratio and fragment distributions. Furthermore, the method is fully compatible with transposase-based sample multiplexing using custom Tn5 barcodes. To address barcode hopping inherent to multiplexing, we introduced a computational demultiplexing strategy based on fragment ratios, which accurately assigns single cells to their sample of origin. Our approach streamlines experimental logistics and ensures reproducibility across diverse and temporally dispersed samples, broadening the scope for ATAC-seq–based studies, including those in clinical research settings where coordinated sample collection is challenging
Identifying the Initial Corrosion Fatigue Failure Based on Dropping Electrochemical Potential
No full textThe corrosion fatigue of duplex stainless-steel X2CrNiMoN22-5-3 can be determined by purely alternating axial cyclic load to failure using hour-glass shaped specimens. The experimental setup comprises a corrosion chamber allowing for the circulation of an aquifer electrolyte heated to 369 K simulating a carbon capture and storage as well as geothermal power plant environment. During engineering of a carbon storage site or geothermal power plant, it may be crucial to determine the failure onset of a component beforehand. Therefore, an algorithm with 93.3% reliability was established based on splitting the measured potential values into ten time series with a capacity of ten values. The failure of corrosion fatigue specimens in a geothermal environment correlates to the drop of the curves of the electrochemical potential which is measured simultaneously within the corrosion chamber. Crack initiation was, therefore, successfully derived from the electrochemical potential
User Experience Questionnaire for Workplace Development (UEQ4wave)
No full textDie Entwicklung und Realisierung innovativer Lern- und Arbeitswelten im nationalen und internationalen Kontext führen zu einem Bedarf an Evaluierungsinstrumenten zur Wirkungsanalyse der gebauten Umwelt. Vor diesem Hintergrund wurde ein standardisiertes Evaluierungsinstrument der User Experience (UX) Forschung adaptiert, um eine quantitative Bewertung von Nutzungserlebnissen bei Lern- und Arbeitsumgebungen aus einer mehrdimensionalen Perspektive zu unterstützen. Mit dieser Publikation werden Fragebögen für verschiedene Befragungskontexte und Nutzendengruppen zur Verfügung gestellt, um einen niederschwelligen und ressourcensparenden Einsatz in der Evaluationspraxis von Lern- und Arbeitswelten zu ermöglichen.The development and realization of innovative learning and working environments in a national and international context leads to a need for evaluation instruments to analyze the impact of the built environment. Against this background, a standardized evaluation tool of the user experience (UX) research was adapted to support a quantitative assessment of learning and working environments from a multi-dimensional perspective. This publication provides templates for various survey contexts and user groups (see samples of questionnaires in the appendix) in order to enable a low-threshold and resource-saving use in the evaluation practice of learning and working environments