20005 research outputs found
Sort by
Automated monitoring of organic and bacterial drinking water constitution via PARAFAC fluorescence spectroscopy and flow cytometry
No full textEnsuring high drinking water quality is of major public health concern, protecting consumers from harmful consequences. One relevant concern about drinking water quality is the content of dissolved organic matter (DOM) which can be related to source water quality and treatment needs. Additionally, the bacterial constitution is crucial to monitor evolving changes in time and respond appropriately. However, DOM characterizing methods are a compromise between analytical effort, time and data quality while bacterial methods such as cultivation are labor-intensive, time-consuming and difficult to adapt to online measurements. Therefore, developing an automated monitoring system that quickly and consistently analyzes water quality data with high detail is vital.
This work examines the application of parallel factor analysis (PARAFAC) fluorescence spectroscopy to characterize DOM content and flow cytometry to monitor the presence of bacteria in drinking water. The specific research objectives of this work were mainly to further develop, combine and automate, and test both methods in real-world applications.
Using PARAFAC fluorescence spectroscopy, DOM compositions of investigated drinking waters, originating from groundwater in Northern Germany, were described through a respective fluorescence score of six compounds (C1–C6). Additionally, the total cell count (TCC) and the proportion of high nucleic acid cells (%HNA) were determined via flow cytometry describing the bacterial constitution. Scenarios of water quality changes were simulated in the laboratory by spiking one specific drinking water with increasing amounts of water samples of varying water quality. Water quality could be described by generating parameter-specific baselines defining their thresholds. Strongly deviating waters, e.g., wastewater effluent and rainwater, were identified in lower volume proportions than less strongly deviating waters. Regarding sensitivity, C1–C3 and TCC were the most performant for detecting water quality changes, e.g., due to a contamination event.
Automation of both methods required hardware and software extensions and development. Sampling, data analysis, evaluation, and visualization were the automation objects addressed in this work. In the context of near real-time drinking water analysis, the time required from sampling to data visualization was reduced to less than 15 minutes.
In pilot plant trials utilizing a model drinking water distribution system, combined methods were tested to detect water quality changes in a flowing system. Tests were performed to simulate events of water quality change. The combined system provided characteristic fingerprints of flowing water and detected sudden changes. 300 m behind the injection point, continuous induction of wastewater effluent and rainwater could be detected under appropriate conditions. In a large-scale measurement campaign, a three-component PARAFAC model (c1–c3) was proven to characterize groundwater DOM individually and can be applied to estimate humic substances concentrations in groundwater.
In conclusion, it can be stated that PARAFAC fluorescence spectroscopy in conjunction with flow cytometry represents a rapid and powerful system for the comprehensive characterization of DOM and the presence of bacteria in both drinking water and groundwater. The continuous and automatic monitoring of the emphasized parameters enables to recognize even minor deviations in water characteristics.Die Sicherstellung einer hohen Trinkwasserqualität ist essentiell, um Verbraucher vor gesundheitsschädlichen Folgen zu schützen. Wesentliche Aspekte der Trinkwasserqualität sind der Gehalt an gelösten organischen Substanzen (DOM), der mit der Rohwasserqualität und entsprechender Trinkwasseraufbereitung in Zusammenhang steht, und die bakterielle Konstitution des Trinkwassers. DOM Charakterisierungsmethoden sind jedoch ein Kompromiss zwischen analytischem Aufwand, Zeit und Datenqualität, während bakterielle Methoden wie die Kultivierung arbeitsintensiv, zeitaufwendig und schwer als Online-Messungen zu integrieren sind. Die Entwicklung eines automatisierten Monitoring-Systems, das Wasserqualitätsdaten schnell und konsistent mit hoher Detailgenauigkeit analysiert, ist daher erstrebenswert.
Diese Arbeit untersucht die Anwendung der Fluoreszenzspektroskopie mit paralleler Faktorenanalyse (PARAFAC) zur Charakterisierung des DOM-Gehalts und die Durchflusszytometrie zur Überwachung der Bakterienzahl im Trinkwasser. Die Forschungsziele dieser Arbeit bestanden darin, beide Methoden weiterzuentwickeln, zu kombinieren und zu automatisieren sowie in realen Anwendungen zu testen.
Durch die PARAFAC-Fluoreszenzspektroskopie wurde der DOM-Gehalt der untersuchten Trinkwässer, die aus Grundwasserquellen in Norddeutschland stammten, anhand von sechs Substanzen (C1–C6) mit korrespondierendem Fluoreszenz-Score beschrieben. Mittels Durchflusszytometrie wurden die Gesamtzellzahl (TCC) und der Anteil an Zellen mit hohem Nukleinsäure-Gehalt (%HNA) bestimmt. Im Labor wurden Trinkwasserproben mit zunehmender Konzentration variierender Wässer versetzt um gezielt Wasserqualitätsänderungen zu simulieren. Parameterspezifische Baselines definierten dabei Schwellenwerte der Trinkwasserqualität. Stark abweichende Wässer, z.B. Abwasser und Regenwasser, wurden in geringeren Volumenanteilen erkannt als weniger stark abweichende Wässer. C1–C3 und TCC zeigten die höchste Leistungsfähigkeit bei der Erkennung von Wasserqualitätsänderungen.
Die Automatisierung beider Methoden erforderte Hardware- und Softwareerweiterungen und -entwicklungen. Dabei lag der Fokus auf Probenahme, Datenanalyse, Auswertung und Visua-lisierung beider Methoden. Im Kontext der nahezu Echtzeit-Analyse von Trinkwasser wurde die Zeit von der Probenahme bis zur Datenvisualisierung auf weniger als 15 Minuten verkürzt.
Um Wasserqualitätsänderungen in einem Fließsystem zu erkennen wurden beide Methoden mittels Pilotversuchen in einem Modell-Leitungssystem evaluiert. Dabei wurden gezielt Ereignisse von Wasserqualitätsänderungen simuliert. Das Monitoring-System lieferte charakteristische Fingerabdrücke des fließenden Wassers und erkannte unmittelbare Veränderungen. Zum Beispiel konnte unter gegebenen Bedingungen der Pilotanlage die Einleitung von Abwasser und Regenwasser auch 300 Meter nach der Einleitungsquelle detektiert werden. In einer groß angelegten Messkampagne lag der Fokus auf der Charakterisierung und Quantifizierung von Huminstoffen im Grundwasser. Ein PARAFAC Modell bestehend aus drei Komponenten (c1–c3) erwies sich dafür als geeignet.
Zusammenfassend liefert die PARAFAC-Fluoreszenzspektroskopie in Verbindung mit der Durchflusszytometrie ein schnelles und leistungsfähiges System zur umfassenden Charakterisierung von DOM und Bakterien sowohl im Trinkwasser als auch im Grundwasser. Die kontinuierliche und automatische Überwachung der hervorgehobenen Parameter ermöglicht es, selbst geringfügige Abweichungen in der Wasserqualität zu detektieren.Bundesministerium für Bildung und Forschung (BMBF
Chances of smart Views: Integration of Stakeholder perspectives using videobased Views in MBSE
No full textDie effektive Integration von Stakeholdern spielt eine zentrale Rolle für den
Produktentwicklungserfolg. Im Model-Based Systems Engineering (MBSE) wird der
Informationszugang für Stakeholder ohne MBSE-Erfahrung durch eine formalisierte, abstrakte
Darstellung erschwert und damit das Integrationspotential für Stakeholder vermindert. Zur
Unterstützung der Stakeholder existiert im MBSE das Konzept der Sichtenbildung mit Sichten und
Sichtweisen. Zudem existieren in der Literatur neuartige, smarte Darstellungsformen, die die
Stakeholderintegration ohne formalisierte Diagramme unterstützen. Die intuitive Lesbarkeit
solcher smarten Sichten wurde bisher nicht analysiert. Das Ziel dieser Arbeit ist die Untersuchung
intuitiv lesbarer Darstellungsformen und intelligenter Visualisierungen sowie deren mögliche
Ausgestaltung. Zudem wird der positive Einfluss solcher Visualisierungen – in Form eines Videos –
auf das Systemverständnis von Stakeholdern im Vergleich zu konventionellen, diagrammbasierten
Darstellungen analysiert. In der durchgeführten Laborstudie zeigt sich, dass sich bei der
Anwendung einer smarten Sicht das Systemverständnis bei verringertem Zeitaufwand verbessert.The effective integration of stakeholders plays a central role in the success of
product development. In Model-Based Systems Engineering (MBSE), access to information for
stakeholders without MBSE experience is made more difficult by a formalized, abstract
presentation, thus reducing the integration potential for stakeholders. The concept of view
formation with views and perspectives exists in MBSE to support stakeholders. There are also new,
smart forms of representation in the literature that support stakeholder integration without
formalized diagrams. The intuitive readability of such smart views has not yet been analyzed. The
aim of this thesis is to investigate intuitively readable forms of presentation and smart
visualizations as well as their possible design. In addition, the positive influence of such
visualizations - in the form of a video - on the system understanding of stakeholders is analyzed in
comparison to conventional, diagram-based representations. The laboratory study shows that the
use of a smart view improves system understanding while reducing the time required
Control loop based dimensional error compensation for milling of near-net-shaped, thin-walled structures
No full textAdditive manufacturing has the potential to save resources in the pro-duction of lightweight aerospace structural components made of Ti-6Al-4V. Cur-rently, these components are milled out of plate-material, resulting in up to 95% of the material being converted into chips that can only be downcycled. However, machining near-net-shape parts poses new challenges. For example, commonly used methods such as the “waterline”-path approach, which uses the residual stiff-ness of the plate-material to reduce the deflection of the thin-walls due to process forces, can no longer be applied. In this paper, a dimensional error compensation method is presented, that measures the deflection of the workpiece during helical end mill finishing using eddy current sensors. The sensor values are used within a control loop to adjust the toolpaths width of cut and inclination in real time to minimize dimensional error. Next to adjusting for different compliant states of the workpiece, this method adjusts for increasing tool wear states, that produce higher process forces and thereby larger dimensional errors. The presented compensation is compared to a conventional machining approach to demonstrate its capability to enable finishing of near-net-shape parts within tight tolerances while maintaining high material removal rates
Parameter distribution analysis for enzyme kinetic models with inhibition
No full textThe correct characterization of enzyme kinetics is an important issue for the successful implementation of an enzymatic process on an industrial scale. In this study, the calculation of parameter distribution (PD) based on the known approach of adsorption energy distribution is used to estimate the parameters of different enzyme kinetics with inhibition. For comparison, the parameters are also estimated by nonlinear regression. The results demonstrate that the PD is, in principle, capable of estimating the kinetic parameters of an enzymatic reaction with inhibition. Additionally, the application of this AED-based approach to in silico data demonstrates that the estimated parameters are in better agreement with the set parameters compared to the results obtained through nonlinear regression with a local solver. Furthermore, the efficacy of this approach in estimating kinetic parameters is also evident when it is applied to real experimental data. The successful application of the PD for the estimation of kinetic parameters opens up a further alternative to the multitude of different tools for the characterization of enzyme kinetic parameters. It should be noted that the computational effort is comparatively high. However, this must be considered in the overall context, as this approach requires very few data points and therefore not only can determine kinetic parameters very well but also has the potential to reduce experimental effort in the laboratory
Nonlinear viscoelasticity of and structural modulation in guar gum-enhanced triple-network hydrogels
No full textThe effect of the presence of guar gum (0–0.75 wt%) in a thermo-responsive triple-network (TN) PVA/TA/PVA-MA-g-PNIPAAm hydrogel (PVA: polyvinyl alcohol; MA: methacrylate, PNIPAAm: poly-N-isopropyl acryl amide; TA: tannic acid) with respect to the structural, mechanical, and viscoelastic properties was mapped. A comprehensive analysis, using large-amplitude oscillatory shear (LAOS), SEM imaging, XRD, and mechanical analysis revealed that guar enhances hydrogel crystallinity (up to 30% at 0.75 wt%), which goes along with a strain hardening. The hydrogel achieved superior mechanical performance at a gum concentration of 0.5 wt% with a 40% increase in shear-thickening, an enhanced strain tolerance in nonlinear regimes, and a good mechanical robustness (maximum elongation to break of 500% and stress of 620 kPa). The hydrogel with 0.5 wt% guar exhibited also a good thermal response (equilibrium swelling ratio changed from 8.4 at 5 °C to 2.5 at 50 °C) and an excellent thermal cycling dimensional stability. Higher guar concentrations reduce structural resilience, leading to brittle hydrogels with lower extensibility and viscoelastic stability
Supercritical CO2 extraction of bioactives from P. halepensis petals: Process modeling, mass transfer, and bioactivity characterization
No full textThe extraction of bioactive compounds from P. halepensis petals was carried out using supercritical carbon dioxide (Sc-CO2) under varying operational conditions, including extraction time, pressure (300–500 bar), co-solvent type (water or ethanol), and particle size (120–1400 µm), and compared to conventional techniques such as Soxhlet extraction and maceration. The results showed that Sc-CO2 extraction at 300–500 bar achieves ∼80 % recovery of bioactive compounds within the first 30 min. Tan, Liang and Liou model successfully fitted the extraction kinetics. Furthermore, all extracts demonstrated moderate to high anticancer activity against LS174t and HCT116 cell lines compared to tamoxifen (a well-known anticancer standard). Extracts obtained by Sc-CO2 with water as a co-solvent exhibited significant antioxidant activity against DPPH free radical; however, their antioxidant activities were notably lower than those obtained through conventional extraction methods. Finally, 38 molecules were identified by HPLC-DAD and 24 by GC-MS. The originality and novelty of this study are a) First-time application of Sc-CO2 to extract bioactive compounds from P. halepensis petals; b) Identification of new chemical compounds (seven detected for the first time in this species) as a novel contribution
A review on aging effects of thermoset prepregs
No full textThermoset prepreg materials have emerged as the composite material of choice for demanding structural applications due to their easy processability and attainable superior part quality. However, the one-part nature of common precured thermoset resins renders prepregs susceptible to undesired premature curing, which may entail deterioration of properties. This article reviews the current state of literature on thermoset prepregs with regard to aging effects that originate before the final cure cycle of composite parts, i.e., during freezer storage and upon temporary storage or processing at room temperature. Therefore, the aging-related evolution of the physio-chemical prepreg state (conversion, Tg, water uptake, viscosity) is examined in terms of its impact on processing (forming properties, tack), applied cure cycles (temperature, dwell time, pressure) and post-cure laminate quality (porosity, mechanical performance). The economic and ecological implications of prepreg aging are discussed in conjunction with recycling strategies for out-of-spec material. Finally, approaches proposed to mitigate out-time effects of prepregs (latent curing agents, cure cycle modification, vitrimer matrices) are presented
Electrified distillation – optimized design of closed cycle heat pumps with refrigerant selection and flash-enhanced mechanical vapor recompression
No full textImproving the energy efficiency of distillation processes is crucial for reducing the high energy demand and environmental impact of the chemical industry. Compression heat pumps play a significant role in this transformation as they are able to upgrade and recover heat rejected at low temperatures, reducing the need for external heat sources and simultaneously enable process electrification. Mechanical vapor recompression is the most prominent heat pump concept in distillation but limited by its reliance on process streams, which can lead to high external heat demand, or even inapplicability of the concept due to thermal instability or mechanical compressor limitations. Closed cycle heat pumps are less explored, since they require an extra heat exchanger and increased temperature lift compared to mechanical vapor recompression. However, they can overcome some of the limitations by allowing for unrestricted selection of the most attractive refrigerant, which may outplay the structural disadvantages. The current study presents a novel design approach for rapid heat pump evaluation, applicable to any subcritical refrigerant solely based on temperature levels and duties. A two-step approach enables the identification of the best-performing refrigerant from a set of suitable candidates for a given distillation process, considering practical constraints such as the need for superheating to avoid condensation, as well as limits for the compressor discharge temperature and compression ratios. The most promising refrigerant and heat pump configuration is further evaluated by a techno-economical optimization based on a superstructure model for which the performance is compared with a novel mechanical vapor recompression design utilizing a vapor recycle and internal preheating. The optimization results not only showcase fully electrified distillation for all heat pump-assisted processes but also highlight that closed cycle heat pumps with proper refrigerant selection can provide significant energy and cost savings while clarifying the respective advantages and limitations of competing concepts
The energy aggregator problem – a holistic mixed-integer linear programming approach
No full textIn this paper, a new mixed integer linear programming (MILP) model for the day-ahead operation of energy aggregators (EA) is developed. Synergies between the different types of flexibility and energy trading options enable EAs in decentralized and renewable energy systems to provide economic benefits to participating households but require a detailed consideration of technological properties and constraints of the respective types of resources. Therefore, the main contribution of this work is the development of a new EA model (EAM), which combines a holistic perspective with a high level of technical detail to better address the complexity of the EA decision. Most importantly, power-to-heat systems are integrated with their inherent thermal relations between heat pumps, heater rods and heat storages. In combination with other energy resources such as photovoltaic systems, electric vehicles, household battery storages and time-shiftable loads, households are modeled as systems with interdependent electrical power and heat flows. Moreover, three different trading levels (wholesale, local markets and internal trading) are taken into account. The model application to a case study with up to 111 individually modeled prosumer households in a summer and a winter scenario reveals high synergetic potential of EAs resulting from the flexibility of multiple trading options in combination with the flexibility of various energy resources. The results validate the efficacy of the model, as significant economic benefits for households are realized in comparison to a base case of non-aggregated households, showing that the three trading levels significantly contribute to these benefits. Further analyses give insights into the interdependent synergetic relations between different flexible resources, underlining the importance of a holistic optimization approach that explicitly takes these relations into account. For future research, the EAM is proposed as a base model to depict the behavior of EAs
Introduction of a system Definition in the Common Parametric Aircraft Configuration Schema (CPACS)
No full textThe aircraft design process is a complex task that requires the collaboration of disciplinary experts from various fields. In practice, this complexity requires a large investment in setting up communication interfaces for the exchange of disciplinary data, and serious misinterpretations are not uncommon. To increase the efficiency and robustness of data exchange, a common language is essential. As such, the Common Parametric Aircraft Configuration Schema (CPACS) serves as a central data model, which currently includes detailed parametrizations of aircraft geometry and analysis results from traditional disciplines (e.g., aerodynamics, structure, etc.). However, with the recent interest in alternative propulsion and complex on-board system architectures, CPACS is proving to be too limited to meet the needs of the various disciplinary system experts. The particular challenge here is to enable different views on the same systems, i.e., a functional/logical as well as a geometric/physical representation, without violating the principle of unambiguous data. Therefore, this paper proposes an extension of CPACS which introduces an explicit system definition covering both representations. Its potential is demonstrated by two use cases from disciplinary experts in the field of on-board system design at the Hamburg University of Technology (TUHH), based on data provided by aircraft design experts. Through validation against the experts’ needs, the proposed system definition proves to bridge the gap between preliminary aircraft design and on-board system design, enabling a holistic, robust and efficient aircraft design process