Accuracy assessment of simplified computation of active and passive magnetic shielding for optically pumped magnetometers. - In: IEEE transactions on magnetics, ISSN 1941-0069, Bd. 58 (2022), 9, 7401204, insges. 4 S.
A low residual environmental magnetic field is required for the proper operation of most optically pumped magnetometers (OPMs). This is achieved using a combination of passive and active magnetic shielding. Passive magnetic shielding often uses multiple layers of highly permeable materials. A realistic two-layer magnetically shielded room (MSR) for biomagnetic measurements is numerically studied using the finite element method. A measured B-H characteristic of Mumetal is used, which is linearly extrapolated from the Rayleigh region (RR) into the low magnetic field range. This extension of the magnetization curve yields no significant differences compared to using a constant permeability value for the low magnetic field range. Furthermore, we model the MSR with only one shield and apply a simple analytical method of images (MOI). The MOI yields on average a 100-fold reduction in computation time. The relative difference of the magnetic flux density computed with MOI and finite element method (FEM) is smaller than < 1% at the center of a spherical region of interest (ROI) with a radius of 0.3 m desired from the point of magnetoencephalography (MEG) using OPMs. The achieved accuracy of the MOI makes it suitable for the optimization of active shielding coils.
https://doi.org/10.1109/TMAG.2022.3161736
The potential of multispectral imaging flow cytometry for environmental monitoring. - In: Cytometry, ISSN 1552-4930, Bd. 101 (2022), 9, S. 782-799
Environmental monitoring involves the quantification of microscopic cells and particles such as algae, plant cells, pollen, or fungal spores. Traditional methods using conventional microscopy require expert knowledge, are time-intensive and not well-suited for automated high throughput. Multispectral imaging flow cytometry (MIFC) allows measurement of up to 5000 particles per second from a fluid suspension and can simultaneously capture up to 12 images of every single particle for brightfield and different spectral ranges, with up to 60x magnification. The high throughput of MIFC has high potential for increasing the amount and accuracy of environmental monitoring, such as for plant-pollinator interactions, fossil samples, air, water or food quality that currently rely on manual microscopic methods. Automated recognition of particles and cells is also possible, when MIFC is combined with deep-learning computational techniques. Furthermore, various fluorescence dyes can be used to stain specific parts of the cell to highlight physiological and chemical features including: vitality of pollen or algae, allergen content of individual pollen, surface chemical composition (carbohydrate coating) of cells, DNA- or enzyme-activity staining. Here, we outline the great potential for MIFC in environmental research for a variety of research fields and focal organisms. In addition, we provide best practice recommendations.
https://doi.org/10.1002/cyto.a.24658
Back to the Roots - Bewertung und Vergleich der Nachhaltigkeit von Nahrungsmitteln im Lebensmitteleinzelhandel : Abschlussbericht für die Deutsche Bundesstiftung Umwelt. - Ilmenau. - 1 Online Ressource (37 Seiten)Literaturverzeichnis: Seite 34-36
Gegenwärtig ist es nahezu unmöglich die vielfältigen Nachhaltigkeitsleistungen von Lebensmitteln einzusehen oder zu vergleichen, da Informationen über die gesamte Prozesskette nicht umfänglich verfügbar sind. Um das steigende Informationsinteresse der Konsumierenden zu bedienen und damit einen verantwortungsvollen Konsum (Ziel 12 der Sustainable Development Goals, UN 2016) von Lebensmitteln zu ermöglichen, sollten entsprechende Informationen in einer übersichtlichen Form am point of sale für die Verbraucher_innen verfügbar sein. Vor diesem Hintergrund entwickelten wir im Projekt einen Bewertungsansatz und darauf aufbauend eine mobile App, welche eine produktspezifische Ausweisung von Nachhaltigkeitsinformationen (Fokus: Umwelt + Gesundheit) beim Einkauf ermöglicht.
http://www.dbu.de/OPAC/ab/DBU-Abschlussbericht-AZ-33981_01-Hauptbericht.pdf
Establishing an experimental and simulation interface for online monitoring and modeling of bacterial growth in water distribution systems. - In: Adaptive planning and design in a age of risk and uncertainty, (2022), S. 1123-1131
Water distribution systems (WDSs) function to deliver high-quality water in major quantities. While standard water quality parameters are monitored at waterworks, it is still a challenge to monitor water quality in the WDS network itself. Only hydraulic parameters are frequently monitored and modeled in drinking water networks in Germany. Moreover, the majority of German drinking water utilities does not disinfect when the product leaves the waterworks. This is also common practice in Northern European countries. It is thus important to monitor specific organic and bacteriological water quality parameters which define the system state. This study develops an experimental and simulation integrated framework for continuously monitoring and simulating selected organic and bacteriological water quality parameters, so abnormal deviations in water quality behavior can be detected and responded to in real time. A simple reproducible bacteria regrowth model was taken to initialize the validation of experimental values in a water quality model simulation. Batch experiment measurements from a flow cytometer are analyzed to establish an interface between laboratory values and water quality simulations. Monod kinetics are utilized to describe the bacterial growth rate according to the respective substrate for modeling the bulk species in the water network. Experimental values are incorporated in the simulations for validation. The simulation of bacterial growth is conducted firstly on a network model of a real-life test bed and on various selected distribution system models of different sizes and complexities. First results of the water quality simulations show a successful transition of experimental analysis into water quality simulations and give a promising outlook for developing an online-monitoring and prediction methodology for detecting water quality anomalies efficiently in real time.
Real-time monitoring and controlling of water quality in water distribution networks based on flow cytometry and fluorescence spectroscopy. - In: Adaptive planning and design in a age of risk and uncertainty, (2022), S. 1155-1167
Guaranteeing the high-quality of water in water distribution networks (WDSs) is a priority when it comes to ensuring public health. Since the majority of German water utilities (and also other EU countries) do not chlorinate, controlling of nutrients in WDSs such as assimilable organic carbon (AOC) and monitoring of microbiological activities is indispensable. Conventional methods to characterize microbiological activity and dissolved organic matter are time-consuming and labor-intensive. This study presents data on flow cytometry and fluorescence spectroscopy as leading-edge technologies for real-time analysis of drinking water quality in WDS. Flow cytometry is a sensitive method which can be applied in online modus for accurate detection of bacterial cell numbers. Furthermore, fluorescence spectroscopy is a rapid and quantitative technique for detailed characterization of dissolved organic carbon (DOC) including fractions of natural organic matter (NOM). The integration of both techniques is promising for real-time water quality analysis and as a supporting tool for quality control. In the initial step of this research, an experimental laboratory setup of simultaneous analysis is developed. Thus, the goal is to achieve knowledge about possible relations between water quality parameters, more precisely bacterial regrowth potential and the character of dissolved organic constituents. In continuous measurements, the initial state of microbiological growth is to be determined based on flow cytometric data. Due to fluorescence spectroscopy data the microbiological regrowth potential will be predicted. This will be achieved by online detecting of certain organic fractions of the DOC which can be utilized as nutrients by present bacteria. The overall project goal is the establishing of an interface between monitoring parameters and water quality simulation models for the WDSs. First promising results show the successful utilization of adapted AOC as regrowth potential parameter, which can be used for water quality simulations in a WDS.
Optimal control of chlorine concentration in water distribution system. - In: Adaptive planning and design in a age of risk and uncertainty, (2022), S. 1146-1154
Supplying high-quality water is the key task of water distribution systems (WDSs). Although in Germany and some other countries chlorine is no longer used, it remains as a major disinfectant in WDSs worldwide. Therefore, chlorine concentration represents an important parameter for determining the water quality; that is, we should ensure the chlorine concentration within a reasonable range in a WDS. However, due to the complexity of the network structure and nonlinear behavior of the system, the control of chlorine concentration in WDSs imposes a challenging task. In this study, a model-based optimal control strategy is developed to address this problem. The mass and energy conservation laws are used to describe the hydraulic properties of WDSs. The one-dimensional advective transport model is simplified to describe the decay of chlorine in the pipelines. The chlorine concentration limits at the nodes are formulated as inequality constraints which will be satisfied by manipulating the flows and their directions in the pipelines. As a result, a nonlinear optimization problem is formulated and solved to achieve the specified chlorine concentration. For verifying our approach, we deliver the computed results for benchmark networks as input to the simulation model in EPANET, and the simulation gives satisfactory values of the specified chlorine concentration in the network.
Hydra: practical metadata security for contact discovery, messaging, and voice calls. - In: SN Computer Science, ISSN 2661-8907, Bd. 3 (2022), 5, 341, insges. 22 S.
Protecting communications’ metadata can be as important as protecting their content, i.e., recognizing someone contacting a medical service may already allow to infer sensitive information. There are numerous proposals to implement anonymous communications, yet none provides it in a strong (but feasible) threat model in an efficient way. We propose Hydra, an anonymity system that is able to efficiently provide metadata security for a wide variety of applications. Main idea is to use latency-aware, padded, and onion-encrypted circuits even for connectionless applications. This allows to implement strong metadata security for contact discovery and text-based messages with relatively low latency. Furthermore, circuits can be upgraded to support voice calls, real-time chat sessions, and file transfers - with slightly reduced anonymity in presence of global observers. We evaluate Hydra using an analytical model as well as call simulations. Compared to other systems for text-based messaging, Hydra is able to decrease end-to-end latencies by an order of magnitude without degrading anonymity. Using a dataset generated by performing latency measurements in the Tor network, we further show that Hydra is able to support anonymous voice calls with acceptable quality of service in real scenarios. A first prototype of Hydra is published as open source.
https://doi.org/10.1007/s42979-022-01231-9
Nonlinear control for rapid and nonovershooting voltage regulation of the Double Buck Converter. - In: 2022 IEEE 17th International Conference on Control & Automation (ICCA), (2022), S. 838-843
We propose a novel nonlinear control method for the voltage regulation of a buck converter to achieve a rapid and nonovershooting step response. The method combines feedback linearisation with a linear static state feedback controller to shape the system transient response. Experimental results involving performance comparisons with conventional linear controllers show the proposed method can deliver substantial improvement in the step reference response of a buck converter circuit, while also providing improved transient response in the rejection of both line and load disturbances.
https://doi.org/10.1109/ICCA54724.2022.9831810
A new measurement method of contact conditions in a vacuum circuit breaker with the field emission current during the closing operation. - In: IEEE transactions on instrumentation and measurement, ISSN 0018-9456, Bd. 71 (2022), 6005111, insges. 11 S.
The performance of vacuum circuit breakers (VCBs) in the interruption and protection of an electric power system is highly dependent on the contact conditions; thus, the assessment of the contact conditions is essential. The field emission current has been recognized as an effective parameter with which to investigate the contact conditions both qualitatively and quantitatively. The traditional measurement method that uses the field emission current to determine the contact conditions is performed under ac voltage and requires the VCB to be dismantled, which limits the application of this method. The objective of this study is to develop a new measurement method for the contact conditions in a VCB with the field emission current during the closing operation under dc voltage. The new measurement method does not require the VCB to be dismantled and can simplify the processing of experimental data. Then, the new measurement method is applied to investigate the contact conditions during capacitive switching. The obtained result shows that the field enhancement factor $\beta $ of the contact surface oscillates up and down during the capacitive experiment, which can verify the conditioning and deconditioning effects of the inrush current on contact surfaces.
https://doi.org/10.1109/TIM.2022.3193710
Set-point tracking for nonlinear systems subject to uncertainties using model-following control with a high-gain controller. - In: 2022 European Control Conference (ECC), (2022), S. 1617-1622
We study the robust control problem for nonlinear systems using a model-following control (MFC) scheme. The MFC architecture is a two degrees-of-freedom structure consisting of two control loops: the model control loop (MCL) including a nominal model of the process, and the process control loop (PCL) accounting for modelling errors and disturbances. Both control loops are designed using (partial) feedback linearisation. We design a set-point controller in the MCL and apply a high-gain state feedback in the PCL. We analyse the stability of the overall system and derive robustness bounds for a class of locally Lipschitz uncertainties. We analyse and compare robustness and performance properties to various different control designs. It turns out that the proposed controller is able to stabilise significantly larger uncertainties, while requiring less control effort and shows better tracking performance.
https://doi.org/10.23919/ECC55457.2022.9838162