Hochschule für Technik FHNW

Permanent URI for this community

https://irf.fhnw.ch/handle/11654/35

Browse

Now showing 1 - 20 of 592

Fast and efficient estimation of resonant modes. A case study of mechanical drivelines
(Institut für Elektrische Energietechnik, Hochschule für Technik FHNW, 28.08.2024) Rezaeizadeh, Amin; Mastellone, Silvia
This work presents the development of an online parameter estimation algorithm for the identification of resonating modes in a linear system of arbitrary order. The method employs a short-time Fourier transform of the input and output signals and uses a recursive least square (RLS) algorithm to detect resonant frequencies and damping factors of the resonant modes.
05 - Forschungs- oder Arbeitsbericht
Do MCH prisms change asthenopic complaints when reading?
(DOZ-Verlag, 28.06.2024) Joss, Joëlle; Jainta, Stephanie [in: Optometry & Contact Lenses]
Purpose. Asthenopic symptoms mostly occur during demanding near-sighted tasks and are related to binocular symptoms (e.g. heterophoria), among others. Correction of symptomatic heterophoria with prismatic glasses is one way to treat the symptoms. This study investigates the effect of wearing a horizontal prismatic correction for 6 months. Material and Methods. A total of 87 subjects were assigned to a heterophoric prism group (N=32), a heterophoric control group (N= 31) or an orthophoric control group (N= 24) according to their MCH heterophoria. In the heterophoric prism group, the subjects were prescribed glasses with a prismatic correction for 6 months according to their distance correction; in contrast, the subjects in the heterophoric control group had to wear glasses without prismatic correction for the same period. The effect of the prisms on complaints due to asthenopic symptoms was investigated by comparing the total sum obtained in the CISS questionnaire at the beginning of the study and after 6 months (before and after wearing glasses) for the 3 groups. Results. A (long-term) prism effect was not apparent in the CISS total score. In both the heterophoric prism group and in the heterophoric control group, the CISS total score increased slightly and non-significantly after 6 months. When considering the heterophoric subjects with an increased CISS score at baseline, a nevertheless slight but non-significant decrease of symptoms was observed. All changes were observed in both the heterophoric prism group and the heterophoric control group. An additional analysis using binocular profiles showed a reduction in symptoms by numbers and specifically for subjects with reduced vergence facility. Conclusion. Wearing an individual, horizontal prismatic correction had no effect on the overall CISS-score for our test subjects. Further methods that allow a systematic recording of symptoms and optometric parameters are probably necessary to observe an effect. These could be binocular profiles that classify individuals according to their binocular parameters.
01A - Beitrag in wissenschaftlicher Zeitschrift
Tätigkeitsbericht 2023
(Institut für Automation, Hochschule für Technik FHNW, 04.04.2024) Isler, Rolf; Gabrys, Jadwiga
Tätigkeitsberichte über aktuelle Forschungsprojekte, die im Institut im Jahr 2023 bearbeitet wurden.
05 - Forschungs- oder Arbeitsbericht
Energyefficient Kubernetes
(Hochschule für Technik FHNW, 22.03.2024) Baur, Jérôme; Engel, Julie; Graf, Sebastian; SIX Group
Cloud Computing hat sich als unverzichtbarer Bestandteil der IT-Welt etabliert. Es ermöglicht Unternehmen, Ressourcen wie CPU und Arbeitsspeicher flexibel und bedarfsgerecht zu nutzen. Eine eziente Nutzung dieser Ressourcen ist entscheidend, da eine ineziente Nutzung mit einem erhöhten Stromverbrauch einhergeht. Bei der Produktion von Strom werden, direkt oder indirekt, Treibhausgase emittiert. Aufgrund des kontinuierlichen und starken Wachstums von Kubernetes als Schlüsseltechnologie besteht ein erhebliches Potenzial, die CO2-Emissionen durch eine ezientere Nutzung dieser Plattform zu reduzieren. Diese Arbeit untersucht den Energieverbrauch von Kubernetes-Clustern mithilfe des KeplerProjektes und zielt darauf ab, Strategien zur Steigerung der Energieezienz zu identifizieren und zu bewerten. Im Zentrum stehen dabei zwei Hauptansätze: der Vergleich von Monolithen und Microservices hinsichtlich ihres Energieverbrauchs und die Evaluation des Einsatzes des Vertical Pod Autoscalers (VPA) zur Optimierung der Ressourcennutzung. In der Untersuchung des ersten Ansatzes wurde festgestellt, dass die Deploymentstrategie (Monolith vs. Microservices) allein keine signifikante Auswirkung auf die Energieezienz hat. Der Energieverbrauch wird hauptsächlich durch den Idle Energieverbrauch der Nodes beeinflusst. Der zweite Ansatz dieser Arbeit, der Einsatz des Vertical Pod Autoscalers, zeigte hingegen positive Eekte auf die Energieezienz. Durch die dynamische Anpassung der Ressourcenanforderungen von Pods und durch das Entfernen von Nodes konnte die Auslastung der Nodes verbessert und somit der Idle Energieverbrauch verringert werden. Dies führte zu einer signifikanten Reduktion des Energieverbrauchs. Diese Arbeit bietet wichtige Einsichten in die Energieezienz von Kubernetes-Clustern und zeigt auf, dass insbesondere die Reduktion des Idle Energieverbrauchs und der gezielte Einsatz von Ressourcenmanagement-Tools entscheidend für ezientere Ressourcennutzung sind.
11 - Studentische Arbeit
Air cleaners and respiratory infections in schools. A modeling study using epidemiological, environmental, and molecular data
(Oxford University Press, 30.12.2023) Banholzer, Nicolas; Jent, Philipp; Bittel, Pascal; Zürcher, Kathrin; Furrer, Lavinia; Bertschinger, Simon; Weingartner, Ernest; Ramette, Alban; Egger, Matthias; Hascher, Tina; Fenner, Lukas [in: Open Forum Infectious Diseases]
AbstractBackgroundUsing a multiple-measurement approach, we examined the real-world effectiveness of portable HEPA-air filtration devices (air cleaners) in a school setting.MethodsWe collected environmental (CO2, particle concentrations), epidemiological (absences related to respiratory infections), audio (coughing), and molecular data (bioaerosol and saliva samples) over seven weeks during winter 2022/2023 in two Swiss secondary school classes. Using a cross-over study design, we compared particle concentrations, coughing, and the risk of infection with vs without air cleaners.ResultsAll 38 students (age 13−15 years) participated. With air cleaners, mean particle con-centration decreased by 77% (95% credible interval 63%−86%). There were no differences in CO2levels. Absences related to respiratory infections were 22 without vs 13 with air cleaners. Bayesian modeling suggested a reduced risk of infection, with a posterior probability of 91% and a relative risk of 0.73 (95% credible interval 0.44−1.18). Coughing also tended to be less frequent (posterior probability 93%). Molecular analysis detected mainly non-SARS-CoV-2 viruses in saliva (50/448 positive), but not in bioaerosols (2/105 positive) or HEPA-filters (4/160). The detection rate was similar with vs without air cleaners. Spatiotemporal analysis of positive saliva samples identified several likely transmissions.ConclusionsAir cleaners improved air quality, showed a potential benefit in reducing respiratory infections, and were associated with less coughing. Airborne detection of non-SARS-CoV-2 viruses was rare, suggesting that these viruses may be more difficult to detect in the air. Future studies should examine the importance of close contact and long-range transmission, and the cost-effectiveness of using air cleaners.
01A - Beitrag in wissenschaftlicher Zeitschrift
A novel measurement system for unattended, in situ characterization of carbonaceous aerosols
(Copernicus, 22.12.2023) Keller, Alejandro; Specht, Patrick; Steigmeier, Peter; Weingartner, Ernest [in: Aerosol Research]
Carbonaceous aerosol is a relevant constituent of the atmosphere in terms of climate and health impacts. Nevertheless, measuring this component poses many challenges. There is currently no simple and sensitive commercial technique that can reliably capture its totality in an unattended manner, with minimal user intervention, for extended periods of time. To address this issue we have developed the fast thermal carbon totalizator (FATCAT). Our system captures an aerosol sample on a rigid metallic filter and subsequently analyses it by rapidly heating the filter directly, through induction, to a temperature around 800°C. The carbon in the filter is oxidized and quantified as CO2 in order to establish the total carbon (TC) content of the sample. The metallic filter is robust, which solves filter displacement or leakage problems, and does not require a frequent replacement like other measurement techniques. The limit of detection of our system using the 3σ criterion is TC =0.19 µg-C (micrograms of carbon). This translates to an average ambient concentration of TC =0.32 µg-C m^−3 and TC =0.16 µg-C m^−3 for sampling interval of 1 or 2 h respectively using a sampling flow rate of 10 L min^−1. We present a series of measurements using a controlled, well-defined propane flame aerosol as well as wood-burning emissions using two different wood-burning stoves. Furthermore, we complement these measurements by coating the particles with secondary organic matter by means of an oxidation flow reactor. Our device shows a good correlation (correlation coefficient, R^2>0.99) with well-established techniques, like mass measurements by means of a tapered element oscillating microbalance and TC measurements by means of thermal–optical transmittance analysis. Furthermore, the homogeneous fast-heating of the filter produces fast thermograms. This is a new feature that, to our knowledge, is exclusive of our system. The fast thermograms contain information regarding the volatility and refractoriness of the sample without imposing an artificial fraction separation like other measurement methods. Different aerosol components, like wood-burning emissions, soot from the propane flame and secondary organic matter, create diverse identifiable patterns.
01A - Beitrag in wissenschaftlicher Zeitschrift
Quantum logical controlled-NOT gate in a lithium niobate-on-insulator photonic quantum walk
(Institute of Physics Publishing, 17.11.2023) Chapman, Robert J; Häusler, Samuel; Finco, Giovanni; Kaufmann, Fabian; Grange, Rachel [in: Quantum Science and Technology]
The two-qubit controlled-NOT gate is one of the central entangling operations in quantum information technology. The controlled-NOT gate for single photon qubits is normally realized as a network of five individual beamsplitters on six optical modes. Quantum walks (QWs) are an alternative photonic architecture involving arrays of coupled waveguides, which have been successful for investigating condensed matter physics, however, have not yet been applied to quantum logical operations. Here, we engineer the tight-binding Hamiltonian of an array of lithium niobate-on-insulator waveguides to experimentally demonstrate the two-qubit controlled-NOT gate in a QW. We measure the two-qubit transfer matrix with 0.938 ± 0.003 fidelity, and we use the gate to generate entangled qubits with 0.945 ± 0.002 fidelity by preparing the control photon in a superposition state. Our results highlight a new application for QWs that use a compact multi-mode interaction region to realize large multi-component quantum circuits.
01A - Beitrag in wissenschaftlicher Zeitschrift
Development of a waveguide-based interferometer for the measurement of trace substances
(Zenodo, 07.11.2023) Weingartner, Ernest; Bilal, Jonas; Steigmeier, Peter; Jundt, Gregor; Häusler, Samuel; Lenner, Miklós; Flöry, Nikolaus; Bittner, Matthias; Betschon, Felix
Photonic integration on a chip has the potential to develop new low-cost, high-performance sensing devices. A proof of concept of the sensing capabilities of a waveguide-based photothermal interferometer for the measurement of traces of light-absorbing substances (soot particles, gases) has been achieved. The measurement principle can also be extended to a wide range of other applications such as refractive index measurements, or vibration/distance sensors. A unique feature is that the waveguide technology allows for a passive operation of the interferometer, i.e., no quadrature point control is required.
04B - Beitrag Konferenzschrift
Multiscale characterisation of staple carbon fibre-reinforced polymers
(MDPI, 06.11.2023) Zweifel, Lucian; Kupski, Julian; Dransfeld, Clemens; Caglar, Baris; Baz, Stephan; Cessario, Damian; Gresser, Götz T.; Brauner, Christian [in: Journal of Composites Science]
The aim of this study was to characterise the microstructural organisation of staple carbon fibre-reinforced polymer composites and to investigate their mechanical properties. Conventionally, fibre-reinforced materials are manufactured using continuous fibres. However, discontinuous fibres are crucial for developing sustainable structural second-life applications. Specifically, aligning staple fibres into yarn or tape-like structures enables similar usage to continuous fibre-based products. Understanding the effects of fibre orientation, fibre length, and compaction on mechanical performance can facilitate the fibres’ use as standard engineering materials. This study employed methods ranging from microscale to macroscale, such as image analysis, X-ray computed tomography, and mechanical testing, to quantify the microstructural organisations resulting from different alignment processing methods. These results were compared with the results of mechanical tests to validate and comprehend the relationship between fibre alignment and strength. The results show a significant influence of alignment on fibre orientation distribution, fibre volume fraction, tortuosity, and mechanical properties. Furthermore, different characteristics of the staple fibre tapes were identified and attributed to kinematic effects during movement of the sliver alignment unit, resulting in varying tape thicknesses and fuzzy surfaces.
01A - Beitrag in wissenschaftlicher Zeitschrift
Interactive use-case generation tool for functional REST API testing
(Hochschule für Technik FHNW, 18.08.2023) Volken, Jonas; Leu, Benjamin; Kropp, Martin; Affolter, Fabian; Tesitifi GmbH
Software is an integral part of any business, which makes the significance of high-quality software in today’s digital age undeniable. However, despite the advancements in software testing, challenges persist in efficiently planning, generating, and executing test cases, particularly for REST API-based applications. This project addresses the issue by developing a sequence generator tool that enables testers to effortlessly create and execute sequences of requests, streamlining the creation of comprehensive test scenarios. By simplifying the process of connecting response values to subsequent request values, the software seeks to maximize test coverage, improve test quality, and enable testers to focus more on software quality enhancement than the efforts of test construction. The client for this project is Testifi GmbH, a company dedicated to enhancing software delivery processes through DevOps integrations and AI-automated quality assurance solutions. The main focus of the project was to find out if the test quality increased by using the sequence generator tool due to more edge cases and more complex scenarios being tested compared to manual API testing, as well as showing if the efficiency improvement can be measured in reduced amount of time necessary for creation sequences. To answer these questions and develop an application that offers value for Testifi GmbH, a literature review was conducted on the subjects of basic user interface design and user experience concepts for advanced users. Based on the findings, the user interface of the application was outlined and the software implemented. During development and with the finished product, multiple sets of user tests were conducted with users experienced in working with APIs, to improve the design and software during development, and to gain insights about the effectiveness of the final product. Those tests showed that the main goals of the project could be reached by demonstrating a considerable amount of time saved by using the application, while also outperforming manual testing methods in efficiency and ease of use. Key features like the linking of response values to subsequent request values and the suggestion of such links based on Testifi’s Pulse Artificial intelligence (AI) as well as previously created sequences were well received by testers and customer. The literature review also proved to be very valuable as users praised the straightforward design, while never missing any important data. When Testifi GmbH integrates the end product in their pulse workflow, its ability to create sequences easily and intuitively as well as the potential of the additional link suggestions created by the tool to be used in improving the Pulse AI will be indispensable.
11 - Studentische Arbeit
Tailored flexibility in inherently brittle epoxy-based composites through gradient interphase formation with bio-based thermoplastic elastomer grades
(Elsevier, 05.07.2023) Zweifel, Lucian; Kupski, Julian; Brauner, Christian [in: Composites Part A: Applied Science and Manufacturing]
This study focuses on tailoring elastic behaviour in an inherently brittle epoxy-based fibre-reinforced composite material formed through a gradient interphase with a bio-based thermoplastic elastomer. The fast-curing epoxy Araldite LY3585/Aradur 3475 was tested with two bio-based Pebax block copolymer grades. First, the interphase was characterised via optical hot-stage microscopy and Raman spectroscopy. The analysis unveiled pronounced diffusion followed by a reaction-induced phase separation, which led to the formation of an interphase with a thickness exceeding 200 μm at the temperatures associated with the curing process. Second, composite laminates were fabricated through a combined process of fused filament fabrication and vacuum infusion, incorporating a flexible domain with variable stiffness properties. The material architecture exhibited brittle-to-ductile behaviour at the micrometre scale, with tailored flexible response under bending and stiff behaviour in tension. Consequently, the study anticipates using multi-scale toughened material structures for more efficient generative design concepts.
01A - Beitrag in wissenschaftlicher Zeitschrift
Tätigkeitsbericht 2022
(Institut für Automation, Hochschule für Technik FHNW, 04/2023) Isler, Rolf; Gabrys, Jadwiga
Tätigkeitsberichte über aktuelle Forschungsobjekte, die im Institut im Jahr 2022 bearbeitet wurden
05 - Forschungs- oder Arbeitsbericht
Maintenance and evolution of large scale software systems – Business, dev & ops challenges
(10.02.2023) Rüegger, Janick; Kropp, Martin
Even in the time of agile software development and devOps, maintenance and evolution of large-scale software systems remain challenging. This is not only caused by technical debt, but is heavily caused by lost knowledge, high complexity of micro-service architectures, difficult requirements management, not available documentation, and the complexity of communication among and coordination of the many stakeholders. In our session we will talk about the challenges we identified in our study and present new approaches to address these challenges.
06 - Präsentation
Investigation of flow fields emanating from two parallel inlet valves using LES, PIV, and POD
(MDPI, 2023) Hoffmann, Jana; Vera Tudela, Walter; Mirsch, Niklas; Wüthrich, Dario; Schneider, Bruno; Günther, Marco; Pischinger, Stefan; Weiss, Daniel; Herrmann, Kai [in: Energies]
Understanding cycle-to-cycle variations (CCV) is of practical importance for the combustion of fossil and renewable fuels, as increasingly stringent emission regulations require reductions in the negative effects of such variations. The subject of this study is the flow around inlet valves, since oscillations of such inlet flows affect the flow structure in the cylinder and are thus one of the causes of CCV. To this end, a parametric analysis of the influences of the mass flow rate and valve lift of two parallel engine intake valves on the flow structures is performed. This follows on from an earlier similar study where the flow around a single intake valve was investigated. To analyse the flow behaviour and, in particular, the interactions of the flow leaving these two valves, an optical test rig for 2D particle image velocimetry (PIV) and a large eddy simulation (LES) are used. Proper orthogonal decomposition (POD), together with a quadruple decomposition and the Reynolds stress transport equations, are used to study the turbulence phenomena. The PIV and LES results are in good agreement with each other. The detailed LES analysis of the flow structures shows that, for small valve lifts, the flow separates along the whole perimeter of the intake valve, and for larger valve lifts, the flow escapes only to one side. This is, for combustion engines with the tumble concept, the stage at which the tumble movement develops. Moreover, the flow structures are strongly influenced by the valve lift, while they are unaffected by the variation in the mass flow. The turbulent kinetic energy in the flow field increases quadratically with a decreasing valve lift and increasing mass flow. The large, high-energetic flow structures are particularly dominant near the jet, and the small, low-energetic structures are homogeneously distributed within the flow field. The specific Reynolds stress transport equation shows the limitations of two-dimensionality and large timesteps in the PIV results and the limitations of the LES model.
01A - Beitrag in wissenschaftlicher Zeitschrift
Flow field investigation of a single engine valve using PIV, POD, and LES
(MDPI, 2023) Hoffmann, Jana; Mirsch, Niklas; Vera Tudela, Walter; Wüthrich, Dario; Rosenberg, Jorim; Günther, Marco; Pischinger, Stefan; Weiss, Daniel; Herrmann, Kai [in: Energies]
Due to stringent emission regulations, it is of practical significance to understand cycle-to-cycle variations in the combustion of fossil or renewable fuels to reach future emission regulations. The present study aims to conduct a parametric investigation to analyse the influence of the valve lift and different mass flows of an inlet valve of the test engine “Flex-OeCoS” on the flow structures. To gain a deeper understanding of the flow behaviour, an optical test bench for 2D Particle Image Velocimetry (PIV) and a Large Eddy Simulation (LES) are used. Turbulence phenomena are investigated using Proper Orthogonal Decomposition (POD) with a quadruple decomposition and the Reynolds stress transport equation. The results show good agreement between the PIV and LES. Moreover, the main flow structures are primarily affected by valve lift while being unaffected by mass flow variation. The turbulent kinetic energy within the flow field increases quadratically to the mass flow and to the decreasing valve lift, where large high-energetic flow structures are observed in the vicinity of the jet and small low-energetic structures are homogeneously distributed within the flow field. Furthermore, the convective flux, the turbulent diffusive flux, the rate of change, and the production of specific Reynolds stress are the dominant terms within the specific Reynolds stress transport equation.
01A - Beitrag in wissenschaftlicher Zeitschrift
Waste self-reporting for software development productivity improvement
(Springer, 2023) Sallin, Marc; Kropp, Martin; Anslow, Craig; Biddle, Robert; Stettina, Christoph J.; Garbajosa, Juan; Kruchten, Philippe [in: Agile processes in software engineering and extreme programming]
Little research has been done on enabling software development teams to self-report waste to assist in productivity improvement. This study created a waste categorization and survey for teams to identify and quantify wasteful activities. Developers from a Swiss company used the survey for three weeks. Participants found the survey helpful for identifying waste but there was little evidence that self-reported waste correlated with improved performance.
04B - Beitrag Konferenzschrift
Waveguide based passively demodulated photothermal interferometer for light absorption measurements of trace substances
(Optica Publishing Group, 2023) Visser, Bradley; Bilal, Jonas; Flöry, Nikolaus; Wipf, Manuela; Steigmeier, Peter; Rüggeberg, Tobias; Betschon, Felix; Weingartner, Ernest [in: Applied Optics]
01A - Beitrag in wissenschaftlicher Zeitschrift
Fused filament fabrication of bio-based polyether-block-amide polymers (PEBAX) and their related properties
(MDPI, 23.11.2022) Schär, Matthias; Zweifel, Lucian; Arslan, Delal; Grieder, Stefan; Maurer, Christoph; Brauner, Christian [in: Polymers]
This paper describes the application of poly(ether-block-amide) polymers, so-called Pebax, in fused filament fabrication (FFF). Pebax® is a thermoplastic elastomer (TPE), a copolymer based on rigid polyamide and soft polyether blocks. By variation of the blocks, unique properties such as soft or rigid behaviour are tailored without additional additives and plasticisers. Pebax®Rnew® polyamide blocks are bio-based and made from castor beans that allow the design of sustainable applications. In this study, two types of Pebax were selected, processing parameters were characterised, filaments were extruded and applied to FFF printing, and the final mechanical characteristics were determined. Both types were suitable for FFF processing with improved process stability due to less shear thinning and good mechanical performance. The connection strength between the grades was also described in the design context for complex parts with tailored soft or hard regions. Combining the two materials in one design is a promising concept, and the adhesion strength is close to the strength in the Z-direction of the flexible Pebax®Rnew®35R53 grade.
01A - Beitrag in wissenschaftlicher Zeitschrift
Measurement methods for RWB Emissions: what should be considered for a future standard?
(09.11.2022) Keller, Alejandro
06 - Präsentation
Einblick. Nach mehr als zwei Jahren Forschung gibt es Neuigkeiten zur Wirkung prismatischer Korrekturen beim Lesen
(Galledia, 10/2022) Joss, Joëlle; Jainta, Stephanie [in: Schweizer Optiker]
01B - Beitrag in Magazin oder Zeitung

Browse

Browsing Hochschule für Technik FHNW by publication date

Results per page

Sort options