Hochschule für Technik und Umwelt FHNW

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A comprehensive dynamic model of the diamond wire sawing process
(WIP, 2017) Treyer, Daniel; Gaulocher, Sebastian; Niederberger, Stefan; Rafael, Helge; Ams, Alfons; Smets, A.; Helm, P.; Taylor, N.
04B - Beitrag Konferenzschrift
A dual-wavelength photothermal aerosol absorption monitor. Design, calibration and performance
(Copernicus, 2022) Drinovec, Luka; Jagodič, Uroš; Pirker, Luka; Škarabot, Miha; Kurtjak, Mario; Vidović, Kristijan; Ferrero, Luca; Visser, Bradley; Röhrbein, Jannis; Weingartner, Ernest; Kalbermatter, Daniel M.; Vasilatou, Konstantina; Bühlmann, Tobias; Pascale, Celine; Müller, Thomas; Wiedensohler, Alfred; Močnik, Griša
There exists a lack of aerosol absorption measurement techniques with low uncertainties and without artefacts. We have developed the two-wavelength Photothermal Aerosol Absorption Monitor (PTAAM-2λ), which measures the aerosol absorption coefficient at 532 and 1064 nm. Here we describe its design, calibration and mode of operation and evaluate its applicability, limits and uncertainties. The 532 nm channel was calibrated with ∼ 1 µmol mol−1 NO2, whereas the 1064 nm channel was calibrated using measured size distribution spectra of nigrosin particles and a Mie calculation. Since the aerosolized nigrosin used for calibration was dry, we determined the imaginary part of the refractive index of nigrosin from the absorbance measurements on solid thin film samples. The obtained refractive index differed considerably from the one determined using aqueous nigrosin solution. PTAAM-2λ has no scattering artefact and features very low uncertainties: 4 % and 6 % for the absorption coefficient at 532 and 1064 nm, respectively, and 9 % for the absorption Ångström exponent. The artefact-free nature of the measurement method allowed us to investigate the artefacts of filter photometers. Both the Aethalometer AE33 and CLAP suffer from cross sensitivity to scattering – this scattering artefact is most pronounced for particles smaller than 70 nm. We observed a strong dependence of the filter multiple scattering parameter on the particle size in the 100–500 nm range. The results from the winter ambient campaign in Ljubljana showed similar multiple scattering parameter values for ambient aerosols and laboratory experiments. The spectral dependence of this parameter resulted in AE33 reporting the absorption Ångström exponent for different soot samples with values biased 0.23–0.35 higher than the PTAAM-2λ measurement. Photothermal interferometry is a promising method for reference aerosol absorption measurements.
01A - Beitrag in wissenschaftlicher Zeitschrift
A European aerosol phenomenology - 6. Scattering properties of atmospheric aerosol particles from 28 ACTRIS sites
(Copernicus, 2018) Pandolfi, Marco; Alados-Arboledas, Lucas; Alastuey, Andrés; Andrade, Marcos; Angelov, Christo; Artiñano, Begoña; Backman, John; Baltensperger, Urs; Bonasoni, Paolo; Bukowiecki, Nicolas; Collaud Coen, Martine; Conil, Sébastien; Coz, Esther; Crenn, Vincent; Dudoitis, Vadimas; Ealo, Marina; Eleftheriadis, Kostas; Favez, Olivier; Fetfatzis, Prodromos; Fiebig, Markus; Flentje, Harald; Ginot, Patrick; Gysel, Martin; Henzing, Bas; Hoffer, Andras; Holubova Smejkalova, Adela; Kalapov, Ivo; Kalivitis, Nikos; Kouvarakis, Giorgos; Kristensson, Adam; Kulmala, Markku; Lihavainen, Heikki; Lunder, Chris; Luoma, Krista; Lyamani, Hassan; Marinoni, Angela; Mihalopoulos, Nikolaos; Moerman, Marcel; Nicolas, José; O'Dowd, Colin D.; Petäjä, Tuukka; Petit, Jean-Eudes; Pichon, Jean Marc; Prokopciuk, Nina; Putaud, Jean-Philippe; Rodríguez, Sergio; Sciare, Jean; Sellegri, Karine; Swietlicki, Erik; Titos, Gloria; Tuch, Thomas; Tunved, Peter; Ulevicius, Vidmantas; Vaishya, Aditya; Vana, Milan; Virkkula, Aki; Vratolis, Stergios; Weingartner, Ernest; Wiedensohler, Alfred; Laj, Paolo
This paper presents the light-scattering properties of atmospheric aerosol particles measured over the past decade at 28 ACTRIS observatories, which are located mainly in Europe. The data include particle light scattering (σsp) and hemispheric backscattering (σbsp) coefficients, scattering Ångström exponent (SAE), backscatter fraction (BF) and asymmetry parameter (g). An increasing gradient of σsp is observed when moving from remote environments (arctic/mountain) to regional and to urban environments. At a regional level in Europe, σsp also increases when moving from Nordic and Baltic countries and from western Europe to central/eastern Europe, whereas no clear spatial gradient is observed for other station environments. The SAE does not show a clear gradient as a function of the placement of the station. However, a west-to-east-increasing gradient is observed for both regional and mountain placements, suggesting a lower fraction of fine-mode particle in western/south-western Europe compared to central and eastern Europe, where the fine-mode particles dominate the scattering. The g does not show any clear gradient by station placement or geographical location reflecting the complex relationship of this parameter with the physical properties of the aerosol particles. Both the station placement and the geographical location are important factors affecting the intra-annual variability. At mountain sites, higher σsp and SAE values are measured in the summer due to the enhanced boundary layer influence and/or new particle-formation episodes. Conversely, the lower horizontal and vertical dispersion during winter leads to higher σsp values at all low-altitude sites in central and eastern Europe compared to summer. These sites also show SAE maxima in the summer (with corresponding g minima). At all sites, both SAE and g show a strong variation with aerosol particle loading. The lowest values of g are always observed together with low σsp values, indicating a larger contribution from particles in the smaller accumulation mode. During periods of high σsp values, the variation of g is less pronounced, whereas the SAE increases or decreases, suggesting changes mostly in the coarse aerosol particle mode rather than in the fine mode. Statistically significant decreasing trends of σsp are observed at 5 out of the 13 stations included in the trend analyses. The total reductions of σsp are consistent with those reported for PM2.5 and PM10 mass concentrations over similar periods across Europe.
01A - Beitrag in wissenschaftlicher Zeitschrift
A global study of hygroscopicity-driven light-scattering enhancement in the context of other in situ aerosol optical properties
(Copernicus, 2021) Titos, Gloria; Burgos, María A.; Zieger, Paul; Alados-Arboledas, Lucas; Baltensperger, Urs; Jefferson, Anne; Sherman, James; Weingartner, Ernest; Henzing, Bas; Luoma, Krista; O'Dowd, Colin; Wiedensohler, Alfred; Andrews, Elisabeth
The scattering and backscattering enhancement factors (f(RH) and fb(RH)) describe how aerosol particle light scattering and backscattering, respectively, change with relative humidity (RH). They are important parameters in estimating direct aerosol radiative forcing (DARF). In this study we use the dataset presented in Burgos et al. (2019) that compiles f(RH) and fb(RH) measurements at three wavelengths (i.e., 450, 550 and 700 nm) performed with tandem nephelometer systems at multiple sites around the world. We present an overview of f(RH) and fb(RH) based on both long-term and campaign observations from 23 sites representing a range of aerosol types. The scattering enhancement shows a strong variability from site to site, with no clear pattern with respect to the total scattering coefficient. In general, higher f(RH) is observed at Arctic and marine sites, while lower values are found at urban and desert sites, although a consistent pattern as a function of site type is not observed. The backscattering enhancement fb(RH) is consistently lower than f(RH) at all sites, with the difference between f(RH) and fb(RH) increasing for aerosol with higher f(RH). This is consistent with Mie theory, which predicts higher enhancement of the light scattering in the forward than in the backward direction as the particle takes up water. Our results show that the scattering enhancement is higher for PM1 than PM10 at most sites, which is also supported by theory due to the change in scattering efficiency with the size parameter that relates particle size and the wavelength of incident light. At marine-influenced sites this difference is enhanced when coarse particles (likely sea salt) predominate. For most sites, f(RH) is observed to increase with increasing wavelength, except at sites with a known dust influence where the spectral dependence of f(RH) is found to be low or even exhibit the opposite pattern. The impact of RH on aerosol properties used to calculate radiative forcing (e.g., single-scattering albedo, ω0, and backscattered fraction, b) is evaluated. The single-scattering albedo generally increases with RH, while b decreases. The net effect of aerosol hygroscopicity on radiative forcing efficiency (RFE) is an increase in the absolute forcing effect (negative sign) by a factor of up to 4 at RH = 90 % compared to dry conditions (RH < 40 %). Because of the scarcity of scattering enhancement measurements, an attempt was made to use other more commonly available aerosol parameters (i.e., ω0 and scattering Ångström exponent, αsp) to parameterize f(RH). The majority of sites (75 %) showed a consistent trend with ω0 (higher f(RH = 85 %) for higher ω0), while no clear pattern was observed between f(RH = 85 %) and αsp. This suggests that aerosol ω0 is more promising than αsp as a surrogate for the scattering enhancement factor, although neither parameter is ideal. Nonetheless, the qualitative relationship observed between ω0 and f(RH) could serve as a constraint on global model simulations.
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
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
A prototype system for the hydrothermal oxidation of feces
(Elsevier, 14.11.2022) Affolter, Joël; Brunner, Thomas; Hagger, Nicola; Vogel, Frédéric
To ensure access to safe sanitation facilities in rural communities, cheap off-grid technologies need to be developed to substitute pit latrines and open defecation. In this study, we present a prototype system based on hydrothermal oxidation, which, under optimal conditions, converts a fecal sludge simulant almost completely to CO2 and water, leaving behind only a carbon-poor aqueous phase with the minerals. The prototype has been designed to process the feces from two households. This technology does not only enable a fast and complete conversion, but is potentially also very energy efficient, as the feed does not require any pre-treatment or drying. The system was found to effectively remove 97–99% of the total organic carbon within a reaction time of 600 s under an external energy demand of roughly 4 kWh per kilogram of wet feces by using the oxygen in air as an oxidant. A total of ten experiments with varying injection pressure, total solids content of the feed, and residence time in the reactor were performed to find experimental settings with high conversion. Only when the residence time was decreased from 600 to 300 s did the conversion fall significantly below 97%. To reach a target value of 99.9% TOC conversion, the reactor temperature and/or the residence time must be increased further. To achieve a system applicable in regions with no connection to the energy grid, the thermal loss of the reactor insulation needs to be lowered further to achieve an overall thermally self-sustaining operation.
01A - Beitrag in wissenschaftlicher Zeitschrift
A single-beam photothermal interferometer for in situ measurements of aerosol light absorption
(Copernicus, 2020) Visser, Bradley; Röhrbein, Jannis; Steigmeier, Peter; Drinovec, Luka; Močnik, Griša; Weingartner, Ernest
We have developed a novel single-beam photothermal interferometer and present here its application for the measurement of aerosol light absorption. The use of only a single laser beam allows for a compact optical set-up and significantly easier alignment compared to standard dual-beam photothermal interferometers, making it ideal for field measurements. Due to a unique configuration of the reference interferometer arm, light absorption by aerosols can be determined directly – even in the presence of light-absorbing gases. The instrument can be calibrated directly with light-absorbing gases, such as NO2, and can be used to calibrate other light absorption instruments. The detection limits (1σ) for absorption for 10 and 60 s averaging times were determined to be 14.6 and 7.4 Mm−1, respectively, which for a mass absorption cross section of 10 m2 g−1 leads to equivalent black carbon concentration detection limits of 1460 and 740 ng m−3, respectively. The detection limit could be reduced further by improvements to the isolation of the instrument and the signal detection and processing schemes employed.
01A - Beitrag in wissenschaftlicher Zeitschrift
A synthesis of cloud condensation nuclei counter (CCNC) measurements within the EUCAARI network
(Copernicus, 2015) Paramonov, Mikhail; Kerminen, Veli-Matti; Gysel, Martin; Aalto, Pasi Pekka; Andreae, Meinrat O.; Asmi, Eija; Baltensperger, Urs; Bougiatioti, Aikaterini; Brus, David; Frank, Göran; Good, Nicholas; Gunthe, Sachin S.; Hao, Liqing; Irwin, Martin; Jaatinen, Antti; Jurányi, Zsófia; King, S. M.; Kortelainen, Aki; Kristensson, Adam; Lihavainen, Heikki; Kulmala, Markku; Lohmann, Ulrike; Martin, Scot T.; McFiggans, Gordon; Mihalopoulos, Nikolaos; Nenes, Athanasios; O'Dowd, Colin D.; Ovadnevaite, Jurgita; Petäjä, Tuukka; Pöschl, Ulrich; Roberts, Greg; Rose, Diana; Svenningsson, Birgitta; Swietlicki, Erik; Weingartner, Ernest; Whitehead, James; Wiedensohler, Alfred; Wittbom, Cerina; Sierau, Berko
Cloud condensation nuclei counter (CCNC) measurements performed at 14 locations around the world within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) framework have been analysed and discussed with respect to the cloud condensation nuclei (CCN) activation and hygroscopic properties of the atmospheric aerosol. The annual mean ratio of activated cloud condensation nuclei (NCCN) to the total number concentration of particles (NCN), known as the activated fraction A, shows a similar functional dependence on supersaturation S at many locations – exceptions to this being certain marine locations, a free troposphere site and background sites in south-west Germany and northern Finland. The use of total number concentration of particles above 50 and 100 nm diameter when calculating the activated fractions (A50 and A100, respectively) renders a much more stable dependence of A on S; A50 and A100 also reveal the effect of the size distribution on CCN activation. With respect to chemical composition, it was found that the hygroscopicity of aerosol particles as a function of size differs among locations. The hygroscopicity parameter κ decreased with an increasing size at a continental site in south-west Germany and fluctuated without any particular size dependence across the observed size range in the remote tropical North Atlantic and rural central Hungary. At all other locations κ increased with size. In fact, in Hyytiälä, Vavihill, Jungfraujoch and Pallas the difference in hygroscopicity between Aitken and accumulation mode aerosol was statistically significant at the 5 % significance level. In a boreal environment the assumption of a size-independent κ can lead to a potentially substantial overestimation of NCCN at S levels above 0.6 %. The same is true for other locations where κ was found to increase with size. While detailed information about aerosol hygroscopicity can significantly improve the prediction of NCCN, total aerosol number concentration and aerosol size distribution remain more important parameters. The seasonal and diurnal patterns of CCN activation and hygroscopic properties vary among three long-term locations, highlighting the spatial and temporal variability of potential aerosol–cloud interactions in various environments.
01A - Beitrag in wissenschaftlicher Zeitschrift
Aerosol emission in a road tunnel
(Elsevier, 02/1997) Weingartner, Ernest; Keller, Christian; Stahel, Werner; Burtscher, Heinz; Baltensperger, Urs
Continuous measurements of aerosol emissions were performed within the scope of emission measurements in the Gubrist tunnel, a 3250 m long freeway tunnel near Zürich, Switzerland, from 20 September to 26 September 1993. The particles in the respirable size range (d < 3 μm) were found to be mainly tail pipe emissions with very small amount of tire wear and road dust. The calculated PM3 emission factor for diesel engines was about 310 mg/km, where the main part (63%) of the diesel vehicles were heavy-duty vehicles. Thirty-one percent of the PM3 emissions from diesel vehicles were black carbon and 0.86% particle bound PAR Due to the high fraction emitted by diesel engines the contribution of gasoline engines could not be evaluated by the statistical model. During their residence time in the tunnel the particles undergo significant changes, resulting in a more compact structure. It is concluded that this is mainly due to adsorption of volatile material from the gas phase to the particle surface.
01A - Beitrag in wissenschaftlicher Zeitschrift
Aktive Schallauslöschung für Bürostühle
(VDI Fachmedien, 2016) Treyer, Daniel; Gaulocher, Sebastian; Germann, Silvano
01B - Beitrag in Magazin oder Zeitung
Ambient and laboratory observations of organic ammonium salts in PM₁
(Royal Society of Chemistry, 2017) Schlag, Patrick; Rubach, Florian; Mentel, Thomas F.; Reimer, David Thomas; Canonaco, Francesco; Henzing, Bas; Moerman, M.; Otjes, R.; Prévôt, André S.H.; Rohrer, Franz; Rosati, B.; Tillmann, Ralf; Weingartner, Ernest; Kiendler-Scharr, Astrid
Ambient measurements of PM₁aerosol chemical composition at Cabauw, the Netherlands, implicate higher ammonium concentrations than explained by the formation of inorganic ammonium salts. This additional particulate ammonium is called excess ammonium (e_NH4). Height profiles over the Cabauw Experimental Site for Atmospheric Research (CESAR) tower, of combined ground based and airborne aerosol mass spectrometric (AMS) measurements on a Zeppelin airship show higher concentrations ofe_NH4at higher altitudes compared to the ground. Through flights across the Netherlands, the Zeppelin based measurements furthermore substantiatee_NH4as a regional phenomenon in the planetary boundary layer. The excess ammonium correlates with mass spectral signatures of (di-)carboxylic acids, making a heterogeneous acid–base reaction the likely process of NH₃uptake. We show that this excess ammonium was neutralized by the organic fraction forming particulate organic ammonium salts. We discuss the significance of such organic ammonium salts for atmospheric aerosols and suggest that NH₃emission control will have benefits for particulate matter control beyond the reduction of inorganic ammonium salts.
01A - Beitrag in wissenschaftlicher Zeitschrift
Analysis of long‐term aerosol size distribution data from Jungfraujoch with emphasis on free tropospheric conditions, cloud influence, and air mass transport
(Wiley, 2015) Herrmann, Erik; Weingartner, Ernest; Henne, Stephan; Vuilleumier, Laurent; Bukowiecki, Nicolas; Steinbacher, Martin; Conen, Franz; Collaud Coen, Martine; Hammer, Emanuel; Jurányi, Zsófia; Baltensperger, Urs; Gysel, Martin
Six years of aerosol size distribution measurements between 20 and 600 nm diameters and total aerosol concentration above 10 nm from March 2008 to February 2014 at the high‐alpine site Jungfraujoch are presented. The size distribution was found to be typically bimodal with mode diameters and widths relatively stable throughout the year and the observation period. New particle formation was observed on 14.5% of all days without a seasonal preference. Particles typically grew only into the Aitken mode and did not reach cloud condensation nucleus (CCN) sizes on the time scale of several days. Growth of preexisting particles in the Aitken mode, on average, contributed very few CCN. We concluded that the dominant fraction of CCN at Jungfraujoch originated in the boundary layer. A number of approaches were used to distinguish free tropospheric (FT) conditions and episodes with planetary boundary layer (PBL) influence. In the absence of PBL injections, the concentration of particles larger than 90 nm (N90, roughly corresponding to the CCN concentration) reached a value ~40 cm−3 while PBL influence caused N90 concentrations of several hundred or even 1000 cm−3. Comparing three criteria for free tropospheric conditions, we found FT prevalence for 39% of the time with over 60% during winter and below 20% during summer. It is noteworthy that a simple criterion based on standard trace gas measurements appeared to outperform alternative approaches.
01A - Beitrag in wissenschaftlicher Zeitschrift
Application of multi-parametric quadratic programming to simulation of deflected wires in a wire saw
(Wiley, 2017) Treyer, Daniel; Gaulocher, Sebastian; Niederberger, Stefan; Rafael, Helge; Ams, Alfons; Könke, Carsten; Trunk, Carsten
04B - Beitrag Konferenzschrift
Co-curing behaviour of thermoset composites with a thermoplastic boundary layer for welding purposes
(SAGE, 17.03.2020) Brauner, Christian; Nakouzi, Sawsane; Zweifel, Lucian; Tresch, Jens
The primary objective of this study is to determine the interphase behaviour of a thermoset epoxy resin that is commercially used for carbon fibre–reinforced composite materials in aerospace structures and a suitable thermoplastic material that can be used as a boundary layer. The thermoplastic boundary layer will be used for welding purposes to join structural components with a fraction of the effort compared to conventional gluing processes. In this study, the interphase formation of an epoxy resin with several thermoplastic materials, namely, polyetheretherketone, polyvinylidenfluoride, polyphenylensulfide and polyetherimide (PEI), is studied via hot-stage microscope experiments. Based on this study, PEI was selected, and a detailed study was performed to determine the dependency of dissolution, diffusion and phase separation mechanisms under various isothermal conditions. Additionally, the welding behaviour was investigated by a resistance welding rig whereby the process parameters were statistically varied to optimize the lap shear strength. The results of this study will enable a statement about the interphase development, the morphology and the mechanical properties which is a key element of fully understanding the process.
01A - Beitrag in wissenschaftlicher Zeitschrift
Comparing black carbon and aerosol absorption measuring instruments – a new system using lab-generated soot coated with controlled amounts of secondary organic matter
(Copernicus, 2022) Kalbermatter, Daniel M.; Močnik, Griša; Drinovec, Luka; Visser, Bradley; Röhrbein, Jannis; Oscity, Matthias; Weingartner, Ernest; Hyvärinen, Antti-Pekka; Vasilatou, Konstantina
We report on an inter-comparison of black-carbon- and aerosol-absorption-measuring instruments with laboratory-generated soot particles coated with controlled amounts of secondary organic matter (SOM). The aerosol generation setup consisted of a miniCAST 5201 Type BC burner for the generation of soot particles and a new automated oxidation flow reactor based on the micro smog chamber (MSC) for the generation of SOM from the ozonolysis of α-pinene. A series of test aerosols was generated with elemental to total carbon (EC / TC) mass fraction ranging from about 90 % down to 10 % and single-scattering albedo (SSA at 637 nm) from almost 0 to about 0.7. A dual-spot Aethalometer AE33, a photoacoustic extinctiometer (PAX, 870 nm), a multi-angle absorption photometer (MAAP), a prototype photoacoustic instrument, and two prototype photo-thermal interferometers (PTAAM-2λ and MSPTI) were exposed to the test aerosols in parallel. Significant deviations in the response of the instruments were observed depending on the amount of secondary organic coating. We believe that the setup and methodology described in this study can easily be standardised and provide a straightforward and reproducible procedure for the inter-comparison and characterisation of both filter-based and in situ black-carbon-measuring (BC-measuring) instruments based on realistic test aerosols.
01A - Beitrag in wissenschaftlicher Zeitschrift
Condition-based maintenance. Model vs. statistics a performance comparison
(Curran, 2016) Engeler, Marc; Treyer, Daniel; Zogg, David; Kunz, Andreas; Wegener, Konrad; Westkämper, Engelbert; Bauernhansl, Thomas
04B - Beitrag Konferenzschrift
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
Diamond wire wafering. A model-based evaluation of different control strategies
(Wip, 2018) Treyer, Daniel; Gaulocher, Sebastian; Niederberger, Stefan; Rafael, Helge; Frech, Gregor; Ams, Alfons; Verlinden, Pierre; Kenny, Robert; Helm, Peter
04B - Beitrag Konferenzschrift
Dual-wavelength light-scattering technique for selective detection of volcanic ash particles in the presence of water droplets
(Copernicus, 2015) Jurányi, Zsófia; Burtscher, Heinz; Loepfe, Markus; Nenkov, Maxim; Weingartner, Ernest
A new method is presented in this paper which analyses the scattered light of individual aerosol particles simultaneously at two different wavelengths in order to retrieve information on the particle type. We show that dust-like particles, such as volcanic ash, can be unambiguously discriminated from water droplets on a single-particle level. As a future application of this method, the detection of volcanic ash particles should be possible in a humid atmosphere in the presence of cloud droplets. The characteristic behaviour of pure water's refractive index can be used to separate water droplets and dust-like particles which are commonly found in the micrometre size range in the ambient air. The low real part of the water's refractive index around 2700–2800 nm results in low scattered light intensities compared to e.g. the visible wavelength range, and this feature can be used for the desired particle identification. The two-wavelength measurement set-up was theoretically and experimentally tested and studied. Theoretical calculations were done using Mie theory. Comparing the ratio of the scattered light at the two wavelengths (visible-to-IR (infrared), R value) for water droplets and different dust types (basalt, andesite, African mineral dust, sand, volcanic ash, pumice) showed at least 9-times-higher values (on average 70 times) for water droplets than for the dust types at any diameter within the particle size range of 2–20 μm. The envisaged measurement set-up was built up into a laboratory prototype and was tested with different types of aerosols. We generated aerosols from the following powders, simulating dust-like particles: cement dust, ISO 12103-1 A1 Ultrafine Test Dust and ash from the 2012 eruption of the Etna volcano. Our measurements verified the theoretical considerations; the median experimental R value is 8–21 times higher for water than for the "dust" particles.
01A - Beitrag in wissenschaftlicher Zeitschrift
Experimental and numerical development on multi-material joining technology for sandwich-structured composite materials
(MDPI, 12.10.2021) Zweifel, Lucian; Zhilyaev, Igor; Brauner, Christian; Rheme, Martin; Eckhard, Gregor; Bersier, Valentin; Glavaški, Slobodan; Pfeiffer, Ricardo
Creating connection points for sandwich-structured composites without losing technical performance is key to realising optimal lightweight structures. The patented LiteWWeight® technology presents cost-effective connections on sandwich panels in a fraction of a few seconds without predrilling. Ultrasonic equipment is used to insert a thermoplastic fastener into the substrate material and partially melt it into the porous internal structure. This creates a highly interlocked connection (connection strength is above 500 N) suitable for semi-structural applications. This study focused on the simulation and experimental validation of this process, mainly on the interaction between the pin and the substrate material during the joining process. The dynamic thermo-mechanical model showed reasonable agreement with experimental methods such as process data, high-speed camera monitoring or computed tomography and allowed the prediction of the connection quality by evaluation of the degree of interlock. The connection strength prediction by the developed model was validated within several various process setups, resulting in a prediction accuracy between 94–99% depending on the setup.
01A - Beitrag in wissenschaftlicher Zeitschrift