Showing papers by "Technical University of Berlin published in 2023"

In Situ Coupling of Carbon Dots with Co‐ZIF Nanoarrays Enabling Highly Efficient Oxygen Evolution Electrocatalysis

Abstract: Metal-organic frameworks (MOFs) are regarded as one promising class of precatalysts for electrocatalytic oxygen evolution reaction (OER), yet most of them suffer from poor conductivity and lack of coordinatively unsaturated metal sites, which hinders the fast electrochemical reconstruction and thus a poor OER activity. To address this issue, a unique heterocomposite has been constructed by in situ inserting carbon dots (CDs) into cobalt-based zeolitic imidazolate framework (Co-ZIF) nanosheet arrays (Co-ZIF/CDs/CC) in the presence of carbon cloth (CC) via one-pot coprecipitation for alkaline OER. Benefiting from the synergism between CDs and Co-ZIF subunits such as superior conductivity, strong charge interaction as well as abundant metal sites exposure, the Co-ZIF/CDs/CC exhibits an enhanced promotion effect for OER and contributes to the deep phase transformation from CDs-coupled Co-ZIF to CDs-coupled active CoOOH. As expected, the achieved Co-ZIF/CDs/CC only requires an overpotential of 226 mV to deliver 10 mA cm−2 in 1.0 M KOH, which is lower than that of Co-ZIF/CC and superior to most previously reported CC-supported MOF precatalysts. Moreover, it can also maintain a large current density of 100 mA cm−2 for 24 h with negligible activity decay.

Observation of Multi‐Directional Energy Transfer in a Hybrid Plasmonic–Excitonic Nanostructure

Abstract: Hybrid plasmonic devices involve a nanostructured metal supporting localized surface plasmons to amplify light–matter interaction, and a non-plasmonic material to functionalize charge excitations. Application-relevant epitaxial heterostructures, however, give rise to ballistic ultrafast dynamics that challenge the conventional semiclassical understanding of unidirectional nanometal-to-substrate energy transfer. Epitaxial Au nanoislands are studied on WSe2 with time- and angle-resolved photoemission spectroscopy and femtosecond electron diffraction: this combination of techniques resolves material, energy, and momentum of charge-carriers and phonons excited in the heterostructure. A strong non-linear plasmon–exciton interaction that transfers the energy of sub-bandgap photons very efficiently to the semiconductor is observed, leaving the metal cold until non-radiative exciton recombination heats the nanoparticles on hundreds of femtoseconds timescales. The results resolve a multi-directional energy exchange on timescales shorter than the electronic thermalization of the nanometal. Electron–phonon coupling and diffusive charge-transfer determine the subsequent energy flow. This complex dynamics opens perspectives for optoelectronic and photocatalytic applications, while providing a constraining experimental testbed for state-of-the-art modelling.

Report-Dependent Utility and Strategy-Proofness

Abstract: Despite the truthful dominant strategy, participants in strategy-proof mechanisms submit manipulated preferences. In our model, participants dislike rejections and enjoy the confirmation from getting what they declare desirable. Formally, the payoff from a match decreases in its position in the submitted ranking such that a strategic trade-off between preference intensity and match probability arises. This trade-off can trigger the commonly observed self-selection strategies. We show that misrepresentations can persist for arbitrarily small report-dependent components. However, honesty is guaranteed to be optimal if and only if there is no conflict between the quality and feasibility of a match. We substantiate the theory with already existing evidence and provide novel testable predictions. This paper was accepted by Yan Chen, behavioral economics and decision analysis. Funding: This work was supported by UniCredit and Universities Foundation [Modigliani Research Grant 2020/2021] and Deutsche Forschungsgemeinschaft [Grant 280092119]. Supplemental Material: The online appendix is available at https://doi.org/10.1287/mnsc.2022.4504 .

Emerging Materials for Interfacial Solar‐Driven Water Purification

Abstract: Solar-driven water purification is considered as an effective and sustainable technology for water treatment using green solar energy. One major goal for practical applications is to improve the solar evaporation performance by the design of novel photothermal materials, with optimized heat localization and water transport pathways to achieve reduced energy consumption for water vaporization. Recently, some emerging materials like polymers, metal-organic frameworks (MOFs), covalent organic frameworks (COFs) and also single molecules were employed to construct novel solar evaporation systems. In this minireview, we present an overview of the recent efforts on materials development for water purification systems. The state-of-the-art applications of these emerging materials for solar-driven water treatment, including desalination, wastewater purification, sterilization and energy production, are also summarized.

William Siemens: An Engineer and Industrialist in Germany and England

Abstract: Abstract This article’s author researches physical, cultural, and technological spaces in England and Germany in the nineteenth century. He examines the cases of the Siemens companies in both countries and William Siemens (1823–1883), who was first educated in Germany and later moved to England, where he became a well-known and distinguished professional engineer. His themes are the industrial and technological state of England and Germany, the business strategies of the Siemens companies, the education and training of English and German engineers, and William Siemens’ opinions on technological development. In all these points, the spaces of England and Germany shaped technological development.

Digital Supply Chain Twins for Sustainable Planning of a Logistics System

Abstract: Abstract Digital Supply Chain Twins (DSCT) are gaining more and more attention both in science and in practices. They are considered to be one of the most disruptive technologies in logistics and supply chain management. In the literature, there are a variety of DSCT benefits in the case of planning and control a logistics system. Some of these potentials could also be highly suitable for the use case of sustainable and resource-efficient logistics, which, however, have been insufficiently explored in research so far. This paper will investigate to what extent the DSCT can be used to enable sustainable network planning and which potentials the DSCT implies for the predictive planning within logistics systems. Building on a literature review and interviews with industry experts a case study was conducted at a business partner in the automotive industry.

Meta-modeling with data-driven methods in hydrology

Abstract: Process-based models are the standard tools today when trying to understand how physical systems work. There are situations however, when system understanding is not a primary focus and it is worth substituting existing process-based models with computationally more efficient meta-models (or emulators), i.e. proxies designed for specific applications. In our research we have explored potential data-driven meta-modeling approaches for applications in hydrology, designed to solve specific research questions.In order to find a suitable meta-modeling approach, we have experimented with a set of different data-driven methods. We have employed a multi-fidelity modeling approach, where we gradually increased the complexity of our models. In total five different approaches were investigated: linear model with ordinary least squares regression, linear model with two different Bayesian methods (Hamiltonian Monte Carlo and transdimensional Monte Carlo) and two machine learning approaches (dense artificial neural network and long short-term memory (LSTM) neural network).For method development the project case study of the Groß Glienicker Lake was used. This is a glacial lake near Berlin, with a strong negative trend in water levels in the last decades. Supported by the observation model from the Central European Refined analysis, we had a daily, high resolution meteorological dataset (precipitation and actual evapotranspiration) and lake level observations for 16 years.All of the used models are designed similarly: they predict lake level changes one day ahead using precipitation and evapotranspiration data from the previous 70 days. This interval was selected after an extensive parameter test with the linear model. By predicting the change in stored water, we linearize the problem, and by using a longer time interval we allow the methods to automatically compensate for any lag or memory effects inside the catchment. The different methods are evaluated by comparing the fits between the observed and the reconstructed lake levels.As expected, increasing the model and inversion complexity improves the quality of the reconstruction. Especially the use of nonlinear models was advantageous, the artificial neural network outperformed every other method. However, in the used example these improvements were relatively small – meaning that in practice the simplest linear method was advantageous due to its computational efficiency and robustness, and ease of use and interpretation.In this presentation we discuss the challenges of data preparation and optimal model design (especially the memory of the hydrological system), while finding the hyperparameters of the specific methods themselves was relatively straight forward. Our results suggest that problem linearization should be a preferred first step in any meta-modeling application, as it helps the training of nonlinear models as well. We also discuss data requirements, because we found that the size of our dataset was too small for the most complex LSTM method, which yielded unstable results and learned spurious background trends.

Reply on RC3

Abstract: Abstract. The Volyn biota, fossilized organisms with a minimum age of 1.5 Ga, were found in cavities in granitic pegmatites from the Korosten pluton, NW Ukrainian shield. Fossilization was due to influx of hydrothermal fluorine-rich waters, which silicified the outermost part of the organisms, thus preserving the 3D morphology. Details of the morphology (investigated by scanning electron microscopy) show that the majority of the specimens is filamentous, of a large variety with diameters ranging from ~10 µm to ~200 µm, thin filaments with typical branching, thick filaments with ball-shaped outgrowths and dented surface. Filaments can be straight or conical, curvilinear or strongly curved, up to mm in length, some with a central channel. Some filaments show indications for segmentation, are grown as sessile organisms onto substrate; others show both intact ends, indicating growth in soft medium or floating in water. Objects with flaky morphology and agglutinating filaments are interpreted as fossil biofilms. Other objects are hollow and show a large variety of forms; spherical objects are scarce. Infrared spectroscopy indicates the presence of chitosan in one filament, electron microprobe analysis of nm-sized inclusions in filaments identified the presence of Bi(Te,S) minerals, and both observations are compatible with the interpretation of filaments as fungi-like organisms. Stable C- and N-isotope data of bulk samples are in the range of -31 to -47 ‰ δ¹³C/¹²C, and of +3 to +10 ‰ δ¹⁵N/¹⁴N, indicating possible methanogenic bacteria as part of the subsurface micro-ecosystem. The Volyn biota show that at 1.5 Ga fungi-like organisms lived in the continental deep biosphere, where complex forms of life existed, well above the microscopic level.

A 0.4 pJ/bit NRZ Voltage Mode VCSEL Driver for up to 224 Gbit/s SWDM Links

Abstract: We present the first true voltage-mode VCSEL driver achieving 60 Gbit/s at peak efficiency of 0.36pJ/bit with BER < 1e-12 improving the state-of-the-art by a factor of 2. Transmission experiments showcase error-free 56 Gbit/s transmission up to 100 m fiber. Advanced demonstration enables even 224 Gbit/s when using SWDM at a total efficiency of 0.4 pJ/bit.

Discrimination of the Enantiotopic Faces of Structurally Unbiased Carbenium Ions Employing a Cyclohexadiene‐Based Chiral Hydride Source

Abstract: An enantioselective reduction of simple carbenium ions with cyclohexadienes containing a hydridic C–H bond at an asymmetrically substituted carbon atom is disclosed. The net reaction is a transfer hydrogenation of alkenes (styrenes) only employing chiral cyclohexadienes as dihydrogen surrogates. The trityl cation is used to initiate a Brønsted acid-promoted process, in which a delicate intermolecular capture of a carbenium-ion intermediate by the aforementioned chiral hydride source is enantioselectivity determining. Exclusively non-covalent interactions are rendering one of the transition states energetically more favored, giving the reduction products in good enantiomeric ratios. The computed reaction mechanism supports the present findings as well as previous results obtained from studies on other transfer-hydrogenation methods involving the cyclohexadiene platform.

The fate of nitrification and urease inhibitors in simulated bank filtration&amp;#160;

Abstract: Nitrification and urease inhibitors (NUI) are used in conjunction with nitrogen (N) fertilizers on agricultural soils to improve the efficiency of N fertilizers and reduce the emission of greenhouse gases. After application, NUI might transfer to aquatic environments through leaching or surface runoff. Nowadays, NUI such as 1,2,4-triazole, 3,4-dimethylpyrazole (3,4-DMPP) and dicyandiamide (DCD) are frequently found in surface waters with concentrations in the magnitude of &#181;g/L. The fate of NUI in bank filtration (BF) is currently poorly known. BF is a sustainable water treatment system providing high quality water by efficiently removing numerous organic micropollutants from the source water. Herein, sorption and degradation of NUI in simulated BF under near-natural conditions was investigated. Besides, the effect of NUI on the microbial biomass of slowly growing microorganisms and the role of microbial biomass on NUI removal was investigated. Duplicate sand columns (length 1.7 m), fed with surface water were spiked with a pulse consisting of four nitrification (1,2,4-triazole, DCD, 3,4-DMPP and 3-methylpyrazole) and two urease inhibitors (n-butyl-thiophosphoric acid triamide and n-(2-nitrophenyl) phosphoric triamide). The average spiking concentration of each NUI was 5 &#181;g/L. The flow velocity was adjusted to 0.2 m/d. Breakthrough curves of tracer (sodium chloride) and the NUI appeared at same time; therefore, sorption may be ruled out. Additionally, experimental and modeled breakthrough curves of NUI suggested no retardation for any of the inhibitors. Therefore, biodegradation was identified as the main elimination pathway for all substances and was highest in zones of high microbial biomass. N-butyl-thiophosphoric acid triamide was completely removed within a hydraulic retention time (HRT) of 24 hours and proved to be a highly degradable substance. Nitrification inhibitors showed 50% mass recovery (except for 3,4-DMPP) after an HRT of 4 days. A slight effect of NUI on microbial biomass was observed. This study highlights that hydraulic retention time and microbial biomass are key indicators for the degradation of NUI.

Reply on Daniel Wasner

Abstract: Abstract. Ultrasonication combined with density fractionation (USD) is a method widely used to quantify soil organic matter pools. A selective fractionation of free particulate organic matter (fPOM) is crucial to avoid co-extraction of retained fPOM along with occluded particulate organic matter (oPOM). In the present work, artificial fPOM was extracted from two mineral matrices, sandy and loamy, after applying different approaches for merging sample and dense medium. It could be shown that pouring the dense solution to the mineral matrices leads to low recovery, whereas trickling the sample into the solution, rotating after fill-up or applying a minimal and defined amount of ultrasound to swirl up the sample causes nearly full recovery of the artificial fPOM. Applied to natural soils, the results confirmed the low extraction rate of the fill-up approach. Moreover, it was possible to show that the rotational approach results in only a slightly increased extraction rate, whereas the ultrasound approach leads to a release of oPOM into the fPOM fraction due to disruption of soil macro-aggregates. The trickle approach appears to be the most appropriate way among the tested methods to achieve complete and selective extraction of fPOM from natural soil samples.

Exploitation of GNSS tropospheric gradients for severe weather Monitoring And Prediction (EGMAP): Project status and Initial results

Abstract: Data assimilation (DA) is a tool that is capable of combining observations and numerical weather models (NWMs) in an optimal manner. Current DA systems used by operational forecasting centres are constantly evolving and getting better than before. High-quality observations are very important for the accurate representation of variables in a weather model. In this study, we are incorporating Global Navigation Satellite System (GNSS) tropospheric gradients and Zenith Total Delays (ZTDs) into the Weather Research and Forecasting (WRF) model. WRF model has its operator already developed for the ZTDs and in this research, we are developing a new operator for the assimilation of tropospheric gradients. The assimilation of ZTDs, which are closely related to Integrated Water Vapor (IWV) above the GNSS station, has a positive impact on weather forecasts. On the other hand, tropospheric gradients are not yet assimilated by the weather agencies. Our research is based on a project titled &#8220;Exploitation of GNSS tropospheric gradients for severe weather Monitoring And Prediction&#8221; (EGMAP) focusing on the impact of GNSS tropospheric gradients and how it can be effectively used for operational forecasting of severe weather. EGMAP is funded by the German Research Foundation (DFG).The observation operator currently in use for tropospheric gradients is based on a linear combination of ray-traced tropospheric delays (Zus et al., 2022). This observation operator is challenging to be implemented into an NWM DA system. We will thus rely on a more simple and fast observation operator which is based on the closed-form expression depending on the north&#8211;south and east&#8211;west horizontal gradients of atmospheric refractivity (Davis et al., 1993).Initial testing of the operator is done on a 0.1 x 0.1-degree mesh configured over Central Europe in the WRF model with 50 vertical levels up to 50 hPa. The model configuration will be later upgraded to a convective-scale resolution after initial testing of the tropospheric gradient operator. Model forcing observations are derived from the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) data at 0.25-degree resolution. Conventional observations are obtained from the European Centre for Medium-Range Weather Forecasts (ECMWF) and are the base dataset for the assimilation studies. The conventional datasets used for assimilation are restricted to surface stations (SYNOP observations) and radiosondes. Additionally, observations from roughly 100 GNSS stations are assimilated at each DA cycle. Three experiments are conducted: 1) Control run with only conventional data; 2) ZTD assimilation on top of the control run, and; 3) ZTD and tropospheric gradient assimilation on top of the control run. Initial DA tests are being performed with an automated rapid update cycle DA framework with 6 hourly intervals based on a deterministic three-Dimensional Variational (3DVar) DA system for the testing of ZTDs and tropospheric gradients. The DA system will be later upgraded to a probabilistic one based on the Hybrid 3DVar-Ensemble Transform Kalman Filter (-ETKF, Thundathil et al., 2021) and 4DEnVar. The EGMAP project status and initial results from the impact of GNSS-ZTDs and tropospheric gradients will be presented.

Forschungsstrategie und methodische Vorgehensweise

Abstract: Angesichts der Fragestellung dieser Untersuchung ist der konkrete Raumbezug für das Forschungsdesign konstitutiv. Für die empirische Analyse der Mechanismen und Wirkungsweisen des institutionellen Antiziganismus ist eine rekonstruktive Einzelfallstudie am Beispiel einer deutschen Großstadt angezeigt. Die untersuchte Großstadt wurde insbesondere aus zwei forschungsstrategischen Gründen ausgewählt: einerseits konnten wir dort einen seit 2012 sich intensivierenden kommunalen Problematisierungsdiskurs bezüglich der EU-Binnenmigration aus Rumänien und Bulgarien diagnostizieren und andererseits etablierten sich im zeitlichen Verlauf diesbezüglich neue institutionelle Handlungsroutinen in den gesellschaftlichen Funktionssystemen a) Unterbringung und Wohnen, b) Arbeitsmarkt und wohlfahrtsstaatliche Dienstleistungen, c) Bildung und Schule sowie d) im Gesundheitswesen.

Exploration of the lunar deep interior through global deformation modeling.

Abstract: The Moon is the most well-known extraterrestrial planetary body thanks to observations from ground-based, space-borne instruments and lunar surface missions. Data from Lunar Laser Ranging (LLR), magnetic, gravity, surface observations and seismic Apollo ground stations help us to quantify the deformation undergone by the Moon due to body tides. These observations provide one of the most significant constraints that can be employed to unravel the deep interior. The Moon deforms in response to tidal forcing exerted by, to first order, the Earth, the Sun and, to a lesser extent, by other planetary bodies. We use the degree-2 tidal Love number as a tool for studying the inner structure of our satellite. Based on measurements of the tidal Love numbers k2 and h2 and quality factors from the GRAIL mission, LLR and Laser Altimetry on board the LRO spacecraft, we perform a random walk Monte Carlo samplings for combinations of thicknesses and viscosities for models of Moon with and without inner core. By comparing predicted and observed parameters of the lunar tidal deformations, we infer constraints on the outer core viscosity, for a Moon with a thin outer core and a thick inner core, and a Moon with a thicker outer core but a denser and thinner inner core. In addition, by deducing the temperature and assuming the chemical composition of the low-viscosity zone, we obtain stringent constraints on its radius, viscosity and density.&#160;

Reply on RC2

Abstract: Long-term measurements of permafrost temperatures do not provide a complete picture of the Arctic subsurface thermal regime. Regions with warmer permafrost often show little to no long-term change in ground temperature due to the uptake and release of latent heat during freezing and thawing. Thus, regions where the least warming is observed may also be the most vulnerable to permafrost degradation. Since direct measurements of ice and liquid water contents in the permafrost layer are not widely available, thermal modeling of the subsurface plays a crucial role in understanding how permafrost responds to changes in the local energy balance. In this work, we first analyze trends in observed air and permafrost temperatures at four sites within the continuous permafrost zone, where we find substantial variation in the apparent relationship between long-term changes in permafrost temperatures (0.02 K yr−1 to 0.16 K yr−1) and air temperature (0.09 K yr−1 to 0.11 K yr−1). We then apply recently developed Bayesian inversion methods to link observed changes in borehole temperatures to unobserved changes in latent heat and thaw depth using a transient model of heat conduction with phase change. Our results suggest that the degree to which recent warming trends correlate with permafrost thaw and variations in latent heat is heavily dependent on both local soil properties as well as historical climatology. At the warmest site, a nine meter borehole near Ny-Ålesund, Svalbard, modeled annual maximum thaw depth increases by an average of (12 ± 1) cm K−1 rise in mean annual ground temperature. In stark contrast, modeled thaw rates for a borehole on Samoylov Island in the Lena River Delta (northeastern Siberia) appear far less sensitive to temperature change, with an almost negligible increase of (1 ± 1) cm K−1. Although our study is limited to just four sites, the results urge caution in the interpretation and comparison of warming trends in Arctic boreholes, indicating substantial uncertainty in their implications for the current and future thermal state of permafrost.

On Point Predictions and Reference Dependence in Behavior-Based Pricing Experiments

Abstract: It has been shown that the comparative static results of two-period behavior-based pricing models hold in laboratory experiments, while point predictions do not. This study aims to check whether these findings replicate and to evaluate why observed prices deviate from point predictions. We report observed prices in conformity with point predictions through: (1.) a uniform pricing benchmark, (2.) a replication of a behavior-based pricing experiment, and (3.) a follow-up experiment in which we consider the second period disjointed from the first period. By disjoining the two periods, we show that reference dependence toward first-period prices shifts the second-period pricing behavior of participants upwards. In a post hoc analysis, we show that considering consumers' myopic instead of strategic explains a downward shift in first-period prices and rationalizes prior experimental findings. Volatile price levels affect price-based welfare measures – such as seller profits and total customer costs. We show that transport costs are a robust welfare measure that alleviates the impact of distorted prices. Ultimately, our findings are relevant for the design and assessment of multi-period pricing experiments.

Multi-GNSS Tomography: Case Study of the July 2021 Flood in Germany

Abstract: Abstract Due to climate change, intensive storms and severe precipitation will continue to happen, causing destructive flooding. In July 2021, a series of storms with prolonged rain episodes took place in Europe. Several countries were affected by severe floods following that rainfall, causing many deaths and material damage. Thus, a good understanding and forecasting of such events are of uttermost importance. This study highlights the interest of multi-GNSS tomography for the 3D modelling of the neutral atmosphere refractivity. The tropospheric parameters have been retrieved for the July 2021 flood in Germany from two tomographic solutions with different constraining options using either GPS-only or multi-GNSS estimates. Our investigations show that the stand-alone solution (especially the multi-GNSS) is producing more patterns of refractivity, and is temporally more stable. We compare the tomographic results with external observations such as radiosondes and GNSS radio-occultations from Metop-A & -B satellites. The results show that tomography is producing wetter conditions than the reference. However, we can see the precursor information of the initiation of deep convection in the ground-based GNSS technique.

Fundamentals

Abstract: This chapter describes the foundations and related work of speech quality, dialogue systems, and dialogue simulation. The fundamentals in speech quality focus on the two technical impairments delay and packet loss, as well as the assessment of conversational quality, which includes the parametric conversation analysis method. Also, an introduction to instrumental speech quality prediction, with a focus on the E-model, will be given. The fundamentals in spoken dialogue systems will outline the use cases of dialogue simulation and the architectural details needed for the implementation of a conversation simulation.

Conversational Quality Predictions

Abstract: In this chapter, the simulated conversations are used to predict the conversational quality based on the parameters of the conversation, as well as based on the fullband E-model, with a focus on transmission delay and bursty packet loss. In order to test the suitability of simulated conversations for the prediction, a parameter-based model for the prediction of the impact of delay on a conversation is created and evaluated based on empirical data. Then, the E-model is extended toward interactivity parameters used to predict the effects of transmission delay, as well as toward burstiness parameters to predict the impact of bursty packet loss on a conversation. The adaptions to the E-model are evaluated on empirical data as well as on predictions from the POLQA model. Finally, the created parameter-based model and the extended E-model are utilized to predict the conversational quality based on the simulated conversations, and the results are compared to the empirical data and prediction of the extended E-model based on general transmission parameters.