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Highly Efficient Homodyne Cryogenic Readout Link Based on a Silicon-Organic Hybrid (SOH) Phase Modulator
No full textEffects of Mn Doping on Surface Chemistry, Phase Stability, and Physical Properties of NiO Synthesized via Green Methods
No full textThis study investigates the effect of manganese (Mn) doping (1–5 wt. %) on the phase transition of nickel hydroxide (Ni(OH)) to nickel oxide nanoparticles (NiO NPs) synthesized via a green route. Phase transition, structural, optical, and magnetic properties of Mn-doped NiO are thoroughly investigated. Thermogravimetric analysis (TGA) reveals the influence of Mn on the thermal decomposition and the stability of Ni(OH) and the organic compounds from olive leaf extract under inert calcination conditions. X-ray photoelectron spectroscopy (XPS) provides insights into surface chemistry modifications before and after calcination, as well as in the presence of Mn. X-ray diffraction (XRD) confirms Mn incorporation and lattice distortion within the NiO structure. HRTEM and BET analyses show that 2 wt. % Mn is a critical concentration, yielding the smallest spherical particle size (6 nm) and the highest surface area. The calculated work function from ultraviolet photoelectron spectroscopy (UPS) reveals a decrease from 6.0 eV (0 wt. % Mn) to 5.4 eV (5 wt. % Mn). Analysis of the valence band maximum (VBM) region further indicates a bandgap widening with Mn incorporation. Raman spectra reveal the appearance of the two magnon (2M) vibrational mode, suggesting modified magnetic behavior. Vibrating sample magnetometry (VSM) indicates a ferromagnetic response, with the appearance of a Néel temperature at 5 wt. % Mn, indicating an antiferromagnetic to paramagnetic transition. This study offers key insights into the design of stable, high-performance materials for photovoltaic and magnetic applications
Robustness of critical soil moisture to curve-fitting methods and its variability with soil depth, soil texture, and climatic conditions: insights from lysimeter data in Germany
No full textActual evapotranspiration (ET) is a vital terrestrial ecosystem process that links water, energy, and carbon cycles. ET can be limited by either energy or water availability. The transition between water- and energy-limited regimes is related to soil moisture and is often characterized as a threshold, denoted as critical soil moisture threshold (θ). However, the determination of θ is subject to uncertainties due to the different methods used to evaluate the relationship between ET and soil moisture (SM), such as SM depths, definitions of ET and curve fitting functions. Typically, surface SM is used to identify θ as it is easily accessible and assumed to represent root zone SM status. Weighable lysimeter technology provides a unique opportunity to assess the role of root zone SM on the transition between water and energy limited ET. It is widely regarded as the gold standard for measuring in-situ ET, and at the same time allows for in-situ SM measurements at different depths. In this study, we estimated θ using in situ SM measurements at 10 cm depth and root zone SM by vertically integrating in situ SM (0–60 cm) observations. In addition, we applied three different definitions of relative evapotranspiration (evaporative fraction, the ratio of ET to grass reference evapotranspiration and the ratio of actual ET to calculated potential (vapotranspiration) as well as two different fitting curves to investigate the sensitivities of θ. We found robust θ estimates across different definitions and fitting curve methods, but the estimates were significantly higher for root zone than for surface θ. Our results also highlight the high correlation (0.83) between root zone and surface θ. However, the relation between both values is not unique since it depends on the actual moisture profile and plant root system and, herewith, on the soil type and previous weather conditions. We further observed that both surface and root zone θ decreased with increasing sand fraction. Under changing climatic conditions but with identical soil and ecosystem types, both surface and root zone θ decreased with increasing aridity. Additionally, we found that using the midpoint between field capacity and wilting point provides a reliable range of root zone θ for a given soil texture
Neural Network-Based Estimation of Muon Content from Data Recorded by the SD-1500 of the Pierre Auger Observatory
No full textUltra-high-energy cosmic rays (UHECRs) offer insights into the physics beyond the energies of human-made accelerators. However, to fully understand processes such as their acceleration, precise knowledge of their mass composition is crucial. Since the direct detection of UHECRs is infeasible, determining the mass of the primary particles is challenging. One method of accessing this information is to estimate the number of muons produced in extensive air showers (EASs). The direct measurement of high-energy muons in an EAS can be achieved by using arrays of buried detectors, such as the Underground Muon Detector (UMD) at the Pierre Auger Observatory. However, the instrumentation area of the UMD is limited in size. One of the central components of the Pierre Auger Observatory is the Surface Detector (SD), which consists of multiple triangular grids of hybrid detector stations. These stations record the time signals of the secondary particles that are produced in EASs that reach the ground. In this contribution, we present a neural network (NN) that utilizes SD-1500 data, the main surface detector array of the Pierre Auger Observatory, to predict the muon content of EASs. This NN is calibrated indirectly to the UMD measurements using a calibrated NN designed for the SD-750, the second-largest surface detector array located near the UMD
Probing binary black hole merger populations in AGN disks through future IceCube-Gen2 and Einstein Telescope observations
No full textThe detection of astrophysical neutrinos and gravitational waves (GWs) has ushered in a new era of multi-messenger astroparticle physics. While coincident detections of GW and neutrinos alongside electromagnetic signals have already been achieved in separate instances, no common source of GW and neutrinos has yet been identified. To address the implications of non-detection, this work investigates the prospects for identifying binary black hole mergers embedded in AGN disks as common GW-neutrino sources with next-generation facilities, e.g., the Einstein Telescope and IceCube-Gen2. For sources located in the Northern Hemisphere, the detection significance is quantified for both individual mergers and their populations, to be seen by the Einstein Telescope. It is found that, even with improved sensitivity of next-generation detectors, catalogue searches have limited potential. In contrast, stacking offers a viable path to uncover a population of common GW-neutrino sources in the future
Unravelling Charge Storage and Degradation in Cathodes for Rechargeable Aluminium Batteries: A Synergistic Study of CoSe Cathodes and MXenes-Based Components
No full textDiese Dissertation präsentiert eine umfassende Untersuchung des elektrochemischen Verhaltens und der Degradationsmechanismen von Kobaltselenid-(CoSe)-Kathoden in wiederaufladbaren Aluminiumbatterien. Es wurde ein multifunktionaler Ansatz angewendet, der elektrochemische Tests, ex situ-Analysen sowie fortgeschrittene in situ- und operando -Charakterisierungstechniken auf Synchrotronbasis kombiniert.
Die Studie schließt kritische Wissenslücken in der Literatur und zeigt eine anfängliche Amorphisierung von CoSe sowie eine Phasenumwandlung von hexagonalem CoSe zu kubischem CoSe2, begleitet von der Auflösung von Co(AlCl4)2, das migriert und sich auf der Aluminium-Anode abscheidet. Die Ladungsspeicherung erfolgt über die reversible Redoxreaktion von Se²⁻ zu Se⁻, während Co²⁺ elektrochemisch inaktiv bleibt. Die Auflösung und Abscheidung von Co(AlCl4)2 tragen durch den Verlust aktiven Materials und die Kontamination der Anode zum Kapazitätsverlust bei, wie durch ex situ-SEM-EDX- und ICP-OES-Analysen bestätigt wurde.
Zur Untersuchung der in CoSe identifizierten Degradationspfade wird im zweiten Teil dieser Arbeit die multifunktionale Rolle von Ti3C2TX als passive Komponente untersucht. Die geschichtete Struktur der Ti3C2TX-MXene wurde zunächst ausgewählt, um Separatoren zu modifizieren, da sie das Potenzial besitzt, den Transport gelöster Spezies zu unterdrücken. Aufgrund ihrer überzeugenden physikochemischen Eigenschaften, wie hoher Leitfähigkeit, einstellbarer Oberflächenchemie und mechanischer Stabilität, wurde Ti3C2TX weiter hinsichtlich seiner Rolle bei der Verbesserung der Leistung von Kathoden für RABs untersucht. Ti3C2TX wurde als Stromableiter und Separatoradditiv evaluiert, mit dem Ziel, die Elektrodenintegrität und Leitfähigkeit zu verbessern und den Verlust aktiver Materialien zu verringern. Obwohl Ti3C2TX -basierte Separatoren eine leichte Reduktion des Kobalt-Shuttlings zeigen, reicht dies nicht aus, um die Migration vollständig zu unterdrücken, was die Bedeutung einer zukünftigen Optimierung des Separator-Designs hervorhebt. Dieser integrierte Ansatz unterstreicht die Bedeutung des Verständnisses sowohl der Mechanismen aktiver Materialien als auch der Wechselwirkungen passiver Komponenten, um die Leistungsfähigkeit und Stabilität chalcogenidbasierter Elektroden für RABs zu verbessern. Die Ergebnisse etablieren ein mechanistisches Rahmenkonzept, das die Grundlage für andere Übergangsmetall-Chalkogenid-Chemien legt und zukünftige Strategien zur Unterdrückung von Degradationsprozessen sowie zur Entwicklung langlebiger, leistungsstarker wiederaufladbarer Aluminiumbatterien aufzeigt
Synthesis of Gasoline and Kerosene by Heterogeneously Catalyzed (Co‐)Oligomerization of Ethylene, Propylene, and Iso‐Butylene
No full textThe heterogeneously catalyzed co-oligomerization of ethylene, propylene, and iso-butylene was studied focusing on the production of gasoline and kerosene. Silica-alumina catalysts were employed with and without nickel loading. Initially, the homo-oligomerization of iso-butylene was studied employing a series of catalysts and varying reaction conditions. Due to the high reactivity of iso-butylene, conversion was almost quantitative and selectivities to kerosene reached 96% while selectivities to gasoline reached 83%. Subsequently, co-oligomerization of iso-butylene with ethylene and propylene was investigated. Employing nickel-loaded silica-alumina catalysts, all olefin species can be converted, despite the very different reactivity. Selectivities to kerosene and gasoline were up to 92% and 83%, respectively. It is shown that iso-butylene can be easily separated from such olefin mixtures by oligomerization, due to its much higher reactivity compared to propylene and ethylene. A long-term run lasting for 196 h showed continuous deactivation of the catalyst regarding the conversion of ethylene and propylene, whereas conversion of iso-butylene remained close to 100%. As a result, conversion of iso-butylene dominates and molecular branching increases, as indicated by the isoindex. It is shown that the catalyst can be easily reactivated by heating and catalytic performance can be fully restored
In-situ spectral calibration from plasma measurements of the W7-X Thomson scattering diagnostic
No full textOptimal Piecewise Linear Approximations for Sigmoid, Tanh, Probability Density and Cumulative Distribution Functions: Tabular Form and R Package pwlapprox2d
No full textWe present information in tabular form about optimal piecewise linear (PWL) approximations
of the sigmoid and tanh activation functions as used in neural networks, as well as the probabil-
ity density and cumulative distribution functions of the Normal and log-Normal distributions.
The presented approximations minimise the maximum absolute difference between the PWL
function and the continuous function being modelled; we also provide information on opti-
mal over- and underestimators. We provide information on the optimal breakpoint locations
for different numbers of breakpoints in a series of tables, as well as the accuracy provided by
these approximations. This allows practitioners to utilise the PWL approximations whenever
needed; for example, to enable the use of mixed-integer linear programming techniques to
solve problems where these functions may appear, or to approximate integrals. The provided
optimal breakpoint locations lead to an improvement over a uniform breakpoint location
of the maximum absolute difference of up to 95% and an average of 84% among the six
functions