Consistent Set Of Parameters Research Articles

High-Resolution spectroscopy and analysis of the fundamental modes of [formula omitted]Si[formula omitted]. Accurate experimental determination of the Si[formula omitted]F bond length

Silicon tetrafluoride (SiF4) is a trace component of volcanic gases and is gaining industrial importance. However, a better knowledge of spectroscopic parameters is needed for this molecule in order to derive accurate concentrations. Following a previous reinvestigation of the ν3 and ν4 fundamentals (Richard et al. 2021), we have undertaken an extensive high-resolution study of its infrared absorption bands. We present here an update of this study. It features the recording of new far-infrared spectra, taking advantage of synchrotron radiation, and a global fit giving a consistent parameter set for the ground and fundamental states of 28SiF4, now including the v1=1 and v2=1 states, by adding to the global analysis the newly measured ν2, ν1−ν4, and ν4−ν2 bands near 264, 412, and 125 cm−1, respectively. Nearly 20000 assigned lines pertaining to seven distinct rovibrational bands were fitted with an excellent accuracy (global standard deviation of 0.296). This allows us to obtain an accurate experimental value for the Si−F bond length, re(SiF4)=1.5516985(30) Å. Some new band intensity estimates allow us to update our SiF4 calculated spectroscopic database.

Isomerization and Redox Tuning: Reorganizing the Maya Blue Puzzle from Synthetic, Spectral, and Electrochemical Issues

A new approach to describe the composition of Maya blue (MB), an ancient organic–inorganic hybrid material, is presented. It is based on the analysis of attenuated total reflection-Fourier transform infrared (ATR-FTIR), Raman spectroscopy, UV–visible (vis) spectroscopic, and electrochemical data for indigo and dehydroindigo plus palygorskite hybrids, including a novel methodology using electrocatalytic effects on the oxygen reduction reaction. As a result, it is concluded that MB results from the tautomerization of indigo-to-indigo hemienol and the subsequent oxidation of these isomeric forms to dehydroindigo, all associated with the palygorskite clay framework, at temperatures above 100 °C. This model is also consistent with 13C NMR data on indigo plus sepiolite hybrids. A consistent set of thermochemical parameters is obtained from ATR-FTIR, solid-state electrochemistry, and UV–vis diffuse reflectance spectra for the successive isomerization and redox tuning processes experienced by palygorskite-associated indigo.

DATA: Diafiltration Apparatus for high-Throughput Analysis

Improved characterization techniques, which address knowledge gaps related to the interfacial processes that govern solute–solute selectivity and the performance of membranes in complex multi-component feed streams, are necessary to advance membrane processes. In this study, guided by the tools of data science, a diafiltration apparatus is developed to inform material and process design by rapidly characterizing membrane performance over a broad range of feed solution compositions. The apparatus doses a fixed-concentration diafiltrate solution into a stirred cell to achieve a predetermined change in the retentate concentration. Here, using an 80 mM potassium chloride (KCl) diafiltrate solution, it was shown that membrane performance, within a 5 mM to 80 mM KCl phase space, could be probed five times more quickly with one diafiltration experiment (8 h) than with an experimental campaign using traditional filtration processes (47 h). Additionally, the synergy between data analytics and instrumentation led to the incorporation of an inline conductivity probe that monitored the real-time retentate concentration. This additional information provided key insights to distinguish between the mechanisms that govern membrane separations (e.g., discriminating between adsorption or rejection based separations) and allowed for the membrane transport coefficients to be determined accurately. Ultimately, incorporating the appropriate governing phenomena identified a single set of self consistent transport parameters for commercial NF90 membranes.

Coupled hydro-mechanical analysis of compacted bentonite behaviour during hydration

This study analyses the response of compacted bentonites upon hydration based on a coupled hydro-mechanical elasto-plastic framework. As an alternative to multi-porosity interpretation, the framework was selected based on the experimental evidence of adsorbed water behaviour in bentonites and the volumetric response at saturated states, apparently independent of its initial state. Based on these premises, a water retention model was formulated using an explicit distinction between adsorbed water and free water, enabling the postulation of the water properties and behaviour depending on its state. In order to effectively account for the transition between unsaturated to saturated state, that can occur in a wide range of suctions, the stress–strain constitutive equations are written in terms of an effective stress and degree of saturation framework. The mathematical formulation was implemented in a finite element code and used to simulate and interpret the behaviour of MX-80 bentonite compacted in different forms during hydration for several stress paths, including loading and unloading cycles after saturation. A good agreement of the model with experimental results was obtained using a consistent set of parameters describing the saturated state behaviour. The typical non-linear swelling pressure development was interpreted through the two-way coupling between the water retention behaviour and elasto-plastic compressibility. The possible high suctions at saturated states explain the swelling potential after full hydration. Overall, this study offers new perspectives on the role of hydro-mechanical interactions in bentonite behaviour upon hydration.

Thermospheric Parameters during Ionospheric G-Conditions

For the first time thermospheric parameters (neutral composition, exospheric temperature and vertical plasma drift related to thermospheric winds) have been inferred for ionospheric G-conditions observed with Millstone Hill ISR on 11–13 September 2005; 13 June 2005, and 15 July 2012. The earlier developed method to extract a consistent set of thermospheric parameters from ionospheric observations has been revised to solve the problem in question. In particular CHAMP/STAR and GOCE neutral gas density observations were included into the retrieval process. It was found that G-condition days were distinguished by enhanced exospheric temperature and decreased by ~2 times of the column atomic oxygen abundance in a comparison to quiet reference days, the molecular nitrogen column abundance being practically unchanged. The inferred upward plasma drift corresponds to strong ~90 m/s equatorward thermospheric wind presumably related to strong auroral heating on G-condition days.

Revisiting interpretation of relative density from shallow depth CPTs in sand

The relative density is an important state parameter in the determination of engineering properties of marine sands. Existing industry-acknowledged cone penetration test (CPT) correlations to relative density have been developed almost exclusively from the results of calibration chamber testing performed at stress levels higher than 50 kPa. A few studies suggest correlations for low stress levels as well, however, mainly for unaged normally consolidated soils. Existing formulations are often found to be challenged in the application for dense to very dense aged overconsolidated marine sands. This paper investigates the conditions and response of overconsolidated medium dense to very dense sand (as typically found in the North Sea) at shallow depths (less than 50 kPa) for a penetrating cone. It provides recommendations for a consistent set of parameters linking CPT parameters to the stress conditions, expressed by the apparent overconsolidation ratio and coefficient of earth pressure at rest, and the relative density. The recommendations are based on a comprehensive field-testing campaign at a sand site in Cuxhaven, Germany, supported by a suite of laboratory testing and numerical analyses.

Challenges in the Application of Manganese Oxide Powders as OER Electrocatalysts: Synthesis, Characterization, Activity and Stability of Nine Different MnxOy Compounds

AbstractManganese oxides are seen as potential electrocatalysts for the alkaline oxygen evolution reaction (OER). To find the most suitable OER catalyst among the large number of known manganese oxide compounds, several comparative studies of selected MnxOy materials in water oxidation catalysis were reported in recent years with, in some cases, conflicting results. In this study, nine different manganese oxide powders differing in structure and/or composition were synthesized, characterized and compared regarding their OER activity and stability using a consistent set of experimental parameters. It turned out that the activity generally depends strongly on the manganese oxide compound. α‐MnO2 manganese oxides of the hollandite‐type were found to be more active than those with a lower oxidation state or other crystal structures. The most active catalyst cryptomelane, α‐(K)MnO2, reached a current density of 10 mA/cm2 at 1.77±0.02 V in LSV measurements. At a potential of 1.8 V, the current density was approximately 15 mA cm−2. In contrast, the samples with the lowest activity exhibited values less than 1 mA cm−2 at the same potential. The stability experiments revealed a fast decrease in activity of all samples within the first minutes of measurement and an almost complete activity loss after 60 min. Conductivity differences are discussed as a likely reason for the observed differences in performance.

27‐3: Optimizing Charge Transport and Reducing Excitonic Loss Channels in Fluorescent Doped TADF OLEDs

A combined experimental and simulation study on a set of 4 OLEDs with 2 systematically varied guest dopants in the emission layer is presented. A numerical electro‐optical model is employed, demonstrating one consistent parameter set that describes both steady‐state and ac characteristics of all devices. The model accounts for charge transport and trapping, polar layers, and excitonic loss processes inducing an efficiency rolloff that can be correlated with the shape of the emission zone and the guest dopant concentrations. Furthermore, starting from the resulting parameter set, we show routes for optimized devices with a reduced roll‐off.

Physico-chemical parameter measurement and model response evaluation for a pseudo-two-dimensional model of a commercial lithium-ion battery

To effectively evaluate battery performance by means of electrochemical modelling, a consistent set of parameters is essential. The aim of this work is to provide a complete physico-chemical methodology to measure all the necessary parameters for a pseudo-two-dimensional (P2D) electrochemical model. Component composition, thermodynamic, kinetic and transport properties, parameters related to the porous structures, internal battery configuration and full-cell electrode balancing are presented for a commercial lithium-ion battery. Then, the measured parameters are entered into the P2D model, and battery responses are evaluated against full-cell experimental curves (galvanostatic charge-discharge at different current rates, EIS responses and pulses) to correlate numerical-experimental results.

Spin dynamics and Griffiths singularity in the random quantum Ising magnet PrTiNbO6

In crystalline magnets, interaction randomness is usually thought as a negative factor preventing interesting quantum phenomena to occur. However, intriguing interplay between randomness and quantumness can also leads to unique phenomena in the strongly correlated materials. Among others, the random transverse-field Ising spin chain (RTIC) hosts a renowned quantum Griffiths phase. Although the RTIC model has been regarded as a toy model for long, here we materialize this model with the compound PrTiNbO6, which has a disordered ground state with pronounced quantum fluctuations and continuous spin excitations. The observed anomalous spin dynamics of PrTiNbO6 can be accounted by the RTIC model with a consistent set of parameters determined from fitting the thermodynamic data, and it is ascribed to the quantum Griffiths rare regions in the system. Our results provide a concrete example of quantum Griffiths magnet, and offer an ideal experimental platform for investigating the dynamical properties of random many-body system.

OceanSODA-ETHZ: a global gridded data set of the surface ocean carbonate system for seasonal to decadal studies of ocean acidification

Abstract. Ocean acidification has profoundly altered the ocean's carbonate chemistry since preindustrial times, with potentially serious consequences for marine life. Yet, no long-term, global observation-based data set exists that allows us to study changes in ocean acidification for all carbonate system parameters over the last few decades. Here, we fill this gap and present a methodologically consistent global data set of all relevant surface ocean parameters, i.e., dissolved inorganic carbon (DIC), total alkalinity (TA), partial pressure of CO2 (pCO2), pH, and the saturation state with respect to mineral CaCO3 (Ω) at a monthly resolution over the period 1985 through 2018 at a spatial resolution of 1∘×1∘. This data set, named OceanSODA-ETHZ, was created by extrapolating in time and space the surface ocean observations of pCO2 (from the Surface Ocean CO2 Atlas, SOCAT) and total alkalinity (TA; from the Global Ocean Data Analysis Project, GLODAP) using the newly developed Geospatial Random Cluster Ensemble Regression (GRaCER) method (code available at https://doi.org/10.5281/zenodo.4455354, Gregor, 2021). This method is based on a two-step (cluster-regression) approach but extends it by considering an ensemble of such cluster regressions, leading to improved robustness. Surface ocean DIC, pH, and Ω were then computed from the globally mapped pCO2 and TA using the thermodynamic equations of the carbonate system. For the open ocean, the cluster-regression method estimates pCO2 and TA with global near-zero biases and root mean squared errors of 12 µatm and 13 µmol kg−1, respectively. Taking into account also the measurement and representation errors, the total uncertainty increases to 14 µatm and 21 µmol kg−1, respectively. We assess the fidelity of the computed parameters by comparing them to direct observations from GLODAP, finding surface ocean pH and DIC global biases of near zero, as well as root mean squared errors of 0.023 and 16 µmol kg−1, respectively. These uncertainties are very comparable to those expected by propagating the total uncertainty from pCO2 and TA through the thermodynamic computations, indicating a robust and conservative assessment of the uncertainties. We illustrate the potential of this new data set by analyzing the climatological mean seasonal cycles of the different parameters of the surface ocean carbonate system, highlighting their commonalities and differences. Further, this data set provides a novel constraint on the global- and basin-scale trends in ocean acidification for all parameters. Concretely, we find for the period 1990 through 2018 global mean trends of 8.6 ± 0.1 µmol kg−1 per decade for DIC, −0.016 ± 0.000 per decade for pH, 16.5 ± 0.1 µatm per decade for pCO2, and −0.07 ± 0.00 per decade for Ω. The OceanSODA-ETHZ data can be downloaded from https://doi.org/10.25921/m5wx-ja34 (Gregor and Gruber, 2020).

Microplane fatigue model MS1 for plain concrete under compression with damage evolution driven by cumulative inelastic shear strain

Mathematical modeling of fatigue behavior of concrete under compressive loading presents a challenging topic that attracts an increasing interest of the scientific community. The present paper proposes a new formulation of the microplane model referred to as MS1 aiming to capture the fundamental inelastic mechanisms that can reflect the tri-axial stress redistribution within a material zone upon cyclic loading at subcritical load levels. The key idea of the proposed approach is to link the fatigue damage evolution to the cumulative inelastic shear strain. In this way the accumulation of fatigue damage under compressive loading owing to internal shear/sliding between aggregates at subcritical load levels can be reflected. The present model is developed within the context of the microplane theory using a homogenization scheme based on the principle of energy equivalence with a direct tensorial representation of the effective elastic stiffness. The paper presents elementary studies of the model behavior accompanied with the evaluation of its capability to capture the response of concrete fatigue under compressive loading. A calibration and validation procedure of the model response is provided based on an accompanying experimental program including normal- and high-strength concretes subjected to several loading scenarios. The model shows the ability to reproduce the concrete behavior under monotonic, cyclic and fatigue loading with consistent set of material parameters.

Validation of an optical potential for incident and emitted low-energy alpha -particles in the Asim 60 mass range

A consistent set of statistical-model input parameters, validated by analysis of various independent data, makes possible the assessment of an alpha -particle optical model potential [Phys. Rev. C 90, 044612 (2014)] also for nucleon-induced alpha -emission within the A sim 60 mass-number range. The advantage of recent data for low-lying states feeding is taken as well. Consideration of additional reaction channels leading to increase of the alpha -emission beyond the statistical predictions has concerned the pickup direct interaction and Giant Quadrupole Resonance similar features.

Robust Vegetation Parameterization for Green Roofs in the EPA Stormwater Management Model (SWMM)

In increasingly expanding cities, roofs are still largely unused areas to counteract the negative impacts of urbanization on the water balance and to reduce flooding. To estimate the effect of green roofs as a sustainable low impact development (LID) technique on the building scale, different approaches to predict the runoff are carried out. In hydrological modelling, representing vegetation feedback on evapotranspiration (ET) is still considered challenging. In this research article, the focus is on improving the representation of the coupled soil–vegetation system of green roofs. Relevant data to calibrate and validate model representations were obtained from an existing field campaign comprising several green roof test plots with different characteristics. A coupled model, utilizing both the Penman–Monteith equation to estimate ET and the software EPA stormwater management model (SWMM) to calculate the runoff, was set up. Through the application of an automatic calibration procedure, we demonstrate that this coupled modelling approach (Kling–Gupta efficiency KGE = 0.88) outperforms the standard ET representation in EPA SWMM (KGE = −0.35), whilst providing a consistent and robust parameter set across all green roof configurations. Moreover, through a global sensitivity analysis, the impact of changes in model parameters was quantified in order to aid modelers in simplifying their parameterization of EPA SWMM. Finally, an improved model using the Penman–Monteith equation and various recommendations are presented.

Methodology of selecting a molecular substantiated optimal cubic equation of state

The results related to the possibility of choosing the optimal cubic equations of state (ES) are presented. The study is carried out in the framework of a new model among three-term ES based on the molecular model of interacting point centers (IPC) and the well-known two-term ES of the van der Waals type. Manifestations of acting between molecules-points of attraction and repulsion forces are reflected in the structure and parameters of the ES belonging to the basic one-parameter family. The selection technique presented earlier was based on the possibility to obtain a consistent set of parameters that form the optimal equation. As a generalization of the limit variants of the ES with various manifestations of forces, a simple three-term four-parameter ES is proposed and investigated. All parameters make sense. Two relative parameters form the equation. It is shown that the known ES of Ishikawa, Chang, and Lu after the transformation become a special case of the ES of the IPC and cannot be considered as a general one. The technique was tested by calculating the critical isotherms of a number of substances, including argon, isopentane, carbon dioxide, etc. The next step should be to connect to the analysis a more finely structured control parameter.

Energy and CO2 Fluxes over Native Fields of Southern Brazil through Multi-Objective Calibration of INLAND Model

Land surface/ecosystem models (LSEMs) play a key role in understanding the Earth’s climate. They represent ecosystem dynamics by simulating fluxes occurring between the biosphere and atmosphere. However, for a correct flux simulation, it is critical to calibrate the model using robust and state-of-the-art calibration techniques. In this work, we optimize parameters of the Integrated Model of Land Surface Processes (INLAND) using the hierarchical multi-objective calibration method (AMALGAM) to improve the representation of surface processes in a natural ecosystem over the Pampa biome in South America. The calibration was performed using experimental data of energy and CO2 flux collected in a native field located in southern Brazil. We compared simulations using the default and calibrated parameter set. The results show that the calibration of the model significantly improved all fluxes analyzed. The mean errors and bias values were significantly reduced, and the seasonality of fluxes was better represented. This work is one of the first to apply a multi-objective calibration in an LSEM to represent surface fluxes in the Pampa biome, presenting a consistent set of parameters for future applications used in studies of biome land use and land cover.

Effect of statistically stored dislocations in tungsten on the irradiation induced nano-hardening analyzed by different methods

Tungsten self-ion irradiation was performed at 800 °C up to 0.01-1 dpa on two different W grades with essentially different dislocation density. Nanoindentation was applied to characterize the radiation hardening in two W grades with different microstructure. Different methods to analyze the indentation curves were applied to extract the bulk equivalent radiation hardening. It was shown that depending on the applied method, different outcomes may occur. The most satisfactory procedure was established and a consistent set of parameters was found. The bulk equivalent radiation hardening was found to saturate above 0.1 dpa. The characteristic distance between irradiation induced defects acting as dislocation pinning points was found to decrease up to 0.1 dpa, and then saturate/increase with irradiation dose. No essential difference in radiation hardening was observed between the studied W grades with essentially different initial dislocation density.

Superflares on the late-type giant KIC 2852961

Context. The most powerful superflares reaching 1039 erg bolometric energy are from giant stars. The mechanism behind flaring is thought to be the magnetic reconnection, which is closely related to magnetic activity (including starspots). However, it is poorly understood how the underlying magnetic dynamo works and how the flare activity is related to the stellar properties that eventually control the dynamo action. Aims. We analyze the flaring activity of KIC 2852961, a late-type giant star, in order to understand how its flare statistics are related to those of other stars with flares and superflares, and to understand the role of the observed stellar properties in generating flares. Methods. We searched for flares in the full Kepler dataset of KIC 2852961 using an automated technique together with visual inspection. We cross-matched the flare-like events detected by the two different approaches and set a final list of 59 verified flares during the observing term. We calculated flare energies for the sample and performed a statistical analysis. Results. The stellar properties of KIC 2852961 are revised and a more consistent set of parameters are proposed. The cumulative flare energy distribution can be characterized by a broken power law; that is to say, on the log-log representation the distribution function is fitted by two linear functions with different slopes, depending on the energy range fitted. We find that the total flare energy integrated over a few rotation periods correlates with the average amplitude of the rotational modulation due to starspots. Conclusions. Flares and superflares seem to be the result of the same physical mechanism at different energy levels, also implying that late-type stars in the main sequence and flaring giant stars have the same underlying physical process for emitting flares. There might be a scaling effect behind the generation of flares and superflares in the sense that the higher the magnetic activity, the higher the overall magnetic energy released by flares and/or superflares.

Molecular Coherent Three-Quantum Two-Dimensional Fluorescence Spectroscopy.

We introduce molecular coherent three-quantum (3Q) two-dimensional (2D) fluorescence spectroscopy with phase cycling via shot-to-shot pulse shaping at a 1 kHz repetition rate. This allows us to acquire simultaneously, within a single scan, three fourth-order and six sixth-order signals correlating various one-quantum, two-quantum, and 3Q coherences. We demonstrate the approach on the dye molecule rhodamine 700 and reproduce all nine 2D data sets, including their absolute signal strengths, with simulations using a single, consistent set of model parameters. We observe a linear concentration dependence of all nonlinear signals, evidencing the absence of cascades and many-particle signals of noninteracting molecules. The single-beam, background-free implementation allows direct comparability between various nonlinear signal types and provides information about multiple excited states. Apart from molecules, the method is expected to be applicable to supramolecular systems, polymers, and solid-state materials with the prospect of revealing signatures of bi- and triexcitonic states.

Line intensity parameters in the ν3 and 2ν3-ν3 bands of methyl chloride in the 13 µm region

We performed the systematic measurements of line intensities of ro-vibrational absorption transitions of the ν3 and 2ν3-ν3 parallel bands of 12CH335Cl and 12CH337Cl isotopes. The spectra were recorded in the spectral region between 650 and 800 cm−1 with a high-resolution Fourier transform spectrometer.A mono-spectrum fitting technique was used to fit a series of seven spectra at pressures of CH3Cl ranging from 1.02 to 10.24 mbar to retrieve line intensities of 2385 transitions of the two isotopic species. The measured line intensities are discussed in relation to rotational quantum numbers, and used to derive the square of the transition dipole moments for each line. The analysis of these moments allows us to derive a consistent set of line intensity parameters, such as vibrational transition moments, band intensities as well as Herman-Wallis coefficients for both bands. The results of the ν3 band are in satisfactory agreement with previous works and present databases, but a larger discrepancy (≈ 30%) is observed for the 2ν3-ν3 hot band.