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[Display omitted] • Reactions of bis(cyclopentadienyl) ruthenium (ruthenocene, RuCp 2) and cyclopentadienyl pyrrolyl ruthenium (RuCpPy) on the hydroxylated surface were explored by density functional theory calculations. • Ru precursors, such as bis(pyrrolyl) ruthenium (RuPy 2), were designed for H 2 O-based atomic layer deposition of RuO 2 · x H 2 O. • New cascade mechanism of H 2 O-based atomic layer deposition of RuO 2 · x H 2 O was proposed. As the unique nanofabrication technique, atomic layer deposition (ALD) can be used to deposit high-quality, uniform, and conformal nanoparticle coatings. Ru and its oxides (RuO x) are important materials in the fields of microelectronics and catalysis. In this work, the reaction of Ru precursors with different ligands on the hydroxylated surfaces were explored. The elimination of the pyrrolyl (Py) ligand is easier than that of the cyclopentadienyl (Py) ligand on the hydroxylated surface. The reaction involved in RuO 2 · x H 2 O ALD using RuPy 2 and H 2 O as precursors was further investigated. During the RuPy 2 reaction, the pyrrolyl ligand is eliminated by the substitution reaction with a surface hydroxyl group. However, the desorption of the pyrrole molecule is difficult due to the strong adsorption between the pyrrole molecule and Ru surface. During the H 2 O reaction, the H 2 O molecules further help the elimination of pyrrolyl ligands from the surface and the dissociative desorption of pyrrole molecules This unique reaction mechanism involved in the ALD of RuO 2 with the assistance of H 2 O can be termed new cascade mechanism. These findings provide theoretical guidance for precursor design and ALD growth of metal oxides. [ABSTRACT FROM AUTHOR]

Abstract The effect of nuclear interactions on measurable net-proton number fluctuations in heavy ion collisions at the SIS18/GSI accelerator is investigated. The state of the art UrQMD model including interaction potentials is employed. It is found that the nuclear forces enhance the baryon number cumulants, as predicted from grand canonical thermodynamical models. The effect however is smeared out for proton number fluctuations due to iso-spin randomization and global baryon number conservation, which decreases the cumulant ratios. For a rapidity acceptance window larger than Δ y > 0.4 the effects of global baryon number conservation dominate and all cumulant ratios are significantly smaller than 1. [ABSTRACT FROM AUTHOR]

Background: The nuclear incompressibility ( K 0 ) plays a crucial role in understanding diverse phenomena in nuclear structure and reactions, as well as in astrophysics. Heavy-ion-collision measurements in combination with transport model simulations serve as important tools for extracting the nuclear incompressibility. However, uncertainties in transport models (or model dependence) partly affect the reliability of the extracted result. Purpose: In the present work, by using the recently measured data of rapidity-dependent flows, we constrain the incompressibility of nuclear matter and analyze the impact of model uncertainties on the obtained value. Method: The method is based on the newly updated version of the ultrarelativistic quantum molecular dynamics (UrQMD) model in which the Skyrme potential energy-density functional is introduced. Three different Skyrme interactions which give different incompressibilities varying from K 0 = 201 to 271 MeV are adopted. The incompressibility is deduced from the comparison of the UrQMD model simulations and the FOPI data for rapidity-dependent elliptic flow in Au + Au collisions at beam energies 0.4 A –1.0 A GeV. Results: The elliptic flow v 2 as a function of rapidity y 0 can be well described by a quadratic fit v 2 = v 20 + v 22 ⋅ y 0 2 . It is found that the quantity v 2 n defined by v 2 n = | v 20 | + | v 22 | is quite sensitive to the incompressibility K 0 and the in-medium nucleon–nucleon cross section, but not sensitive to the slope parameter L of the nuclear symmetry energy. Conclusions: With the FU3FP4 parametrization of the in-medium nucleon–nucleon cross section, an averaged K 0 = 220 ± 40 MeV is extracted from the v 2 n of free protons and deuterons. However, remaining systematic uncertainties, partly related to the choice of in-medium nucleon–nucleon cross sections, are of the same magnitude ( ± 40 MeV ). Overall, the rapidity dependent elliptic flow supports a soft symmetric-matter equation-of-state. [ABSTRACT FROM AUTHOR]

Within the ultrarelativistic quantum molecular dynamics (UrQMD) model, by reversely tracing nucleons that are finally emitted at mid-rapidity (| y 0 | < 0.1) in the entire reaction process, the time evolution of elliptic flow (v 2) of these traced nucleons is studied in Au+Au collisions at beam energy of 0.4 GeV/nucleon with different impact parameters. The initial value of v 2 is positive and increases with impact parameter, it then decreases as time passes and tends to saturate at a negative value. It is found that nucleon-nucleon collisions always suppress the value of v 2 (enhance the out-of-plane emission), while the nuclear mean field potential effect is more complex, which depends on both impact parameter and reaction time. The most relevant density probed by v 2 of nucleons at mid-rapidity is found to be ∼ 60% of the maximum density reached during the collisions. [ABSTRACT FROM AUTHOR]

Inferences of the nuclear symmetry energy from heavy-ion collisions are currently based on the comparison of measured observables and transport model simulations. Only the expectation values of observables over all considered events are used in these approaches, however, observables can be obtained event-by-event both in experiments and transport model simulations. By using the light gradient boosting machine (LightGBM), a modern machine-learning algorithm, we present a framework for inferring the density-dependent nuclear symmetry energy from observables in heavy-ion collisions on the event-by-event analysis. The ultrarelativistic quantum molecular dynamics (UrQMD) model simulations are used as training data. The symmetry energy slope parameter extracted with LightGBM event-by-event from test data also by UrQMD has an average spread of approximately 30 MeV from the truth, and is found to be robust against variations in model parameters. In addition, LightGBM can identify features that have the greatest effect on the physics of interest, thereby offering valuable insights. Our study suggests that the present framework can be a powerful tool and may offer a new paradigm to study the underlying physics in heavy-ion collisions. [ABSTRACT FROM AUTHOR]

A systematic study of the in-medium correction factor (F) on nucleon-nucleon elastic cross section is performed within the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model. The effects of the beam energy dependence of F on the directed, elliptic flow and nuclear stopping in 197Au+197Au collisions with energy ranging from 0.09 to 0.8 A GeV are explored. It is found that the directed, elliptic flow and nuclear stopping at relatively low energies are very sensitive to F , and the sensitivity gradually weakens with increasing beam energy. The beam energy dependent in-medium correction factor F is deduced from the comparison of the excitation functions of the directed, elliptic flow and nuclear stopping between the calculated results and the FOPI experimental data. [ABSTRACT FROM AUTHOR]

A deep convolutional neural network (CNN) is developed to study symmetry energy (E sym (ρ)) effects by learning the mapping between the symmetry energy and the two-dimensional (transverse momentum and rapidity) distributions of protons and neutrons in heavy-ion collisions. Supervised training is performed with labeled data-set from the ultrarelativistic quantum molecular dynamics (UrQMD) model simulation. It is found that, by using proton spectra on event-by-event basis as input, the accuracy for classifying the soft and stiff E sym (ρ) is about 60% due to large event-by-event fluctuations, while by setting event-summed proton spectra as input, the classification accuracy increases to 98%. The accuracies for 5-label (5 different E sym (ρ)) classification task are about 58% and 72% by using proton and neutron spectra, respectively. For the regression task, the mean absolute errors (MAE) which measure the average magnitude of the absolute differences between the predicted and actual L (the slope parameter of E sym (ρ)) are about 20.4 and 14.8 MeV by using proton and neutron spectra, respectively. Fingerprints of the density-dependent nuclear symmetry energy on the transverse momentum and rapidity distributions of protons and neutrons can be identified by convolutional neural network algorithm. [ABSTRACT FROM AUTHOR]

It is shown that the inclusion of hadronic interactions, and in particular nuclear potentials, in simulations of heavy ion collisions at the SPS energy range can lead to obvious correlations of protons. These correlations contribute significantly to an intermittency analysis as performed at the NA61 experiment. The beam energy and system size dependence is studied by comparing the resulting intermittency index for heavy ion collisions of different nuclei at beam energies of 40 A , 80 A and 150 A GeV. The resulting intermittency index from our simulations is similar to the reported values of the NA61 collaboration, if nuclear interactions are included. The observed apparent intermittency signal is the result of the correlated proton pairs with small relative transverse momentum Δ p t , which would be enhanced by hadronic potentials, and this correlation between the protons is slightly influenced by the coalescence parameters and the relative invariant four-momentum q i n v cut. [ABSTRACT FROM AUTHOR]

The elliptic flow ratio of neutrons versus protons in heavy-ion collisions (HICs) is one of the important probes to constrain the nuclear symmetry energy, however measuring the flow of neutrons with high precision is a great challenge for experimental techniques. In this work, the elliptic flow of protons is studied and it is found that the rapidity at which the sign of v 2 changes from negative to positive is sensitive to the density dependence of the symmetry energy. By comparing the existing FOPI experimental data for proton flows to the calculations with the ultrarelativistic quantum molecular dynamics (UrQMD) model, the slope parameter of the nuclear symmetry energy is extracted to be L 0 = 43 ± 20 MeV at 95% confidence level. This is in good agreement with many recent results from investigations of nuclear structure properties and also partly overlaps with the recent result of the ASY-EOS experiment. [ABSTRACT FROM AUTHOR]

Machine learning was used to predict the effective diffusion coefficient of radionuclides in compacted bentonites to reduce the cost of experimental methods. Through-diffusion experiments were conducted to determine the effective diffusion coefficient of Re(VII), which was used as a surrogate for 99Tc(VII), in compacted Anji bentonite. Five parameters (the external surface area, the ionic strength, the mass ratio of montmorillonite, the compacted dry density, and the accessible porosity) that affect the effective diffusion coefficient were calculated by a multi-porosity model to generate data for the analysis of the machine learning models to overcome the limited experimental data. The effective diffusion coefficient was predicted using two popular machine learning models, the Light Gradient Boosting Machine and Artificial Neural Network models, where the former exhibited higher sensitivity and accuracy in the prediction than the latter. The performance of the machine learning models was validated by comparing the experimental effective diffusion coefficients between this study and previous studies. The present work revealed that the machine learning method can be a powerful tool and may offer a new means of studying the effective diffusion coefficient. • Effective diffusion coefficient was predicted by machine learning models. • Through-diffusion method measured the effective diffusion coefficient of Re(VII). • Dataset was generated by multi-porosity model. • Light Gradient Boosting Machine outperformed Artificial Neutral Network. [ABSTRACT FROM AUTHOR]

• Porous single-crystal NTP micro-sized framework coated with conductive carbon nano-layer (NTP@C) is designed. • The carbon coating enhances conductivity of NTP@C, and protects it from O2 erosion serves as a protective phase. • Regulations in both the dissolved O2 content and pH values of aqueous Na2SO4 electrolyte are conducted. • The NTP@C displays superb electrochemical properties in the optimized Na2SO4 electrolyte (N2 purged and pH = 8.0). • The NTP@C based full devices exhibit high energy density and cycling stability with the optimum electrolyte. NASICON-type NaTi 2 (PO 4) 3 (NTP) is one of the most competitive anode materials for aqueous sodium-ion batteries (ASIBs), thanks to its unique three-dimensional open framework structure, high ionic conductivity and good chemical stability. However, the low electrical conductivity of NTP and the oxygen reduction induced side reactions seriously affect its practical applications. To well address the above issues, the synergistic regulation strategy in electrode materials and electrolytes is motivatively put forward. The porous single-crystal NTP micro-sized framework coated with conductive carbon nano-layer (denoted as NTP@C) is designed with significantly improved electronic conductivity and structural stability. With further regulations in both the dissolved oxygen content and pH values of aqueous Na 2 SO 4 electrolyte, the enhanced reversible capacities and cyclic stability especially at high rates are achieved by effectively alleviating side reactions. As a result, the fabricated NTP@C anode is optimized with a high-rate capability and remarkable long-duration electrochemical stability in the N 2 -purged aqueous Na 2 SO 4 electrolyte with pH = 8.0. Furthermore, the assembled NTP@C//Na 0.44 MnO 2 ASIBs exhibit high energy density of ∼40.0 Wh kg‒1 along with excellent cycling stability. More significantly, our work provides an insightful guideline for rational construction of other advanced aqueous rechargeable batteries. Hierarchical porous single-crystal NaTi 2 (PO 4) 3 @C framework is first designed, and exhibits enhanced electrochemical Na+-storage properties in half/full cells with detailed regulation in both the dissolved oxygen content and pH values of electrolytes, when evaluated a competitive anode platform for aqueous sodium-ion batteries. [Display omitted] [ABSTRACT FROM AUTHOR]

Within two different frameworks of isospin-dependent transport model, effect of nuclear symmetry energy at supradensities on the isospin-fractionation (IsoF) was investigated. With positive/negative symmetry potential at supradensities (i.e., values of symmetry energy increase/decrease with density above saturation density), for energetic nucleons, the value of neutron to proton ratio of free nucleons is larger/smaller than that of bound nucleon fragments. Compared with extensively studied quantitative observables of nuclear symmetry energy, the normal or abnormal isospin-fractionation of energetic nucleons can be a qualitative probe of nuclear symmetry energy at supradensities. [ABSTRACT FROM AUTHOR]

The effects of the exit convergent ratio on the propagation behavior (i.e., initiation processes and propagation characteristics) of rotating detonations utilizing liquid kerosene have been experimentally investigated by varying the exit convergent ratio from 1 to 10 (i.e., CR = 1, 1.25, 1.67, 2.5, 5 and 10) and the mass flow rate of oxidizer. Oxygen-enriched air with an oxygen volume fraction of 40% and kerosene have been used as oxidizer and fuel, respectively, which are supplied into the combustion chamber through an atomizer-slit configuration. Experimental results indicate that rotating detonation waves can be initiated and propagate with different propagation modes under different exit convergent ratios. Three different propagation modes have been obtained, i.e., a deflagration mode, an ignition failure mode and a stable detonation mode. Moreover, the results show that the convergent ratio significantly influences the propagation modes, and when the combustion chamber outlet with a smaller convergent ratio is employed, stable rotating detonation waves can be obtained easily. In addition, it is observed that the time of establishment of the detonation wave increases with the convergent ratio. • Effects of the exit convergent ratio on the propagation characteristics have been studied. • Three fundamental operating modes have been observed at different conditions. • Stable rotating detonations can be obtained easily with a smaller convergent ratio. • The influence of the exit convergent ratio on the initiation time has been investigated. [ABSTRACT FROM AUTHOR]

Nanopore electrochemical sensors have been developed to detect various emerging pollutants at the single-molecule level with high sensitivity and specificity due to their high resolution in past three decades, which is of great significance for emerging hazardous pollutants control. Electrochemical detection methods based on nanopore technology are primarily divided into two categories: resistive-pulse and rectification sensing. The main detection mechanism of the resistive-pulse method is based on the volume exclusion effect generated when the analyte enters through the nanopore, and it involves three primary detection strategies. The first approach involves nanopore technology for direct pollutant detection, where pollutant structure and concentration information is assessed based on nanopore-generated ionic current's blockade strength, duration, and frequency. The second strategy relies on weak intermolecular interactions when direct detection of pollutants is challenging. Molecular probes interact with target molecules to enhance detection sensitivity and achieve specific recognition. The third strategy is based on the biological/chemical reaction of pollutant molecules, through indirect detection method to achieve specific detection of target pollutant molecules. Additionally, relies on changes in surface charge polarity or nanopore spatial structure induced by the analyte molecules to achieve the detection of target molecules within the nanopore. This work demonstrates the research progress achieved in the application of nanopore electrochemical sensing technology to high-sensitivity detection of hazardous pollutants, utilizing the unique confined spatial characteristics of nanopores, combined with biorecognition techniques and principles of electrochemical reactions. [ABSTRACT FROM AUTHOR]

Abstract To explore an effective way for the nozzle design of a pulse detonation rocket engine (PDRE), theoretical and experimental researches have been carried out. The exhaust process and optimal converging/diverging area ratios of a nozzle were theoretically analyzed. Pressure and velocity fluctuations of the exhaust flow were considered to be the major issues. A fluidic solution which employs nitrogen flows in the nozzle throat and divergent section has been tested. The fluidic nozzle is able to adjust the effective area ratios according to the incoming flow. The effective convergent area ratio varied from 2.0 to 2.2, and the divergent one varied from 5.0 to 1.8. It is proved that the fluidic nozzle effectively improved the propulsive performance of the engine. A maximum average thrust increase of 137.8% was obtained in proper conditions. Highlights • A key-points nozzle design method for the PDRE was carried out. • Effect of a fluidic nozzle on the propulsive performance of a PDRE was validated. • Thrust and specific impulses were discussed in details. [ABSTRACT FROM AUTHOR]

To reduce hardware complexity and increase operating frequency, a simplified double-frequency scheme has been developed to obtain high-frequency detonations for pulse detonation rocket engines based on the valved and valveless schemes. This study focuses on characteristics of this simplified scheme. The critical points where detonations transit to deflagrations are considered at different operating conditions to clarify the lower boundaries of stable operations. Experimental results indicate that an ideal buffer zone may not be formed similar to the traditional valved schemes. Comparisons with the valveless scheme without the purge process show that the upper limits of oxidizer percentages are consistent to ensure stable operations, which implies that the present scheme operates potentially as the valveless mode. Detailed studies on the employed solenoid valves and impacts of retonations on the upstream passages demonstrate that solenoid valves are not able to realize intermittent supply control effectively. It is concluded that practical operations utilizing solenoid and rotary valves to control periodic supplies may also operate under a valveless scheme actually with a different upper limit of oxygen percentage in oxidizer. [ABSTRACT FROM AUTHOR]

To provide preferable operating conditions for biomass carbonization, the carbonization properties of maize straw, cotton stalk and poplar wood were investigated in nitrogen atmosphere by segmented heating process at different final temperatures of 300–800 °C for 1 h. Segmented heating carbonization contributes to higher ratio of mass and energy yields than a constant temperature/linear heating process with final temperature of around 300 °C. The fuel properties and characteristics of raw and carbonized biomass were analysed systematically. Increasing carbonization temperature, the fuel ratios of the obtained chars rise exponentially, and the profile of atomic H/C ratio versus atomic O/C ratio approximately decreases linearly. There are small changes of sulphur and nitrogen content in the chars. To provide an estimation method for higher heating value for torrefied/carbonized biomass, a new correlation is proposed based on ultimate analysis. The correlation is H H V = 19.9579 + 0.1284 C + 0.3355 H − 0.1209 O − 1.3836 N − 5.4680 S , which is validated through experimental data. The correlation has a low level of errors, that the correlation efficient, mean absolute error, average absolute error and average bias error are 0.971, − 6.75 × 10 − 6 MJ, 1.2% and 0.02% respectively. This work will make a contribution to the biomass pretreatment process. [ABSTRACT FROM AUTHOR]