High Kinetic Energy Research Articles

Zn, O Co-adsorption based on MOF-5 for efficient capture of radioactive iodine

The harmful effects of iodine in nuclear waste gas on humans and the environment, as well as the high kinetic energy of iodine molecules caused by the high-temperature environment, make it very important to develop and produce adsorbents with many active sites. The performance and mechanism of iodine capture by MOF-5 were investigated by experiments and molecular simulations for environmental protection. It was found that the synthesized MOF-5 can remove iodine from the gas phase and cyclohexane solution, with a high iodine capture capacity (0.63 g g-1) at 75 ℃. The cycling test illustrated the better recoverability and stability of MOF-5. The iodine capture capacity of MOF-5 in the liquid phase was 155 mg g-1, which is not the same as that of iodine in the gas phase. The multi-scale mechanistic analysis revealed that the adsorption process of MOF-5 on iodine was dominated by chemisorption, and the efficient capture of iodine was achieved by the co-adsorption of the central metal Zn atom and the tetrahedral apex O atom of MOF-5. This study provides insight into the iodine trapping process and adsorption mechanism, which is instructive for environmental protection engineering.

Validation of Field-Dependent Ion-Solvent Cluster Modeling via Direct Measurement of Cluster Size Distributions.

Ion mobility spectrometry is widely used in analytical chemistry, either as a stand-alone technique or coupled to mass spectrometry. Ions in the gas phase tend to form loosely bound clusters with surrounding solvent vapors, artificially increasing the collisional cross section and the mass of the ion. This, in turn, affects ion mobility and influences separation. Further, ion-solvent clusters play an important role in most ionization mechanisms occurring in the gas phase. Consequently, a deeper understanding of ion-solvent cluster association and dissociation processes is desirable to guide experimental design and interpretation. A few computational models exist, which aim to describe the amount of clustering as a function of the reduced electric field strength, bath gas pressure and temperature, and the chemical species probed. It is especially challenging to model ion mobility under high reduced electrical field strengths due to the nonthermal conditions created by the field. In this work, we aim to validate a recently proposed first-principles model by comparing its predictions with direct measurements of cluster size distributions over a range of 20-120 Td as observed using a High Kinetic Energy Ion Mobility Spectrometer coupled to a mass spectrometer (HiKE-IMS-MS). By studying H+(H2O)n, [MeOH + H + n(H2O)]+, [ACE + H + n(H2O)]+, and [PhNH2 + H + n(H2O)]+ as test systems, we find very good agreement between model and experiment, supporting the validity of the computational workflow. Further, the detailed information gained from the modeling yields important insights into the cluster dynamics within the HiKE-IMS, allowing for better interpretation of the measured ion mobility spectra.

Numerical assessment of stability behaviour in supercritical CO2 based NCLS configured with heater, heat exchanger and isothermal wall as heat source

Three-dimensional numerical analysis is presented in this study to assess the transient and stability behaviour of supercritical CO2 (sCO2) based NCLs configured with three different types of heat sources, i.e., heater, a hot heat exchanger (HHX) and isothermal wall (ISO) at the source, and a cold heat exchanger (CHX) at the sink in all three NCLs. Unsteady threedimensional conservation equations (mass, momentum and energy equations) are solved to assess the transient and stability behaviour of sCO2 mass flow rate, temperature and velocity as a function of time. Further, the effect of pressure on sCO2 mass flow rate is also assessed to compare the loops performance. Performance of the loop has been studied for various heat inputs at the source by keeping constant mass flow rate and temperature at the sink. It is observed that for any boundary condition at the source, the loop experiences some initial disturbances or instabilities before reaching the steady-state. However, the time needed to attain a steady-state varies with the nature of heat input employed at the source. Results show a higher magnitude of instabilities in the Heater-CHX loop than HHX-CHX and ISO-CHX loops, and these instabilities mitigate at a faster rate in the ISO- CHX loop at all levels of heat input and operating pressure of the loop. It is also observed that as loop fluid operating pressure increases, the instability of the system decreases and the loop fluid mass flow rate increases. Further, the Nusselt number in the Heater-CHX loop is more than other loops because of its high turbulent kinetic energy. The findings of this study are validated with the published experimental and numerical data and found a good agreement.

Turbulent characteristics in complex coastal areas assessed using BSWO observations and WRF-LES simulation results

Studies exploring the turbulent structure of the planetary boundary layer (PBL) over complex topographies are very limited, especially at night, because of the lack of available observations and difficulty of highly resolved simulation. In this study, micro-meteorological and turbulent characteristics over complex coastal areas were investigated based on high spatial-temporal resolution by using the Weather Research and Forecasting–Large Eddy Simulation (WRF-LES) model. Then, the simulations were compared to comprehensive observations obtained at the Boseong Standard Weather Observatory (BSWO), which is equipped with various observation facilities, such as a meteorological observation tower with a height of 307 m, and aiding ground-based remote sensing measurements used for PBL research. The comparison between the WRF-LES model results and the measurements by the wind lidar system at the BSWO showed that the LES approach in this study reproduced the spatial/vertical wind field structure and land-sea wind circulation distinctly better than the conventional PBL schemes. High turbulent kinetic energy (TKE) was observed near the surface level at night due to the increased nocturnal shear production following the evolution of land and mountain breezes. The calculated TKE from WRF-LES model was applied to identify the mixing intensity based on the mixing length and eddy diffusion coefficient within the boundary layer, and then those were evaluated with the observed extinction coefficient from the aerosol Micro-Pulse Lidar system (MPL). In addition, the planetary boundary layer height (PBLH) at night was explored by using the TKE threshold method combined with the bulk Richardson number threshold method for the daytime PBLH. Compared with the observed value from a ceilometer at the BSWO, we found that the TKE threshold method proposed in this study could yield highly accurate PBLH values, especially at night. It is also expected that the enhanced application of WRF-LES like to this study can lead to understanding and prediction with the high confidence for much detail and accurate spatiotemporal turbulent structure over complex coastal areas, which will contribute to more comprehensive air quality modeling studies.

Numerical simulation of the flow field and radiation noise from a pump-jet propulsor under various stator pre-whirl angles

The effects of different stator pre-whirl angles on the hydrodynamic and noise performance of a pump-jet propulsor (PJP) are studied; these angles are the inlet, outlet, and stagger angles. The stress-blended eddy simulation (SBES) approach, used to describe flow details around a PJP, is combined with the variational Lighthill's analogy to perform the acoustic calculation. The discrete peaks of the unsteady thrust of a single rotor blade and of all of the rotor blades are located at the harmonics of the blade passage frequency for stator (BPFs) and the blade passage frequency for rotor (BPFr), respectively. The trend in the amplitude with the pre-whirl angle at various harmonics follows no systematic rule, but the excessive pre-whirl angle increases the amplitude in the whole spectrum. With increases in pre-whirl angle, the stator sheet vortex and root vortex are weakened and enhanced, respectively, leading to a reduction of the high turbulent kinetic energy (Tk) regime at the root. Further study of the PJP sound indicates that the discrete tonal noise is located at the BPFs, BPFr, and their harmonics; the pre-whirl angle does not affect these locations, except in the largest inlet angle case. The cases with the least pre-whirl angle have an extremely low noise level, particularly at the outlet angle, which has an obvious downstream directivity.

Dissociative photoionisation of O2 with tunable 10, 20 and 30 eV photons

Atomic oxygen ions, O+, created by photoexcitation of a cold supersonic beam of O2 by the output of a free-electron laser operating in the 128–122 nm region are detected by sliced velocity map imaging. Analysis of the richly structured high resolution kinetic energy and angular distributions obtained show that O+ production is due to the second and third harmonics present in the laser output. Excellent slicing and optimal velocity mapping allows separation of overlapping signal from dissociative photoionisation processes driven by 20 eV versus 30 eV photons. A two-colour experiment combining the free electron laser and a nanosecond dye laser output at 225.6 nm allowed detection of direct photodissociation of the metastable O2 + b 4Σg - (v = 0–4) state is observed and assigned to a parallel b 4Σg - – (c 4Σu -)4s Rydberg transition followed by dissociation to O+ (4S) + O(3P2).

Application of High Kinetic Energy Buffer Control Technology after Free Recoil

Aiming at the problem of high recoil kinetic energy caused by launching long-range guided projectiles, the main effect and Pareto of barrel diameter, projectile mass, initial velocity and charge on recoil kinetic energy are studied based on Latin hypercube test design under certain bore pressure conditions, which provides reference for the evaluation and control of high recoil kinetic energy brought by new ammunition. At the same time, in order to solve the difficulty of free recoil high kinetic energy buffer braking, four mathematical models and technical schemes of recoil buffer braking are introduced and designed, and the buffer characteristics are compared and analyzed. Based on the analysis of reducing the buffer force and the length of recoil motion, a free recoil test bench scheme for the combination of blocking cables and recoil buffer devices is also proposed. The recoil braking force is planned based on NCGA intelligent optimization algorithm. The results show that the combined buffer braking principle is feasible and the buffer effect is good.

A Collapsar Origin for GRB 211211A Is (Just Barely) Possible

Gamma-ray bursts (GRBs) have historically been divided into two classes. Short-duration GRBs are associated with binary neutron star mergers (NSMs), while long-duration bursts are connected to a subset of core-collapse supernovae (SNe). GRB 211211A recently made headlines as the first long-duration burst purportedly generated by an NSM. The evidence for an NSM origin was excess optical and near-infrared emission consistent with the kilonova observed after the gravitational-wave-detected NSM GW170817. Kilonovae derive their unique electromagnetic signatures from the properties of the heavy elements synthesized by rapid neutron capture (the r-process) following the merger. Recent simulations suggest that the “collapsar” SNe that trigger long GRBs may also produce r-process elements. While observations of GRB 211211A and its afterglow rule out an SN typical of those that follow long GRBs, an unusual collapsar could explain both the duration of GRB 211211A and the r-process-powered excess in its afterglow. We use semianalytic radiation transport modeling to evaluate low-mass collapsars as the progenitors of GRB 211211A–like events. We compare a suite of collapsar models to the afterglow-subtracted emission that followed GRB 211211A, and find the best agreement for models with high kinetic energies and an unexpected pattern of 56Ni enrichment. We discuss how core-collapse explosions could produce such ejecta, and how distinct our predictions are from those generated by more straightforward kilonova models. We also show that radio observations can distinguish between kilonovae and the more massive collapsar ejecta we consider here.

A Method for Transmitting Spacecrafts in Space with Velocity of at Least 0.01 of the Light Speed Using Materials with Very High Kinetic Energy in High Electric Fields

A Method for Transmitting Spacecrafts in Space with Velocity of at Least 0.01 of the Light Speed Using Materials with Very High Kinetic Energy in High Electric Fields

Numerical simulation on transport behavior of gradated coarse particles in deep-sea vertical pipe transportation

Flow pattern and hydrodynamic characteristics of coarse particles in deep-sea hydraulic lifting pipes are simulated using a numerical approach developed by combining the computational fluid dynamics method with a discrete element method in the Euler–Lagrange framework. This paper examines the effects of feed concentration, two-phase flow initial mixture velocity, and particle gradation on the dynamic characteristics of particles and flow pattern in the pipe by validating the rationality of numerical simulation. The results demonstrate that particles are distributed from the pipe center to the pipe wall, while the lift force causes more particles to be distributed in the pipe center. Moreover, greater inertia makes large particles more concentrated in the center. Particle-induced turbulence modifies the lift force and causes particles to move from the pipe center to its wall. Due to the increasing trend of lift force, particles gather toward the center of the pipe at an increasing pace as the initial velocity increases. The greater the feed concentration, the more particles disperse toward the pipe wall due to the violent momentum exchange caused by the high concentration and the significantly altered lift force caused by the high turbulent kinetic energy resulting from a high concentration. From the particle gradation 1:1:1 to 1:6:1, the pressure drop decreases gradually as the reduction in small particles decreases the number of particles near the wall, and the frictional energy loss between the particles and the pipe wall decreases.

A High Kinetic Energy Ion Mobility Spectrometer for Operation at Higher Pressures of up to 60 mbar

High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) are usually operated at absolute pressures around 20 mbar in order to reach high reduced electric field strengths of up to 120 Td for influencing reaction kinetics in the reaction region. Such operating points significantly increase the linear range and limit chemical cross sensitivities. Furthermore, HiKE-IMS enables ionization of compounds normally not detectable in ambient pressure IMS, such as benzene, due to additional reaction pathways and fewer clustering reactions. However, operation at higher pressures promises increased sensitivity and smaller instrument size. In this work, we therefore study the theoretical requirements to prevent dielectric breakdown while maintaining high reduced electric field strengths at higher pressures. Furthermore, we experimentally investigate influences of the pressure, discharge currents and applied voltages on the corona ionization source. Based on these results, we present a HiKE-IMS that operates at a pressure of 60 mbar and reduced electric field strengths of up to 105 Td. The corona experiments show shark fin shaped curves for the total charge at the detector with a distinct optimum operating point in the glow discharge region at a corona discharge current of 5 μA. Here, the available charge is maximized while the generation of less-reactive ion species like NOx+ is minimized. With these settings, the reactant ion population, H3O+ and O2+, for ionizing and detecting nonpolar substances like n-hexane is still available even at 60 mbar, achieving a limit of detection of just 5 ppbV for n-hexane.

Plasma activation mechanisms governed by specific energy input: Potential and perspectives

AbstractIn a low‐temperature plasma, the electrons pick up energy from the electric field in collisions with atoms and molecules, gaining high kinetic energy that must be sufficient for ionizing reactions to sustain the plasma. For molecular gases, an average energy per heavy gas particle is thus available in the plasma, the specific energy input, yielding plasma activation by inelastic collisions. Following a distribution law, the probability for the activation mechanism can be described by an Arrhenius‐like equation. The potential of this approach is demonstrated on the basis of plasma polymerization and plasma CO2conversion. For perspective, energy efficiencies are discussed as a function of conversion indicating the optimum that can be achieved by electron impact activation compared with additional ways of energy transfer, probably depending on certain constraints.

Highly Occupied Surface States at Deuterium-Grown Boron-Doped Diamond Interfaces for Efficient Photoelectrochemistry.

Polycrystalline boron-doped diamond is a promising material for high-power aqueous electrochemical applications in bioanalytics, catalysis, and energy storage. The chemical vapor deposition (CVD) process of diamond formation and doping is totally diversified by using high kinetic energies of deuterium substituting habitually applied hydrogen. The high concentration of deuterium in plasma induces atomic arrangements and steric hindrance during synthesis reactions, which in consequence leads to a preferential (111) texture and more effective boron incorporation into the lattice, reaching a one order of magnitude higher density of charge carriers. This provides the surface reconstruction impacting surficial populations of CC dimers, CH, CO groups, and COOH termination along with enhanced kinetics of their abstraction, as revealed by high-resolution core-level spectroscopies. A series of local densities of stateswerecomputed, showing a rich set of highly occupied and localized surface states for samples deposited in deuterium, negating the connotations of band bending. The introduction of enhanced incorporation of boron into (111) facet of diamond leads to the manifestation of surface electronic states below the Fermi level and above the bulk valence band edge. This unique electronic band structure affects the charge transfer kinetics, electron affinity, and diffusion field geometry critical for efficient electrolysis, electrocatalysis, and photoelectrochemistry.

Probing heavy-ion collisions with the yield ratios of neutron-proton at intermediate energy

Within an isospin- and momentum-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model, we investigate effects of nucleon-nucleon short-range correlations (SRCs) and the nuclear symmetry energy on the yield ratios of neutron-proton (n/p) in four reaction systems K94r+94Kr, Z94r+94Zr, M94o+94Mo and R94u+94Ru. It is found that effects of the symmetry energy and the high momentum tails (HMTs), caused by the SRCs of nucleon-nucleon in the target and projectile, on the kinetic energy distribution of n/p yield ratio are almost same in four reaction systems. While the effect of the HMTs on the double ratio of n/p from neutron-rich and neutron-deficient reaction systems K94r+94Kr and R94u+94Ru is enlarged, and it is about two times than that of the symmetry energy in the high kinetic energies. Meanwhile, we find that the dependence of isospin-fractionation (i.e., the double ratio of n/p of gas-liquid phase) on the isospin asymmetry of reaction system is completely not sensitive to the HMTs but keeping high sensitivity to the symmetry energy. It indicates that the distribution of isospin-fractionation on the isospin asymmetry of reaction system can be taken as an experimental observable to extract information on nuclear symmetry energy.

Vibration Characteristics of a Tubular Turbine Prototype at Different Heads with Considering Free Surface and Water Gravity

Tubular turbines are widely used in low water head and tidal power development due to their straight flow path, simple structure, and wide efficient area. However, the severe vibration during actual operation greatly affects the safe operation of the tubular turbine. This study performs a numerical calculation of the tubular turbine, which meets the actual machine conditions considering the free surface and water gravity; compares and analyzes the flow characteristics and pressure fluctuation spectrum characteristics in the tubular turbine under different water heads; and verifies the comparison with the actual machine test results to explore the vibration characteristics and vibration mechanism of the tubular turbine. Research results show that a large pressure difference is observed between the top and bottom of the runner chamber, and the runner needs to experience large periodic pressure fluctuations during rotation due to the combined effect of hydrostatic pressure and hydrodynamic pressure. Under different water heads, obvious flow turbulence and high turbulent kinetic energy areas are observed in the runner and draft tube due to the influence of the shape of the blade wake vortex. The vibration in the tubular turbine is mainly concentrated in the runner and draft tube and influenced by the water gravity and the runner structure of the transverse cantilever beam. The amplitude of pressure fluctuation is the largest when the frequency inside the runner is the blade passing frequency at each water head, so the maximum vibration position is located at the runner. The research results serve as a guide for the design and operation of the horizontal tubular turbine.

Fabrication of highly porous and adhesive thick Y2O3 film by room-temperature spray process for thermal insulation coating

An effective strategy for manufacturing ceramic thick films with high porosity and robustness was proposed by aerosol deposition (AD). The agglomeration of the Y2O3 and polyethylene powder composites was investigated to prepare porous films. After exploring a suitable particle distribution, Y2O3 and polyethylene composite powder were prepared using two different mixing methods with various polyethylene contents. During the transportation in vacuum, easily separated mixture powders of Y2O3 and polyethylene caused insufficient energy result in partially delaminated films. In contrast, the appropriate agglomeration of the Y2O3–polyethylene composite powders can be crushed with higher kinetic energy by increased mass, resulting in uniform and robust porous films with high adhesive strength. After burning, the Y2O3–polyethylene (8 wt% polyethylene) thick film (∼100 μm) exhibited high porosity (66%), low thermal conductivity (∼0.15 W/m·K at room temperature), and good adhesion strength (8.4 MPa). In this study, we provide effective guidelines for fabricating AD-based porous ceramic films deposited at room temperature with low thermal conductivity and high adhesive strength.

Design and Computational Analysis of the Conventional Vaned Diffuser for a Turbocharger Compressor

Abstract: A review of a study paper on centrifugal compressors revealed that the flow dynamics within them are extremely complex. The intensity of secondary flows and tip leakage flows will significantly alter depending on the vane loading, creating the low energy fluid zone on the impeller blade's suction surface. The flow finally becomes excessively viscous and non-uniform at the centrifugal impeller's exit due to this type of flow pattern. The goal of the current work is to comprehend the flow at the centrifugal impeller's exit and construct the conventional vaned diffuser (CVD) in accordance with that understanding in order to transfer the high kinetic energy already existing into a static pressure rise. A highly loaded centrifugal compressor with a newly developed conventional vaned diffuser (CVD) was subjected to numerical analysis using Ansys for an impeller tip mach number of 0.9. For design and off-design positions, respectively, key diffuser performance characteristics like pressure ratio and static pressure recovery are studied numerically, as qualitatively was Mach number. The pressure recovery of conventional vaned diffuser was showing 39.1 % more than the compressor with vaneless diffuser

Improving the Usage Properties of Steel Using Cold Spray Deposition: A Review

In this paper, the improvement of the characteristics of different steels that are subjected to extreme operating conditions, including the steels used in the manufacture of various military components, the AISI 52100, the manufacture of bearings, and other types of parts that are also subjected to severe operating conditions were analyzed regarding cold spraying, which uses different types of powders to increase the performance of the materials. The cold, thermal spraying technology “Cold Spray” is a method of processing particles in a solid state. Thermal spraying, based on the dynamic increase in gas acceleration up to supersonic speeds, leads to the obtainment of high kinetic energies, and the accelerated particles are deposited at values that are below their melting point. Research conducted through cold spray technology has seen a significant improvement in material properties; when processing the particles in a solid state, they adhere to the surface instead of eroding it. Cold spraying has proven to be an effective technique for improving material properties, as confirmed by its integration into different fields and industries, becoming competitive by being the only method for depositing particles below their melting point.

Tutorial: Modeling of the extraction and acceleration of negative ions from plasma sources using particle-based methods

In this Tutorial, we consider plasma sources with applications to fusion devices and high energy accelerators. These ion sources typically produce negative ions from hydrogen-isotope gases, which are extracted through one or multiple apertures and accelerated to high kinetic energies. Next, they are either double stripped of two electrons to form positive ions used as precursors in accelerator devices or neutralized to produce a neutral beam injected in tokamak reactors. Contrary to the working conditions of most ion sources where volume production prevails, the mechanism of negative ion production by dissociative electron attachment on vibrationally excited molecules inside the plasma volume of fusion-type hydrogen-fueled high power discharges is mostly balanced by their destruction by detachment before being extracted rendering this means of producing negative ions rather inefficient. Surface production through the transfer of electrons from low work function metallic materials to the impacting atoms is the alternative solution to fulfill the requirements for the applications concerned. Negative ions are produced close to the aperture from which they are extracted. As a result, the analysis and understanding of the extraction mechanisms through experimental diagnostics is rather difficult due to the lack of accessibility and can only give a partial view. In addition, most of the experimental work is focused on the validation of requirements for the applications and not to the investigation of the fundamental processes that take place inside these types of sources. This Tutorial is focused on the description and understanding of the physical mechanisms behind the extraction and acceleration of negative ions from hydrogen plasma sources through modeling methods. We describe the numerical techniques of particle-based methods with a specific emphasis on particle-in-cell Monte Carlo collision algorithms. An analysis of the physical processes involved in driving the negative ions from the plasma source, across the apertures and inside the accelerator as reported in the literature, is presented in detail. This Tutorial concludes with additional and future works to be addressed in the coming years.

Визначення впливу газодинамічних параметрів струменя на ступінь деформації частинок під час електродугового напилення

The paper analyzes the scientific and technical information on the process of propagation of a heterophase turbulent jet with particles of the solid phase during electric arc spraying. It has been established that data on determining the parameters of impact and deformation of sprayed particles are currently incomplete, which is of great importance when choosing the optimal temperature-time parameters for the subsequent heat treatment of the formed coatings. The calculation of the main gas-dynamic parameters for electric arc spraying was carried out: the velocity of air and sprayed particles along the jet axis and along its cross section at a spraying distance of 100 mm. It has been established that the air velocity in the initial section of the jet is constant and is about 310 m/s. At a distance of about 35 mm, this section ends and the air velocity begins to decrease and at a spraying distance of 100 mm it is 135 m/s. It is shown that in the initial section of the jet, the sprayed particles are accelerated and reach a maximum velocity of about 80 m/s. With a further increase in the distance from the nozzle exit, the particles gradually lose speed and at a spraying distance of 100 mm it is about 75 m/s. Based on the determination of the surface tension, the average drop size of the Sv-08G2S wire was calculated upon separation from the electrode (214 μm) and on approaching the substrate (82 μm). Taking into account the data obtained, a calculated determination of the deformation degree of the sprayed particles along the spraying spot at a distance of 100 mm was made. It has been established that particles along the flow axis have the highest degree of deformation (about 86 %), which is explained by their high kinetic energy. The average value of the diameter of sprayed particles at a distance of 100 mm was experimentally determined when spraying Sv-08G2S wire (84 µm) into water, which correlates well with the calculated value. A cross section was prepared and the degree of particle deformation along the spray spot was determined. A comparative analysis of the calculated and experimental data on the degree of particle deformation was carried out, which showed the difference between them to be no more than ±1 %.