Global hybrid simulations of soft X-ray emissions in the Earth’s magnetosheath

Earth’s magnetopause is a thin boundary separating the shocked solar wind plasma from the magnetospheric plasmas,and it is also the boundary of the solar wind energy transport to the magnetosphere.Soft X-ray imaging allows investigation of the large-scale magnetopause by providing a two-dimensional(2-D)global view from a satellite.By performing 3-D global hybrid-particle-in-cell(hybrid-PIC)simulations,we obtain soft X-ray images of Earth’s magnetopause under different solar wind conditions,such as different plasma densities and directions of the southward interplanetary magnetic field.In all cases,magnetic reconnection occurs at low latitude magnetopause.The soft X-ray images observed by a hypothetical satellite are shown,with all of the following identified:the boundary of the magnetopause,the cusps,and the magnetosheath.Local X-ray emissivity in the magnetosheath is characterized by large amplitude fluctuations(up to 160%);however,the maximum line-of-sight-integrated X-ray intensity matches the tangent directions of the magnetopause well,indicating that these fluctuations have limited impact on identifying the magnetopause boundary in the X-ray images.Moreover,the magnetopause boundary can be identified using multiple viewing geometries.We also find that solar wind conditions have little effect on the magnetopause identification.The Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)mission will provide X-ray images of the magnetopause for the first time,and our global hybrid-PIC simulation results can help better understand the 2-D X-ray images of the magnetopause from a 3-D perspective,with particle kinetic effects considered.

Hybrid-Vlasov simulation of soft X-ray emissions at the Earth’s dayside magnetospheric boundaries

Solar wind charge exchange produces emissions in the soft X-ray energy range which can enable the study of near-Earth space regions such as the magnetopause,the magnetosheath and the polar cusps by remote sensing techniques.The Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)and Lunar Environment heliospheric X-ray Imager(LEXI)missions aim to obtain soft Xray images of near-Earth space thanks to their Soft X-ray Imager(SXI)instruments.While earlier modeling works have already simulated soft X-ray images as might be obtained by SMILE SXI during its mission,the numerical models used so far are all based on the magnetohydrodynamics description of the space plasma.To investigate the possible signatures of ion-kinetic-scale processes in soft Xray images,we use for the first time a global hybrid-Vlasov simulation of the geospace from the Vlasiator model.The simulation is driven by fast and tenuous solar wind conditions and purely southward interplanetary magnetic field.We first produce global X-ray images of the dayside near-Earth space by placing a virtual imaging satellite at two different locations,providing meridional and equatorial views.We then analyze regional features present in the images and show that they correspond to signatures in soft X-ray emissions of mirrormode wave structures in the magnetosheath and flux transfer events(FTEs)at the magnetopause.Our results suggest that,although the time scales associated with the motion of those transient phenomena will likely be significantly smaller than the integration time of the SMILE and LEXI imagers,mirror-mode structures and FTEs can cumulatively produce detectable signatures in the soft X-ray images.For instance,a local increase by 30%in the proton density at the dayside magnetopause resulting from the transit of multiple FTEs leads to a 12%enhancement in the line-of-sight-and time-integrated soft X-ray emissivity originating from this region.Likewise,a proton density increase by 14%in the magnetosheath associated with mirror-mode structures can result in an enhancement in the soft X-ray signal by 4%.These are likely conservative estimates,given that the solar wind conditions used in the Vlasiator run can be expected to generate weaker soft X-ray emissions than the more common denser solar wind.These results will contribute to the preparatory work for the SMILE and LEXI missions by providing the community with quantitative estimates of the effects of small-scale,transient phenomena occurring on the dayside.

Daily rolling estimation of carbon emission cost of coal-fired units considering long-cycle interactive operation simulation of carbon-electricity market

The high overlap of participants in the carbon emissions trading and electricity markets couples the operations of the two markets.The carbon emission cost(CEC)of coal-fired units becomes part of the power generation cost through market coupling.The accuracy of CEC calculation affects the clearing capacity of coal-fired units in the electric power market.Study of carbon–electricity market interaction and CEC calculations is still in its initial stages.This study analyzes the impact of carbon emissions trading and compliance on the operation of the electric power market and defines the cost transmission mode between the carbon emissions trading and electric power markets.A long-period interactive operation simulation mechanism for the carbon–electricity market is established,and operation and trading models of the carbon emissions trading market and electric power market are established.A daily rolling estimation method for the CEC of coal-fired units is proposed,along with the CEC per unit electric quantity of the coal-fired units.The feasibility and effectiveness of the proposed method are verified through an example simulation,and the factors influencing the CEC are analyzed.

A laboratory acoustic emission experiment and numerical simulation of rock fracture driven by a high-pressure fluid source

In order to improve our understanding of rock fracture and fault instability driven by high-pressure fluid sources, the authors carried out rock fracture tests using granite under a confining pressure of 80 MPa with fluid injection in the laboratory. Furthermore, we tested a number of numerical models using the FLAC;modeling software to find the best model to represent the experimental results. The high-speed multichannel acoustic emission（AE） waveform recording system used in this study made it possible to examine the total fracture process through detailed monitoring of AE hypocenters and seismic velocity.The experimental results show that injecting high-pressure oil into the rock sample can induce AE activity at very low stress levels and can dramatically reduce the strength of the rock. The results of the numerical simulations show that major experimental results, including the strength, the temporal and spatial patterns of the AE events, and the role of the fluid can be represented fairly well by a model involving（1） randomly distributed defect elements to model pre-existing cracks,（2） random modification of rock properties to represent inhomogeneity introduced by different mineral grains, and（3）macroscopic inhomogeneity. Our study, which incorporates laboratory experiments and numerical simulations, indicates that such an approach is helpful in finding a better model not only for simulating experimental results but also for upscaling purposes.

Recent Advances in Computational Simulation of Macro-,Meso-,and Micro-Scale Biomimetics Related Fluid Flow Problems

Over the last decade, computational methods have been intensively applied to a variety of scientific researches and engineering designs. Although the computational fluid dynamics （CFD） method has played a dominant role in studying and simulating transport phenomena involving fluid flow and heat and mass transfers, in recent years, other numerical methods for the simulations at meso- and micro-scales have also been actively applied to solve the physics of complex flow and fluid-interface interactions. This paper presents a review of recent advances in multi-scale computational simulation of biomimetics related fluid flow problems. The state-of-the-art numerical techniques, such as lattice Boltzmann method （LBM）, molecular dynamics （MD）, and conventional CFD, applied to different problems such as fish flow, electro-osmosis effect of earthworm motion, and self-cleaning hydrophobic surface, and the numerical approaches are introduced. The new challenging of modelling biomimetics problems in developing the physical conditions of self-clean hydrophobic surfaces is discussed.

Simulation and optimization of an industrial gas condensate stabilization unit to modify LPG and NGL production with minimizing CO2 emission to the environment

In the present study, a great effort was made to improve the performance of an industrial liquefied petroleum gas(LPG) and natural gas liquid(NGL) production unit in one of the major gas refinery located at Pars special economic zone in Iran. To demonstrate and obtain the optimal condition, the unit was simulated by using a steady-state flowsheet simulator, i.e. Aspen Plus, under different operational conditions. According to the simulation results,the unit was not operational under its optimal conditions due to some defects in the cooling system at top stage of the debutanizer tower(DBT) during hot and humid seasons. Additionally, the vapor pressure of produced LPG and accordingly the amount of its flaring were decreased by reducing the temperature of debutanizer tower at top stages. In the optimization section, the DBT condenser and reboiler heat duty, temperature, and pressure were regulated as adjustable parameters. The simulation results demonstrated that by applying the optimum suggestion in the hot months, the reflux stream temperature was reached about 55 ℃ which caused an efficient increment in LPG production(about 4%) with adjusting the propane component in LPG, based on the standard range as the plant criteria. Moreover, after applying modifications, about 750 t of LPG product was saved from flaring during five hot months of the year, which resulted in 360000 USD extra annual income for the company.Finally, from environmental point of view, this optimization caused to reduce 81 t of CO_2 emission to the environment. Therefore, the current investigation must be introduced as a friendly environmentally process.

Measurement and Scenario Simulation of Effect of Urbanisation on Regional CO_2 Emissions Based on UEC-SD Model:A Case Study in Liaoning Province,China

Based on the logical causal relationship and taking Liaoning Province, China, which is the Chinese traditional industrial base and is in the stage of accelerated urbanisation, as a case study, this study builds the ＇Urbanisation-Energy Consumption-COn Emissions System Dynamics （UEC-SD）＇ model using a system dynamics method. The UEC-SD model is applied to analyse the effect of the ar- banisation process on the regional energy structure and CO2 emissions, followed by simulation of future production and living energy consumption structure as well as the evolutionary trend of CO2 emissions of three urbanisation scenarios （low speed, intermediate speed and high speed） under the assumed boundary conditions in urban and rural areas of Liaoning Province, China. The results show that the urbanisation process can alter production and the living energy consumption structure and thereby change regional CO2 emissions. An increase in the urbanisation rate in case area will lead to regional COz emissions rising in the short term, but when the urbanisation rate approaches 80%, CO2 emissions will reach a peak value and then decrease. Comparison of different urbanisation rates showed that pro- duction and living energy consumption exhibit different directions of change and rules in urban and rural areas. The effect of urbanisa- tion on CO2 emissions and energy structure is not direct, and urbanisation can increase the differences in energy and CO2 emissions between urban and rural areas caused by the industrial structure, technical level and other factors.

Characterization of Nitrogen Glow Discharge Plasma via Optical Emission Spectrum Simulation

Optical emission spectroscopy in nitrogen glow discharge plasma is simulated, and the collision excitations and characteristic emissions of the species （N2, N2^＋, N^＋, N） are investigated by a Monte Carlo model for nitrogen molecular gas discharge. The excitation rates of the main excited states are calculated and the corresponding relation and relative magnitude between the distribution of excitation rate of a certain excited state and the distributions of the emission rates of various lines originating from this excited level are also explored. The simulated results are compared with the experimental measurements in two typical discharge conditions. The luminescence mechanism of the line N2^＋： 391.4 nm is explained based on the microscopic plasma processes. The cathode glow in N2 discharge is found to be mainly caused by N^＋ impact excitation and the intensity of cathode glow decreases with the voltage. The corresponding relation between the emission rate or intensity of the 391.4 nm line and the production rate and the density of N2^＋ is also examined.

Molecular Dynamics Simulation and Experimental Proof of Hydrogen-enhanced Dislocation Emission in Nickel

A quasi three dimensions molecular dynamic method was used to simulate the effect of hydrogen on dislocation emission and crack propagation in nickel. In situ observation in a transmission electron microscope (TEM) was used to confirm the simulation results. The simulation result indicated that hydrogen solubilized in nickel decreased the critical stress intensity for the dislocation emission, i.e., hydrogen enhanced dislocation emission. In situ observation in TEM showed that hydrogen enhanced dislocation emission and motion before the initiation of hydrogen-induced crack.

Diagnostic of capacitively coupled radio frequency plasma from electrical discharge characteristics：comparison with optical emission spectroscopy and fluid model simulation

The capacitively coupled radio frequency（CCRF）plasma has been widely used in various fields.In some cases,it requires us to estimate the range of key plasma parameters simpler and quicker in order to understand the behavior in plasma.In this paper,a glass vacuum chamber and a pair of plate electrodes were designed and fabricated,using 13.56 MHz radio frequency（RF）discharge technology to ionize the working gas of Ar.This discharge was mathematically described with equivalent circuit model.The discharge voltage and current of the plasma were measured atdifferent pressures and different powers.Based on the capacitively coupled homogeneous discharge model,the equivalent circuit and the analytical formula were established.The plasma density and temperature were calculated by using the equivalent impedance principle and energy balance equation.The experimental results show that when RF discharge power is 50–300 W and pressure is 25–250 Pa,the average electron temperature is about 1.7–2.1 e V and the average electron density is about 0.5？×10^17–3.6？×10^17m^-3.Agreement was found when the results were compared to those given by optical emission spectroscopy and COMSOL simulation.

Simulation of temporal and spatial change of N_2O emissions in the Yangtze River Delta

A biogeochemical model(DNDC) is combined with a plant ecological model to estimate N_2O emission from rice paddy fields in the Yangtze River Delta region. The model is driven by local meteorological, soil, and physiological data and is validated for 1999 and 2000 at a site in the region, which showed that the simulated N_2O emissions agree fairly well with the observed data. This adds some confidence in the estimated N_2O emissions during 1950 and 2000 in the Hangzhou Region. A significant correlation between the N_2O emissions and the population for the Hangzhou Region is found, which is due to a combination of increased application of fertilizers and cultivated area. Such a correlation can not be established for the whole Yangtze River Delta region when the data of both urban and rural areas are included. However, when the data from the heavily urbanized areas are excluded, a significant correlation between population and N_2O emissions emerges. The results show clearly that both the temporal and the spatial N_2O emissions have significant positive relationship with population under traditional farming practice. These results have implications for suitable mitigation options towards a sustainable agriculture and environment in this region.

Micro-Scale Motion Precision Simulation Method for a New-Type 6-DOF Micro-Manipulation Robot

A new 6-DOF micro-manipulation robot based on 3-PPTTRS parallel mechanisms in combination with flexure hinges is proposed. The design principle of the mechanism is introduced, and the kinematics analysis method based on differentiation is used to get the (inverse) kinematics equations. Then a micro-scale motion precision simulation method is proposed according to finite element analysis (FEA), and the prediction of robot’s motion precision in design phase is realized. The simulation result indicates that the 6-DOF micro-manipulation robot can meet the design specification.

Numerical Simulation of Cold-Start Emission for the Three-Way Catalytic Converter: Mathematical Model and Result Analysis

This paper integrated a two-dimensional axisymmetrical transient model applicable to cold-start emission applications. The model can be used to simulate and explain effects of the flow and temperature distribution on performance of a converter. The evolutions of distribution of the temperature and concentration in the monolith during the cold-start period and the effects of flow distribution in the monolith on the cold-start performance are simulated in terms of the integrated model. The investigation indicates that the axial and radial gradients of temperature of the solid become steeper as the inlet gas temperature ramp increases; this furthermore results in the movement of reaction region in the monolith, and the flow distribution in the monolith affects the radial distribution of temperature of the solid;the radial gradients of temperature of the solid become greater as the flow uniformity index decreases, whereas the light-off time doesn't always increase as the flow uniformity index decreases. The analyses on the distribution of temperature and concentration in the monolith show that the catalytic reaction zone concentrates in central area near the front face. The predicted curves of the velocity distribution have a good agreement with the experimental data.

Acoustic emission-based numerical simulation of tectonic stress field for tectoclase prediction in shale reservoirs of the northern Guizhou area, China

Natural fractures,like tectoclases,are essential in the formation of shale gas reservoirs and have been the focus of study for shale gas development.Tectoclases provide most storage space for gas and are largely controlled by the paleo-tectonic stress field in shale reservoirs of the Niutitang Formation,northern Guizhou area,China.An accurate prediction of the development and distribution of tectoclases in the reservoirs is of great significance to exploring and developing shale gas sweet spots in the area.Based on geological structure evolution and fracture characterization,this study is focused on factors that control the fracture development in the Niutitang Formation shale reservoirs in northern Guizhou through characterization and modeling of geomechanisms and tectonic movements.A geomechanical model is formulated for the shale reservoirs against the geological background of the area.On this basis,the fractures are predicted by using the acoustic emission data.Numerical simulation results show that the development and distribution of tectoclase is controlled by fault zones,some of which have no obvious turning points with tectoclase in the middle sections being more developed and fragmented than those at the two ends.Some of these have obvious S-shaped turning points where tectoclases are the most developed and fragmented.

Exploring the moderating role of financial development in environmental Kuznets curve for South Africa:fresh evidence from the novel dynamic ARDL simulations approach

The extant literature has produced mixed evidence on the relationship between finan-cial development and ecological sustainability.This work addresses this conundrum by investigating financial development’s direct and indirect consequences on ecologi-cal quality utilizing the environmental Kuznets curve(EKC)methodological approach.Our empirical analysis is based on the novel dynamic autoregressive distributed lag simulations approach for South Africa between 1960 and 2020.The results,which used five distinct financial development measures,demonstrate that financial develop-ment boosts ecological integrity and environmental sustainability over the long and short terms.In the instance of South Africa,we additionally confirm the validity of the EKC theory.More importantly,the outcomes of the indirect channels demonstrate that financial development increases energy usage’s role in causing pollution while attenuating the detrimental impacts of economic growth,trade openness,and foreign direct investment on ecological quality.Moreover,the presence of an inadequate financial system is a requirement for the basis of the pollution haven hypothesis(PHH),which we examine using trade openness and foreign direct investment variables.PHH for both of these variables disappears when financial development crosses specified thresholds.Finally,industrial value addition destroys ecological quality while tech-nological innovation enhances it.This research provides some crucial policy recom-mendations and fresh perspectives for South Africa as it develops national initiatives to support ecological sustainability and reach its net zero emissions goal.

Revisiting the nexus between fiscal decentralization and CO_(2)emissions in South Africa:fresh policy insights

The argument over fiscal decentralization and carbon dioxide emission(CO_(2))reduction has received much attention.However,evidence to back this claim is limited.Economic theory predicts that fiscal decentralization affects environmental quality,but the specifics of this relationship are still up for debate.Some scholars noted that fiscal decentralization might lead to a race to the top,whereas others contended that it would result in a race to the bottom.In light of the current debates in environmental and development economics,this study aims to provide insight into how this relationship may function in South Africa from 1960 to 2020.In contrast to the existing research,the present study uses a novel dynamic autoregressive distributed lag simulation approach to assess the positive and negative changes in fiscal decentralization,scale effect,technique effect,technological innovation,foreign direct investment,energy consumption,industrial growth,and trade openness on CO_(2)emissions.The following are the main findings:(i)Fiscal decentralization had a CO_(2)emission reduction impact in the short and long run,highlighting the presence of the race to the top approach.(ii)Economic growth(as represented by the scale effect)eroded ecological integrity.However,its square(as expressed by technique effect)aided in strengthening ecological protection,validating the environmental Kuznets curve hypothesis.(iii)CO_(2)emissions were driven by energy utilization,trade openness,industrial value-added,and foreign direct investment,whereas technological innovation boosted ecological integrity.Findings suggest that further fiscal decentralization should be undertaken through further devolution of power to local entities,particularly regarding environmental policy issues,to maintain South Africa’s ecological sustainability.South Africa should also establish policies to improve environmental sustainability by strengthening a lower layer of government and clarifying responsibilities at the national and local levels to fulfill the energy-saving functions of fiscal expenditures.

Uncertainty in Dust Budget over East Asia Simulated by WRF/Chem with Six Different Dust Emission Schemes

In this study, the dependence of dust budgets on dust emission schemes is investigated through the simulation of dust storm events, which occurred during 14–25 March 2002, over East Asia, by the Weather Research and Forecasting with Chemistry(WRF/Chem) model coupled with six dust emission schemes. Generally, this model can reasonably reproduce the spatial distribution of surface dust concentration; however, the simulated total dust budget differs significantly with different emission schemes. Moreover, uncertainties in the simulated dust budget vary among regions. It is suggested that the dust emission scheme affects the regional dust budget directly through its impact on the total emitted dust amount; however, the inflow and outflow of dust aerosols simulated by different schemes within a region also depend on the geographical location of the dust emission region. Furthermore, the size distribution of dust particles for a specific dust emission scheme has proven to be important for dust budget calculation due to the dependence of dust deposition amount on dust size distribution.

Localization and Evaluation of Motor Vehicle Emission Simulator (MOVES) Model for Predicting the Emissions of Private Cars:a Case Study of Shenzhen City,China

Motor Vehicle emission simulator(MOVES)model was localized by changing the base emission rates in MySQL database of the model,and using the actual measured data for private cars in Shenzhen City,China.The performances of localized MOVES model and non-localized MOVES model were evaluated by comparing the predicted emission factors to the measured ones.The results showed that by localization of the base emission rates,the prediction accuracy of the localized MOVES model for hydrocarbon(HC)and nitrogen oxides(NO x)was significantly improved.The accuracy of the localized MOVES model simulations in the Opmode increased by 86%,88%and 71%for HC,76%,42%and 72%for NO x on arterial roads,expressways and highways.For carbon monoxide(CO),however,the simulation performance based on the average velocity mode on expressways and highways became poor after localization,with the decrease of 28%and 8%respectively.Overall,by the localization of the base emission rates,the relative errors of the simulated emission factors of HC,CO and NO x of private cars were less than 37%.

LARGE-EDDY SIMULATION OF TWO-PHASE REACTING FLOW IN MODEL COMBUSTOR

The gas-droplet two-phase reacting flow in a model combustor with the V-gutter flame holder is studied by an Eulerian-Lagrangian large-eddy simulation (LES) approach. The k-equation subgrid-scale model is used to simulate the subgrid eddy viscosity, and the eddy-break-up (EBU) combustion subgrid-scale model is used to determine the chemical reaction rate. A two-step turbulent combustion subgrid-scale model is employed for calculating carbon monoxide CO concentration, and the NO subgrid-scale pollutant formation model for the evaluation of the rate of NO formation. The heat flux model is applied to the prediction of radiant heat transfer. The gas phase is solved with the SIMPLE algorithm and a hybrid scheme in the staggered grid system. The liquid phase equations are solved in a Lagrangian frame in reference of the particle-source-in-cell (PSIC) algorithm. From simulation results, the exchange of mass, moment and energy between gas and particle fields for the reacting flow in the afterburner with a V-gutter flame holder can be obtained. By the comparison of experimental and simulation results, profile temperature and pollutant of the outlet are quite in agreement with experimental data. Results show that the LES approach for predicting the two-phase instantaneous reacting flow and pollutant emissions in the afterburner is feasible.

Effect of heterogeneity on mechanical and acoustic emission characteristics of rock specimen

The influence of heterogeneity on mechanical and acoustic emission characteristics of rock specimen under uniaxial compress was studied with numerical simulation methods.Weibull distribution function was adopted to describe the mesoscopic heterogeneity of rocks.The failure process of heterogeneous rock specimen under uniaxial loading was simulated using FLAC 3D software.Five schemes were adopted to investigate the influence of heterogeneity.The results demonstrate that as the homogeneity increases,the peak strength and brittleness of rocks increase,and the macro elastic modulus improves as well.Heterogeneity has great influence on macro elastic modulus and strength when the homogeneity coefficient is less than 20.0.The volume expansion is not so obvious when the homogeneity increases.As the homogeneity coefficient increases the acoustic emissions modes change from swarm shock to main shock.When the homogeneity coefficient is high,the cumulative acoustic emission events-axial strain curve is gentle before the rock failure.The numerical results agree with the previously numerical results and earlier experimental measurements.