The fuel sulfur content in marine fuels has been regulated in Sulfur Emission Control Areas(SECAs) since January 2015. However, other fuel characteristics are also believed to have an impact on particle emissions, par...The fuel sulfur content in marine fuels has been regulated in Sulfur Emission Control Areas(SECAs) since January 2015. However, other fuel characteristics are also believed to have an impact on particle emissions, particularly on the number of particles emitted. This study investigates the impact of the content of aromatics in fuel. To achieve fuel blends with concentrations of aromatics similar to those found in marine fuel oils, i.e. 20%–30% by volume(%vol.), normal diesel oil(4%–5% vol. aromatics) is doped with a mixture of aromatics. Emission measurements are conducted in test-bed engine facilities and particle emissions over a wide size range are analyzed. Results show a decreased number of particles emitted(or not change) with an increase in the aromatic concentration in fuel. This is because there is a reduction in the cetane number of the fuel with an increased aromatic content, which effects the combustion process and results in decreased particle formation. However, when ignition improver is used to increase the cetane number, particle emissions remain at a lower level than for normal diesel oil; thereby emphasizing the presence of other factors in the formation of particles.展开更多
Time-periodic driving has been an effective tool in the field of nonequilibrium quantum dynamics,which enables precise control of the particle interactions.We investigate the collective emission of particles from a Bo...Time-periodic driving has been an effective tool in the field of nonequilibrium quantum dynamics,which enables precise control of the particle interactions.We investigate the collective emission of particles from a Bose-Einstein condensate in a one-dimensional lattice with periodic drives that are separate in modulation amplitudes and relative phases.In addition to the enhancement of particle emission,we find that amplitude imbalances lead to energy shift and band broadening,while typical relative phases may give rise to similar gaps.These results offer insights into the specific manipulations of nonequilibrium quantum systems with tone-varying drives.展开更多
This work studies the amount of gaseous and particle emissions and deposits on heat exchanger surfaces in a boiler firedwith commercially available pellets and with pellets primed with magnesium oxide and magnesium hy...This work studies the amount of gaseous and particle emissions and deposits on heat exchanger surfaces in a boiler firedwith commercially available pellets and with pellets primed with magnesium oxide and magnesium hydroxide.The combustionexperiments were performed on a residential boiler of 20 kW.Substrates placed in the heat exchanger was analysed with SEM-EDX-mapping to evaluate the chemical composition of the deposits.The results show that particle emissions(PM 2.5)using the additivesincreased by about 50%and the mass of the deposits in the flue gas heat exchanger(excluding loose fly ash)increased by about25%compared to the combustion of pellets without additives.The amount of additives was found to be eight times higher than theamount of the main alkali metals potassium(K)and sodium(Na)which leads to the assumption that the additives were overdosedand therefore caused the problems reported.The SEM analysis of the substrates placed in the flue gas heat exchanger indicate that thedeposits of sodium(Na),potassium(K),chlorine(Cl)and sulphur(S)decrease using the additives.If this was due to theexpected chemical reactions or due to the loose fly ash covering the substrates after the test,could not be determined in this study.展开更多
On 2012 March 7, the STEREO Ahead and Behind spacecraft, along with near-Earth spacecraft (e.g. SOHO, Wind) situated between the two STEREO spacecraft, observed an extremely large global solar energetic particle (...On 2012 March 7, the STEREO Ahead and Behind spacecraft, along with near-Earth spacecraft (e.g. SOHO, Wind) situated between the two STEREO spacecraft, observed an extremely large global solar energetic particle (SEP) event in Solar Cycle 24. Two successive coronal mass ejections (CMEs) have been detected close in time. From the multi-point in-situ observations, it can be found that this SEP event was caused by the first CME, but the second one was not involved. Using velocity dispersion analysis (VDA), we find that for a well magnetically connected point, the energetic protons and electrons are released nearly at the same time. The path lengths to STEREO-B (STB) for protons and electrons have a distinct difference and deviate remarkably from the nominal Parker spiral path length, which is likely due to the presence of interplanetary magnetic structures situated between the source and STB. Also, the VDA method seems to only obtain reasonable results at well-connected locations and the inferred release times of energetic particles in different energy channels are similar. We suggest that good-connection is crucial for obtaining both an accurate release time and path length simultaneously, agreeing with the modeling result of Wang & Qin (2015).展开更多
The results of measurements conducted to determine the number and mass concentration of particles emitted from the liquefied natural gas (LNG) fueled spark ignition engines are presented. Particle size distributions...The results of measurements conducted to determine the number and mass concentration of particles emitted from the liquefied natural gas (LNG) fueled spark ignition engines are presented. Particle size distributions were measured at different speeds, different loads and ESC cycles. The nanoparticles with diameter smaller than 39 nm, measured by the electrical low-pressure impactor (ELPI), are dominant in number con- centration that is nearly 92.7 % of the total number of the emitted particles at the peak point. As for the mass of emission particle, it is shown that the mass of the particles greater than 1.2μm is more than 65 % that of the emitted particles.展开更多
According to the solar proton data observed by Geostationary Operational Environmental Satellites (GOES), ground-based neutron monitors on Earth and near-relativistic electron data measured by the ACE spacecraft, th...According to the solar proton data observed by Geostationary Operational Environmental Satellites (GOES), ground-based neutron monitors on Earth and near-relativistic electron data measured by the ACE spacecraft, the onset times of protons with different energies and near-relativistic electrons have been estimated and compared with the time of solar soft and hard X-ray and radio burst data. The results show that first arriving relativistic and non-relativistic protons and electrons may have been accelerated by the concurrent flare. The results also suggest that release times of protons with different energies may be different, and the protons with lower energy may have been released earlier than those with higher energy. Some protons accelerated by concurrent flares may be further accelerated by the shock driven by the associated CME.展开更多
Number concentration and size distribution from gasoline ears are investigated at transient modes on the chassis dynamometers, which are measured using electrical low pressure impactor (ELPI) for the ECE15 and EUDC ...Number concentration and size distribution from gasoline ears are investigated at transient modes on the chassis dynamometers, which are measured using electrical low pressure impactor (ELPI) for the ECE15 and EUDC cycles. Results indicate that, during cold start, particle number emission is higher than that under hot start. It is found that the number of particles increases with the vehicle speeds. Furthermore, particles with diameter smaller than 200 nm constitute the predominant part of total emission in the entire cycle. In addition, the tentative information about composition of emitted particles is also discussed.展开更多
The electrical and optical effects of particles on the nano aluminum film deposited by thermal evaporation was investigated. From the characterization results of scanning electron microscope(SEM), the accumulation i...The electrical and optical effects of particles on the nano aluminum film deposited by thermal evaporation was investigated. From the characterization results of scanning electron microscope(SEM), the accumulation in tens of nanometers had been observed. The current-voltage(I-V) curve of the sample indicates its nonlinear electrical characters expecting the corresponding nonlinear optical properties. By the theoretical calculation, nonlinear conduction of the carrier transportation may result from the barrier-well-barrier structure, where negative resistance and Coulomb blockade effect appears. The simulation results are approximately matched with the experimental results. By testing the fluorescence emission spectrum of the sample, peaks were found to be located at 420 and 440 nm. In addition, the full width at half maximum(FWHM) had been obviously broadened by means of adding 2, 5-diphenyloxazole(DPO). Therefore, discrete energy levels could be estimated inside those particles.展开更多
Recently, S. W. Kahler studied the timescales of solar energetic particle (SEP) events asso- ciated with coronal mass ejections (CMEs) from analysis of spacecraft data. They obtained different timescales for SEP e...Recently, S. W. Kahler studied the timescales of solar energetic particle (SEP) events asso- ciated with coronal mass ejections (CMEs) from analysis of spacecraft data. They obtained different timescales for SEP events, such as TO, the onset time from CME launch to SEP onset, TR, the rise time from onset to half the peak intensity (0.5/p), and TD, the duration of the SEP intensity above 0.5Ip. In this work, we solve the transport equation for SEPs considering interplanetary coronal mass ejection (ICME) shocks as energetic particle sources. With our modeling assumptions, our simulations show similar results to Kahler's analysis of spacecraft data, that the weighted average of TD increases with both CME speed and width. Moreover, from our simulation results, we suggest TD is directly dependent on CME speed, but not dependent on CME width, which were not found in the analysis of observational data.展开更多
On 2017 September 10,a fast coronal mass ejection(CME)erupted from the active region(AR)12673,leading to a ground level enhancement(GLE)event at Earth.Using the 2D improved Particle Acceleration and Transport in the H...On 2017 September 10,a fast coronal mass ejection(CME)erupted from the active region(AR)12673,leading to a ground level enhancement(GLE)event at Earth.Using the 2D improved Particle Acceleration and Transport in the Heliosphere(iPATH)model,we model the large solar energetic particle(SEP)event of 2017 September 10 observed at Earth,Mars and STEREO-A.Based on observational evidence,we assume that the CME-driven shock experienced a large lateral expansion shortly after the eruption,which is modeled by a double Gaussian velocity profile in this simulation.We apply the in-situ shock arrival times and the observed CME speeds at multiple spacecraft near Earth and Mars as constraints to adjust the input model parameters.The modeled time intensity profiles and fluence for energetic protons are then compared with observations.Reasonable agreements with observations at Mars and STEREO-A are found.The simulated results at Earth differ from observations of GOES-15.However,the simulated results at a heliocentric longitude 20°west to Earth fit reasonably well with the GOES observation.This can be explained if the pre-event solar wind magnetic field at Earth is not described by a nominal Parker field.Our results suggest that a large lateral expansion of the CME-driven shock and a distorted interplanetary magnetic field due to previous events can be important in understanding this GLE event.展开更多
Since many industrial applications rely on the processing of densely packed and moving granular ma-terial,obtaining bulk internal information on the particle movement inside the reactors is of great importance.Such in...Since many industrial applications rely on the processing of densely packed and moving granular ma-terial,obtaining bulk internal information on the particle movement inside the reactors is of great importance.Such information can be delivered by Positron Emission Particle Tracking(PEPT).By marking pellets with a positron-emitting radioisotope,the position of these tracer particles can be determined via the time-of-flight differences of the emitted gamma-ray pairs.The current paper proposes a PET-like detector system based on cost-effective organic plastic scintillators instead of the more common but expensive inorganic scintillators.This system is currently under construction and was tested for its resolution and efficiency in this simulation study.Using Monte Carlo simulations and the software toolkit Geant4,three different geometries(an empty glass box,a generic grate system,and a cubic box of 1 m3 completely filled with pellets)were investigated,leading to a spatial resolution in the millimeter range and an efficiency,defined as the ratio of reconstructed decay locations to simulated decays,of 2.7%,1.4%,and 0.3%.展开更多
This work is the second part of a simulation study investigating the processing of densely packed and moving granular assemblies by positron emission particle tracking (PEPT).Since medical positron emission tomography...This work is the second part of a simulation study investigating the processing of densely packed and moving granular assemblies by positron emission particle tracking (PEPT).Since medical positron emission tomography (PET) scanners commonly used for PEPT are very expensive,a PET-like detector system based on cost-effective organic plastic scintillator bars is being developed and tested for its capabilities.In this context,the spatial resolution of a resting positron source,a source moving on a freely designed model path,and a particle motion given by a discrete element method (DEM) simulation is studied using Monte Carlo simulations and the software toolkit Geant4.This not only extended the simulation and reconstruction to a moving source but also significantly improved the spatial resolution compared to previous work by adding oversampling and iteration to the reconstruction algorithm.Furthermore,in the case of a source following a trajectory developed from DEM simulations,a very good resolution of about 1 mm in all three directions and an average 3D deviation between simulated and reconstructed events of 2.3 mm could be determined.Thus,the resolution for realistic particle motion within the generic grate system (which is the test rig for further experimental studies) is well below the smallest particle size.The simulation of the dependence of the reconstruction accuracy on tracer particle location revealed a nearly constant efficiency within the entire detector system,which demonstrates that boundary effects can be neglected.展开更多
The issue of the influence of coronal holes (CHs) on coronal mass ejections (CMEs) in causing solar energetic particle (SEP) events is revisited. It is a continuation and extension of our previous work, in which...The issue of the influence of coronal holes (CHs) on coronal mass ejections (CMEs) in causing solar energetic particle (SEP) events is revisited. It is a continuation and extension of our previous work, in which no evident effects of CHs on CMEs in generating SEPs were found by statistically investigating 56 CME events. This result is consistent with the conclusion obtained by Kahler in 2004. We extrapolate the coronal magnetic field, define CHs as the regions consisting of only open magnetic field lines and perform a similar analysis on this issue for 76 events in total by extending the study interval to the end of 2008. Three key parameters, CH proximity, CH area and CH relative position, are involved in the analysis. The new result confirms the previous conclusion that CHs did not show any evident effect on CMEs in causing SEP events.展开更多
Solar type III radio bursts are an important diagnostic tool in the understanding of solar accelerated electron beams. They are a signature of propagating beams of nonthermal electrons in the solar atmosphere and the ...Solar type III radio bursts are an important diagnostic tool in the understanding of solar accelerated electron beams. They are a signature of propagating beams of nonthermal electrons in the solar atmosphere and the solar system. Consequently, they provide information on electron acceleration and transport, and the conditions of the background ambient plasma they travel through. We review the observational properties of type III bursts with an emphasis on recent results and how each property can help identify attributes of electron beams and the ambient background plasma. We also review some of the theoretical aspects of type III radio bursts and cover a number of numerical efforts that simulate electron beam transport through the solar corona and the heliosphere.展开更多
To investigate the dependence of large gradual solar energetic particle(SEP) events on the associated flares and coronal mass ejections(CMEs), the correlation coefficients(CCs) between peak intensities of E 〉 1...To investigate the dependence of large gradual solar energetic particle(SEP) events on the associated flares and coronal mass ejections(CMEs), the correlation coefficients(CCs) between peak intensities of E 〉 10 MeV(I10), E 〉 30 MeV(I30) and E 〉 50 MeV(I50) protons and soft X-ray(SXR) emission of associated flares and the speeds of associated CMEs in the three longitudinal areas W0–W39, W40–W70(hereafter the well connected region) and W71–W90 have been calculated.Classical correlation analysis shows that CCs between SXR emission and peak intensities of SEP events always reach their largest value in the well connected region and then decline dramatically in the longitudinal area outside the well connected region, suggesting that they may contribute to the production of SEPs in large SEP events. Both classical and partial correlation analyses show that SXR fluence is a better parameter describing the relationship between flares and SEP events. For large SEP events with source location in the well connected region, the CCs between SXR fluence and I10, I30 and I50 are0.58±0.12, 0.80±0.06 and 0.83±0.06 respectively, while the CCs between CME speed and I10, I30 and I50 are 0.56±0.12, 0.52±0.13 and 0.48±0.13 respectively. The partial correlation analyses show that in the well connected region, both CME shock and SXR fluence can significantly affect I10, but SXR peak flux makes no additional contribution. For E 〉 30 MeV protons with source location in the well connected region, only SXR fluence can significantly affect I30, and the CME shock makes a small contribution to I30, but SXR peak flux makes no additional contribution. For E 〉 50 MeV protons with source location in the well connected region, only SXR fluence can significantly affect I50, but both CME shock and SXR peak flux make no additional contribution. We conclude that these findings provide statistical evidence that for SEP events with source locations in the well connected region, a CME shock is only an effective accelerator for E 〈 30 MeV protons. However, flares are not only effective accelerators for E 〈 30 MeV protons, but also for E 〉 30 MeV protons, and E 〉 30 MeV protons may be mainly accelerated by concurrent flares.展开更多
To investigate the possible solar source of high-energy protons, correlation coefficients between the peak intensities of E ≥ 100 MeV protons, I100, and the peak flux and fluence of solar soft X-ray(SXR) emission, ...To investigate the possible solar source of high-energy protons, correlation coefficients between the peak intensities of E ≥ 100 MeV protons, I100, and the peak flux and fluence of solar soft X-ray(SXR) emission, and coronal mass ejection(CME) linear speed in the three longitudinal areas W0-W39, W40-W70 and W71-W90 have been calculated respectively. Classical correlation analysis shows that the correlation coefficients between CME speeds and I100 in the three longitudinal areas are0.28±0.21, 0.35±0.21 and 0.04±0.30 respectively. The classical correlation coefficients between I100 and SXR peak flux in the three longitudinal areas are 0.48±0.17, 0.72±0.13 and 0.02±0.30 respectively, while the correlation coefficients between I100 and SXR fluence in the three longitudinal areas are 0.25±0.21, 0.84±0.07 and 0.10±0.30 respectively. Partial correlation analysis shows that for solar proton events with source location in the well connected region(W40-W70), only SXR fluence can significantly affect the peak intensity of E ≥ 100 MeV protons, but SXR peak flux has little influence on the peak intensities of E ≥ 100 MeV protons; moreover, CME speed has no influence on the peak intensities of E ≥ 100 MeV protons. We conclude that these findings provide statistical evidence that E ≥ 100 MeV protons may be mainly accelerated by concurrent flares.展开更多
Data from the Solar Wind Ion Composition Spectrometer (SWICS) on Ulysses and synoptic maps from Kitt Peak are used to analyze the polar coronal holes of solar activity cycles 22 and 23 (from 1990 to end of 2003). ...Data from the Solar Wind Ion Composition Spectrometer (SWICS) on Ulysses and synoptic maps from Kitt Peak are used to analyze the polar coronal holes of solar activity cycles 22 and 23 (from 1990 to end of 2003). In the beginning of the declining phase of solar cycles 22 and 23, the north polar coronal holes (PCHs) appear about one year earlier than the ones in the south polar region. The solar wind velocity and the solar wind ionic charge composition exhibit a characteristic dependence on the solar wind source position within a PCH. From the center toward the boundary of a young PCH, the solar wind velocity decreases, coinciding with a shift of the ionic charge composition toward higher charge states. However, for an old PCH, the ionic charge composition does not show any obvious change, although the latitude evolution of the velocity is similar to that of a young PCH.展开更多
Major solar eruptions (flares, coronal mass ejections (CMEs) and solar energetic particles (SEPs)) strongly influence geospace and space weather. Currently, the mechanism of their influence on space weather is n...Major solar eruptions (flares, coronal mass ejections (CMEs) and solar energetic particles (SEPs)) strongly influence geospace and space weather. Currently, the mechanism of their influence on space weather is not well understood and requires a detailed study of the energetic relationship among these eruptive phenomena. From this perspective, we investigate 30 flares (observed by RHESSI), followed by weak to strong geomagnetic storms. Spectral analysis of these flares suggests a new power-law relationship (r - 0.79) between the hard X-ray (HXR) spectral index (before flarepeak) and linear speed of the associated CME observed by LASCO/SOHO. For 12 flares which were followed by SEP enhancement near Earth, HXR and SEP spectral analysis reveals a new scaling law (r - 0.9) between the hardest X-ray flare spectrum and the hardest SEP spectrum. Furthermore, a strong correlation is obtained between the linear speed of the CME and the hardest spectrum of the corresponding SEP event (r - 0.96). We propose that the potentially geoeffective flare and associated CME and SEP are well-connected through a possible feedback mechanism, and should be regarded within the framework of a solar eruption. Owing to their space weather effects, these new results will help improve our current understanding of the Sun-Earth relationship, which is a major goal of research programs in heliophysics.展开更多
The measurement of positions and sizes of radio sources in observations is important for un- derstanding of the flare evolution. For the first time, solar radio spectral fine structures in an M6.5 flare that occurred ...The measurement of positions and sizes of radio sources in observations is important for un- derstanding of the flare evolution. For the first time, solar radio spectral fine structures in an M6.5 flare that occurred on 2013 April 11 were observed simultaneously by several radio instruments at four different observatories: Chinese Solar Broadband Radio Spectrometer at Huairou (SBRS/Huairou), Ondrejov Radio Spectrograph in the Czech Republic (ORSC/Ondrejov), Badary Broadband Microwave Spectropolarimeter (BMS/Irkutsk), and spectrograph/IZMIRAN (Moscow, Troitsk). The fine structures included microwave zebra patterns (ZPs), fast pulsations and fiber bursts. They were observed during the flare brightening lo- cated at the tops of a loop arcade as shown in images taken by the extreme ultraviolet (EUV) telescope onboard NASA's satellite Solar Dynamics Observatory (SDO). The flare occurred at 06:58-07:26 UT in solar active region NOAA 11719 located close to the solar disk center. ZPs appeared near high frequency boundaries of the pulsations, and their spectra observed in Huairou and Ondrejov agreed with each other in terms of details. At the beginning of the flare's impulsive phase, a strong narrowband ZP burst occurred with a moderate left-handed circular polarization. Then a series of pulsations and ZPs were observed in almost unpolarized emission. After 07:00 UT a ZP appeared with a moderate right-handed polarization. In the flare decay phase (at about 07:25 UT), ZPs and fiber bursts become strongly right-hand polarized. BMS/Irkutsk spectral observations indicated that the background emission showed a left-handed circular polarization (similar to SBRS/Huairou spectra around 3 GHz). However, the fine structure appeared in the right-handed polarization. The dynamics of the polarization was associated with the motion of the flare ex- citer, which was observed in EUV images at 171 A and 131 A by the SDO Atmospheric Imaging Assembly (AIA). Combining magnetograms observed by the SDO Helioseismic and Magnetic Imager (HMI) with the homologous assumption of EUV flare brightenings and ZP bursts, we deduced that the observed ZPs correspond to the ordinary radio emission mode. However, future analysis needs to verify the assumption that zebra radio sources are really related to a closed magnetic loop, and are located at lower heights in the solar atmosphere than the source of pulsations.展开更多
The solar energetic particle(SEP)event is a kind of hazardous space weather phenomena,so its quantitative forecast is of great importance from the aspect of space environmental situation awareness.We present here a se...The solar energetic particle(SEP)event is a kind of hazardous space weather phenomena,so its quantitative forecast is of great importance from the aspect of space environmental situation awareness.We present here a set of SEP forecast tools,which consists of three components:(1)a simple polytropic solar wind model to estimate the background solar wind conditions at the inner boundary of 0.1 AU(about 20 R⊙);(2)an ice-cream-cone model to estimate the erupted coronal mass ejection(CME)parameters;and(3)the improved Particle Acceleration and Transport in the Heliosphere(i PATH)model to calculate particle fluxes and energy spectra.By utilizing the above models,we have simulated six realistic SEP events from 2010 August 14 to 2014 September 10,and compared the simulated results to the Geostationary Operational Environmental Satellites(GOES)spacecraft observations.The results show that the simulated fluxes of>10 Me V particles agree with the observations while the simulated fluxes of>100 Me V particles are higher than the observed data.One of the possible reasons is that we have adopted a simple method in the model to calculate the injection rate of energetic particles.Furthermore,we have conducted the ensemble numerical simulations over these events and investigated the effects of different background solar wind conditions at the inner boundary on SEP events.The results imply that the initial CME density plays an important role in determining the power spectrum,while the effect of varying background solar wind temperature is not significant.Naturally,we have examined the influence of CME initial density on the numerical prediction results for virtual SEP cases with different CME ejection speeds.The result shows that the effect of initial CME density variation is inversely associated with CME speed.展开更多
基金Angpanneföreningen’s Foundation for Research and Development(11-164)the Foundation for Swedish Environmental Research Institute(SIVL)Swedish Maritime Organization and Lighthouse for their financial support
文摘The fuel sulfur content in marine fuels has been regulated in Sulfur Emission Control Areas(SECAs) since January 2015. However, other fuel characteristics are also believed to have an impact on particle emissions, particularly on the number of particles emitted. This study investigates the impact of the content of aromatics in fuel. To achieve fuel blends with concentrations of aromatics similar to those found in marine fuel oils, i.e. 20%–30% by volume(%vol.), normal diesel oil(4%–5% vol. aromatics) is doped with a mixture of aromatics. Emission measurements are conducted in test-bed engine facilities and particle emissions over a wide size range are analyzed. Results show a decreased number of particles emitted(or not change) with an increase in the aromatic concentration in fuel. This is because there is a reduction in the cetane number of the fuel with an increased aromatic content, which effects the combustion process and results in decreased particle formation. However, when ignition improver is used to increase the cetane number, particle emissions remain at a lower level than for normal diesel oil; thereby emphasizing the presence of other factors in the formation of particles.
基金Project supported by the China Scholarship Council(Grant No.201906130092)the Natural Science Research Start-up Foundation of Recruiting Talents of Nanjing University of Posts and Telecommunications(Grant No.NY223065)the Natural Science Foundation of Sichuan Province(Grant No.2023NSFSC1330).
文摘Time-periodic driving has been an effective tool in the field of nonequilibrium quantum dynamics,which enables precise control of the particle interactions.We investigate the collective emission of particles from a Bose-Einstein condensate in a one-dimensional lattice with periodic drives that are separate in modulation amplitudes and relative phases.In addition to the enhancement of particle emission,we find that amplitude imbalances lead to energy shift and band broadening,while typical relative phases may give rise to similar gaps.These results offer insights into the specific manipulations of nonequilibrium quantum systems with tone-varying drives.
基金performed within the project SWX-Energi and financed by the European UnionRegion Dalarna+1 种基金Region Gvleborgand Dalarna University
文摘This work studies the amount of gaseous and particle emissions and deposits on heat exchanger surfaces in a boiler firedwith commercially available pellets and with pellets primed with magnesium oxide and magnesium hydroxide.The combustionexperiments were performed on a residential boiler of 20 kW.Substrates placed in the heat exchanger was analysed with SEM-EDX-mapping to evaluate the chemical composition of the deposits.The results show that particle emissions(PM 2.5)using the additivesincreased by about 50%and the mass of the deposits in the flue gas heat exchanger(excluding loose fly ash)increased by about25%compared to the combustion of pellets without additives.The amount of additives was found to be eight times higher than theamount of the main alkali metals potassium(K)and sodium(Na)which leads to the assumption that the additives were overdosedand therefore caused the problems reported.The SEM analysis of the substrates placed in the flue gas heat exchanger indicate that thedeposits of sodium(Na),potassium(K),chlorine(Cl)and sulphur(S)decrease using the additives.If this was due to theexpected chemical reactions or due to the loose fly ash covering the substrates after the test,could not be determined in this study.
基金supported at NUIST by the National Natural Science Foundation of China(NSFC)-41304150 for Ding L.G.at CMA by NSFC-41274193 and 41474166 for Le G.M
文摘On 2012 March 7, the STEREO Ahead and Behind spacecraft, along with near-Earth spacecraft (e.g. SOHO, Wind) situated between the two STEREO spacecraft, observed an extremely large global solar energetic particle (SEP) event in Solar Cycle 24. Two successive coronal mass ejections (CMEs) have been detected close in time. From the multi-point in-situ observations, it can be found that this SEP event was caused by the first CME, but the second one was not involved. Using velocity dispersion analysis (VDA), we find that for a well magnetically connected point, the energetic protons and electrons are released nearly at the same time. The path lengths to STEREO-B (STB) for protons and electrons have a distinct difference and deviate remarkably from the nominal Parker spiral path length, which is likely due to the presence of interplanetary magnetic structures situated between the source and STB. Also, the VDA method seems to only obtain reasonable results at well-connected locations and the inferred release times of energetic particles in different energy channels are similar. We suggest that good-connection is crucial for obtaining both an accurate release time and path length simultaneously, agreeing with the modeling result of Wang & Qin (2015).
文摘The results of measurements conducted to determine the number and mass concentration of particles emitted from the liquefied natural gas (LNG) fueled spark ignition engines are presented. Particle size distributions were measured at different speeds, different loads and ESC cycles. The nanoparticles with diameter smaller than 39 nm, measured by the electrical low-pressure impactor (ELPI), are dominant in number con- centration that is nearly 92.7 % of the total number of the emitted particles at the peak point. As for the mass of emission particle, it is shown that the mass of the particles greater than 1.2μm is more than 65 % that of the emitted particles.
基金funded by the National Natural Science Foundation of China(Grant Nos.41674166,41074132,41274193 and 41304144)the National Standard Research Program(Grant 200710123)
文摘According to the solar proton data observed by Geostationary Operational Environmental Satellites (GOES), ground-based neutron monitors on Earth and near-relativistic electron data measured by the ACE spacecraft, the onset times of protons with different energies and near-relativistic electrons have been estimated and compared with the time of solar soft and hard X-ray and radio burst data. The results show that first arriving relativistic and non-relativistic protons and electrons may have been accelerated by the concurrent flare. The results also suggest that release times of protons with different energies may be different, and the protons with lower energy may have been released earlier than those with higher energy. Some protons accelerated by concurrent flares may be further accelerated by the shock driven by the associated CME.
文摘Number concentration and size distribution from gasoline ears are investigated at transient modes on the chassis dynamometers, which are measured using electrical low pressure impactor (ELPI) for the ECE15 and EUDC cycles. Results indicate that, during cold start, particle number emission is higher than that under hot start. It is found that the number of particles increases with the vehicle speeds. Furthermore, particles with diameter smaller than 200 nm constitute the predominant part of total emission in the entire cycle. In addition, the tentative information about composition of emitted particles is also discussed.
基金Supported by the 973 Program(No.2014CB932103)the 863 Program(No.2013AA032501)the National Natural Science Foundation of China(NSFC No.21676015)
文摘The electrical and optical effects of particles on the nano aluminum film deposited by thermal evaporation was investigated. From the characterization results of scanning electron microscope(SEM), the accumulation in tens of nanometers had been observed. The current-voltage(I-V) curve of the sample indicates its nonlinear electrical characters expecting the corresponding nonlinear optical properties. By the theoretical calculation, nonlinear conduction of the carrier transportation may result from the barrier-well-barrier structure, where negative resistance and Coulomb blockade effect appears. The simulation results are approximately matched with the experimental results. By testing the fluorescence emission spectrum of the sample, peaks were found to be located at 420 and 440 nm. In addition, the full width at half maximum(FWHM) had been obviously broadened by means of adding 2, 5-diphenyloxazole(DPO). Therefore, discrete energy levels could be estimated inside those particles.
基金partly supported by the National Natural Science Foundation of China(Grant Nos.41304135,41574172,41374177 and 41125016)the CMA(Grant GYHY201106011)the Specialized Research Fund for State Key Laboratories of China
文摘Recently, S. W. Kahler studied the timescales of solar energetic particle (SEP) events asso- ciated with coronal mass ejections (CMEs) from analysis of spacecraft data. They obtained different timescales for SEP events, such as TO, the onset time from CME launch to SEP onset, TR, the rise time from onset to half the peak intensity (0.5/p), and TD, the duration of the SEP intensity above 0.5Ip. In this work, we solve the transport equation for SEPs considering interplanetary coronal mass ejection (ICME) shocks as energetic particle sources. With our modeling assumptions, our simulations show similar results to Kahler's analysis of spacecraft data, that the weighted average of TD increases with both CME speed and width. Moreover, from our simulation results, we suggest TD is directly dependent on CME speed, but not dependent on CME width, which were not found in the analysis of observational data.
基金NASA grants NNX17AI17G,80NSSC19K0075 and 80NSSC19K0629。
文摘On 2017 September 10,a fast coronal mass ejection(CME)erupted from the active region(AR)12673,leading to a ground level enhancement(GLE)event at Earth.Using the 2D improved Particle Acceleration and Transport in the Heliosphere(iPATH)model,we model the large solar energetic particle(SEP)event of 2017 September 10 observed at Earth,Mars and STEREO-A.Based on observational evidence,we assume that the CME-driven shock experienced a large lateral expansion shortly after the eruption,which is modeled by a double Gaussian velocity profile in this simulation.We apply the in-situ shock arrival times and the observed CME speeds at multiple spacecraft near Earth and Mars as constraints to adjust the input model parameters.The modeled time intensity profiles and fluence for energetic protons are then compared with observations.Reasonable agreements with observations at Mars and STEREO-A are found.The simulated results at Earth differ from observations of GOES-15.However,the simulated results at a heliocentric longitude 20°west to Earth fit reasonably well with the GOES observation.This can be explained if the pre-event solar wind magnetic field at Earth is not described by a nominal Parker field.Our results suggest that a large lateral expansion of the CME-driven shock and a distorted interplanetary magnetic field due to previous events can be important in understanding this GLE event.
基金funded by the DeutscheForschungsgemeinschaft(DFG,German Research Foundation)through 422037413-CRC/TRR 287"BULK-REACTION"。
文摘Since many industrial applications rely on the processing of densely packed and moving granular ma-terial,obtaining bulk internal information on the particle movement inside the reactors is of great importance.Such information can be delivered by Positron Emission Particle Tracking(PEPT).By marking pellets with a positron-emitting radioisotope,the position of these tracer particles can be determined via the time-of-flight differences of the emitted gamma-ray pairs.The current paper proposes a PET-like detector system based on cost-effective organic plastic scintillators instead of the more common but expensive inorganic scintillators.This system is currently under construction and was tested for its resolution and efficiency in this simulation study.Using Monte Carlo simulations and the software toolkit Geant4,three different geometries(an empty glass box,a generic grate system,and a cubic box of 1 m3 completely filled with pellets)were investigated,leading to a spatial resolution in the millimeter range and an efficiency,defined as the ratio of reconstructed decay locations to simulated decays,of 2.7%,1.4%,and 0.3%.
基金funded by the Deutsche Forschungsgemeinschaft (DFG,German Research Foundation)-Project-ID 422037413-TRR 287.
文摘This work is the second part of a simulation study investigating the processing of densely packed and moving granular assemblies by positron emission particle tracking (PEPT).Since medical positron emission tomography (PET) scanners commonly used for PEPT are very expensive,a PET-like detector system based on cost-effective organic plastic scintillator bars is being developed and tested for its capabilities.In this context,the spatial resolution of a resting positron source,a source moving on a freely designed model path,and a particle motion given by a discrete element method (DEM) simulation is studied using Monte Carlo simulations and the software toolkit Geant4.This not only extended the simulation and reconstruction to a moving source but also significantly improved the spatial resolution compared to previous work by adding oversampling and iteration to the reconstruction algorithm.Furthermore,in the case of a source following a trajectory developed from DEM simulations,a very good resolution of about 1 mm in all three directions and an average 3D deviation between simulated and reconstructed events of 2.3 mm could be determined.Thus,the resolution for realistic particle motion within the generic grate system (which is the test rig for further experimental studies) is well below the smallest particle size.The simulation of the dependence of the reconstruction accuracy on tracer particle location revealed a nearly constant efficiency within the entire detector system,which demonstrates that boundary effects can be neglected.
基金supported by grants from the National Natural Science Foundation of China(Grant Nos.40904046,40874075 and 40525014)the 973 National Basic Research Program(2006CB806304)+2 种基金the Ministry of Education of China(200530)the Program for New Century Excellent Talents in University(NCET-08-0524)the Chinese Academy of Sciences(KZCX2-YW-QN511, KJCX2-YW-N28 and the startup fund)
文摘The issue of the influence of coronal holes (CHs) on coronal mass ejections (CMEs) in causing solar energetic particle (SEP) events is revisited. It is a continuation and extension of our previous work, in which no evident effects of CHs on CMEs in generating SEPs were found by statistically investigating 56 CME events. This result is consistent with the conclusion obtained by Kahler in 2004. We extrapolate the coronal magnetic field, define CHs as the regions consisting of only open magnetic field lines and perform a similar analysis on this issue for 76 events in total by extending the study interval to the end of 2008. Three key parameters, CH proximity, CH area and CH relative position, are involved in the analysis. The new result confirms the previous conclusion that CHs did not show any evident effect on CMEs in causing SEP events.
基金supported by a SUPA Advanced Fellowship (Hamish Reid)the European Research Council under the SeismoSun Research Project No. 321141 (Heather Ratcliffe)the Marie Curie PIRSESGA- 2011-295272 RadioSun project
文摘Solar type III radio bursts are an important diagnostic tool in the understanding of solar accelerated electron beams. They are a signature of propagating beams of nonthermal electrons in the solar atmosphere and the solar system. Consequently, they provide information on electron acceleration and transport, and the conditions of the background ambient plasma they travel through. We review the observational properties of type III bursts with an emphasis on recent results and how each property can help identify attributes of electron beams and the ambient background plasma. We also review some of the theoretical aspects of type III radio bursts and cover a number of numerical efforts that simulate electron beam transport through the solar corona and the heliosphere.
基金funded by the National Basic Research Program of China (973 Program,Grants 2012CB957801 and 2014CB744203)the National Natural Science Foundation of China (Grant Nos.41074132,41274193,41474166,41304144,11303017 and 11533005)the National Standard Research Program (Grant 200710123)
文摘To investigate the dependence of large gradual solar energetic particle(SEP) events on the associated flares and coronal mass ejections(CMEs), the correlation coefficients(CCs) between peak intensities of E 〉 10 MeV(I10), E 〉 30 MeV(I30) and E 〉 50 MeV(I50) protons and soft X-ray(SXR) emission of associated flares and the speeds of associated CMEs in the three longitudinal areas W0–W39, W40–W70(hereafter the well connected region) and W71–W90 have been calculated.Classical correlation analysis shows that CCs between SXR emission and peak intensities of SEP events always reach their largest value in the well connected region and then decline dramatically in the longitudinal area outside the well connected region, suggesting that they may contribute to the production of SEPs in large SEP events. Both classical and partial correlation analyses show that SXR fluence is a better parameter describing the relationship between flares and SEP events. For large SEP events with source location in the well connected region, the CCs between SXR fluence and I10, I30 and I50 are0.58±0.12, 0.80±0.06 and 0.83±0.06 respectively, while the CCs between CME speed and I10, I30 and I50 are 0.56±0.12, 0.52±0.13 and 0.48±0.13 respectively. The partial correlation analyses show that in the well connected region, both CME shock and SXR fluence can significantly affect I10, but SXR peak flux makes no additional contribution. For E 〉 30 MeV protons with source location in the well connected region, only SXR fluence can significantly affect I30, and the CME shock makes a small contribution to I30, but SXR peak flux makes no additional contribution. For E 〉 50 MeV protons with source location in the well connected region, only SXR fluence can significantly affect I50, but both CME shock and SXR peak flux make no additional contribution. We conclude that these findings provide statistical evidence that for SEP events with source locations in the well connected region, a CME shock is only an effective accelerator for E 〈 30 MeV protons. However, flares are not only effective accelerators for E 〈 30 MeV protons, but also for E 〉 30 MeV protons, and E 〉 30 MeV protons may be mainly accelerated by concurrent flares.
基金jointly funded by the National Basic Research Program of China (973 Program, Grants 2012CB957801 and 2014CB744203)the National Natural Science Foundation of China (Grants 41074132, 41274193, 41474166, 41304144, 11303017 and 11533005)the National Standard Research Program (Grant 200710123)
文摘To investigate the possible solar source of high-energy protons, correlation coefficients between the peak intensities of E ≥ 100 MeV protons, I100, and the peak flux and fluence of solar soft X-ray(SXR) emission, and coronal mass ejection(CME) linear speed in the three longitudinal areas W0-W39, W40-W70 and W71-W90 have been calculated respectively. Classical correlation analysis shows that the correlation coefficients between CME speeds and I100 in the three longitudinal areas are0.28±0.21, 0.35±0.21 and 0.04±0.30 respectively. The classical correlation coefficients between I100 and SXR peak flux in the three longitudinal areas are 0.48±0.17, 0.72±0.13 and 0.02±0.30 respectively, while the correlation coefficients between I100 and SXR fluence in the three longitudinal areas are 0.25±0.21, 0.84±0.07 and 0.10±0.30 respectively. Partial correlation analysis shows that for solar proton events with source location in the well connected region(W40-W70), only SXR fluence can significantly affect the peak intensity of E ≥ 100 MeV protons, but SXR peak flux has little influence on the peak intensities of E ≥ 100 MeV protons; moreover, CME speed has no influence on the peak intensities of E ≥ 100 MeV protons. We conclude that these findings provide statistical evidence that E ≥ 100 MeV protons may be mainly accelerated by concurrent flares.
文摘Data from the Solar Wind Ion Composition Spectrometer (SWICS) on Ulysses and synoptic maps from Kitt Peak are used to analyze the polar coronal holes of solar activity cycles 22 and 23 (from 1990 to end of 2003). In the beginning of the declining phase of solar cycles 22 and 23, the north polar coronal holes (PCHs) appear about one year earlier than the ones in the south polar region. The solar wind velocity and the solar wind ionic charge composition exhibit a characteristic dependence on the solar wind source position within a PCH. From the center toward the boundary of a young PCH, the solar wind velocity decreases, coinciding with a shift of the ionic charge composition toward higher charge states. However, for an old PCH, the ionic charge composition does not show any obvious change, although the latitude evolution of the velocity is similar to that of a young PCH.
基金the CAWSES-India Program, supported by the Indian Space Research Organization (ISRO), Dept. of Space, Govt. of India
文摘Major solar eruptions (flares, coronal mass ejections (CMEs) and solar energetic particles (SEPs)) strongly influence geospace and space weather. Currently, the mechanism of their influence on space weather is not well understood and requires a detailed study of the energetic relationship among these eruptive phenomena. From this perspective, we investigate 30 flares (observed by RHESSI), followed by weak to strong geomagnetic storms. Spectral analysis of these flares suggests a new power-law relationship (r - 0.79) between the hard X-ray (HXR) spectral index (before flarepeak) and linear speed of the associated CME observed by LASCO/SOHO. For 12 flares which were followed by SEP enhancement near Earth, HXR and SEP spectral analysis reveals a new scaling law (r - 0.9) between the hardest X-ray flare spectrum and the hardest SEP spectrum. Furthermore, a strong correlation is obtained between the linear speed of the CME and the hardest spectrum of the corresponding SEP event (r - 0.96). We propose that the potentially geoeffective flare and associated CME and SEP are well-connected through a possible feedback mechanism, and should be regarded within the framework of a solar eruption. Owing to their space weather effects, these new results will help improve our current understanding of the Sun-Earth relationship, which is a major goal of research programs in heliophysics.
基金supported by the Chinese Academy of Sciences Visiting Professorship for Senior International Scientists(Grant No.2011T1J20)funded by Chinese Academy of Sciences President’s International Fellowship Initiative(Grant No.2015VMA014)+3 种基金supported by the Russian Foundation for Basic Research(Grants:13-02-00044,13-02-90472,14-02-91157 and 14-02-00367)the National Natural Science Foundation of China(Grant Nos.11273030,11103044,11103039,11221063,11373039 and 113111042)MOST(Grant2011CB811401)the National Major Scientific Equipment R&D Project(ZDYZ 2009-3 and P209/12/00103 GA CR)
文摘The measurement of positions and sizes of radio sources in observations is important for un- derstanding of the flare evolution. For the first time, solar radio spectral fine structures in an M6.5 flare that occurred on 2013 April 11 were observed simultaneously by several radio instruments at four different observatories: Chinese Solar Broadband Radio Spectrometer at Huairou (SBRS/Huairou), Ondrejov Radio Spectrograph in the Czech Republic (ORSC/Ondrejov), Badary Broadband Microwave Spectropolarimeter (BMS/Irkutsk), and spectrograph/IZMIRAN (Moscow, Troitsk). The fine structures included microwave zebra patterns (ZPs), fast pulsations and fiber bursts. They were observed during the flare brightening lo- cated at the tops of a loop arcade as shown in images taken by the extreme ultraviolet (EUV) telescope onboard NASA's satellite Solar Dynamics Observatory (SDO). The flare occurred at 06:58-07:26 UT in solar active region NOAA 11719 located close to the solar disk center. ZPs appeared near high frequency boundaries of the pulsations, and their spectra observed in Huairou and Ondrejov agreed with each other in terms of details. At the beginning of the flare's impulsive phase, a strong narrowband ZP burst occurred with a moderate left-handed circular polarization. Then a series of pulsations and ZPs were observed in almost unpolarized emission. After 07:00 UT a ZP appeared with a moderate right-handed polarization. In the flare decay phase (at about 07:25 UT), ZPs and fiber bursts become strongly right-hand polarized. BMS/Irkutsk spectral observations indicated that the background emission showed a left-handed circular polarization (similar to SBRS/Huairou spectra around 3 GHz). However, the fine structure appeared in the right-handed polarization. The dynamics of the polarization was associated with the motion of the flare ex- citer, which was observed in EUV images at 171 A and 131 A by the SDO Atmospheric Imaging Assembly (AIA). Combining magnetograms observed by the SDO Helioseismic and Magnetic Imager (HMI) with the homologous assumption of EUV flare brightenings and ZP bursts, we deduced that the observed ZPs correspond to the ordinary radio emission mode. However, future analysis needs to verify the assumption that zebra radio sources are really related to a closed magnetic loop, and are located at lower heights in the solar atmosphere than the source of pulsations.
基金supported by the National Science Foundation of China(No.42074224)the Key Research Program of the Chinese Academy of Sciences,grant No.ZDRE-KT-2021-3Pandeng Program of National Space Science Center,Chinese Academy of Sciences。
文摘The solar energetic particle(SEP)event is a kind of hazardous space weather phenomena,so its quantitative forecast is of great importance from the aspect of space environmental situation awareness.We present here a set of SEP forecast tools,which consists of three components:(1)a simple polytropic solar wind model to estimate the background solar wind conditions at the inner boundary of 0.1 AU(about 20 R⊙);(2)an ice-cream-cone model to estimate the erupted coronal mass ejection(CME)parameters;and(3)the improved Particle Acceleration and Transport in the Heliosphere(i PATH)model to calculate particle fluxes and energy spectra.By utilizing the above models,we have simulated six realistic SEP events from 2010 August 14 to 2014 September 10,and compared the simulated results to the Geostationary Operational Environmental Satellites(GOES)spacecraft observations.The results show that the simulated fluxes of>10 Me V particles agree with the observations while the simulated fluxes of>100 Me V particles are higher than the observed data.One of the possible reasons is that we have adopted a simple method in the model to calculate the injection rate of energetic particles.Furthermore,we have conducted the ensemble numerical simulations over these events and investigated the effects of different background solar wind conditions at the inner boundary on SEP events.The results imply that the initial CME density plays an important role in determining the power spectrum,while the effect of varying background solar wind temperature is not significant.Naturally,we have examined the influence of CME initial density on the numerical prediction results for virtual SEP cases with different CME ejection speeds.The result shows that the effect of initial CME density variation is inversely associated with CME speed.