This article presents the physics for determining an appropriate helicon plasma source for the linear experimental advanced device(LEAD)through tripartite mutual verification encompassing theoretical analysis,code sim...This article presents the physics for determining an appropriate helicon plasma source for the linear experimental advanced device(LEAD)through tripartite mutual verification encompassing theoretical analysis,code simulation,and experimental validation.Using the HELIC code,plasma excitation processes were simulated with three antenna configurations:m=1 half-helix,m=1 Boswell,and m=0 single-loop helicon antennas,and complemented by theoretical analysis.Key parameters including plasma impedance(R_(p))and energy deposition profiles along radial(P_(r))and axial(P_(z))directions were comparatively analyzed,revealing significantly enhanced R_(p),P_(r),and P_(z) values for the loop antenna configuration as compared with other configurations.Wave propagation equation solutions predicted a primary plasma generation layer at the antenna center;numerical simulations identified an additional plasma formation region at the antenna boundary,indicative of edge Landau damping effects.Interestingly,stronger axial magnetic fields do not necessarily result in higher plasma densities,especially for m=0 antenna configurations.Experimental validation conducted with an m=0 multi-loop plasma source confirmed these findings.Both theoretical analyses and experimental studies on large-volume plasma generation utilizing this innovative source elucidated the underlying mechanisms responsible for the remarkable low mode transition threshold of 150-watt input power and demonstrated significantly enhanced plasma confinement properties.展开更多
By utilization of different excitation power sources, linear plasma sources can be differentiated into DC, RF, VHF, microwave and dual frequency types. Through installing several linear plasma sources in parallel or a...By utilization of different excitation power sources, linear plasma sources can be differentiated into DC, RF, VHF, microwave and dual frequency types. Through installing several linear plasma sources in parallel or adopting the so-called roll-to-roll （air-to-air） process, scale uniform linear plasma sources were realized and successfully applied to the deposition of large area uniform dielectric thin films, Furthermore, the magnetic field system can effectively reduce the recombination losses on the wall of the vacuum chamber and enhance the plasma density. Linear plasma sources with approximately one square meter deposition area with the plasma density of 1011 cm 3 have been developed, some of which have been used for the deposition of dielectric layers and large area plasma etching.展开更多
The double pulse sources （DPS） method is presented for linear track estimation in this work. In the field of noise identification of underwater moving target, the Doppler will distort the frequency and amplitude of ...The double pulse sources （DPS） method is presented for linear track estimation in this work. In the field of noise identification of underwater moving target, the Doppler will distort the frequency and amplitude of the radiated noise. To eliminate this, the track estimation is necessary. In the DPS method, we first estimate bearings of two sinusoidal pulse sources installed in the moving target through baseline positioning method. Meanwhile, the emitted and recorded time of each pulse are also acquired. Then the linear track parameters will be achieved based on the geometry pattern with the help of double sources spacing. The simulated results confirm that the DPS improves the performance of the previous double source spacing method. The simulated experiments were carried out using a moving battery car to further evaluate its performance. When the target is 40-60m away, the experiment results show that biases of track azimuth and abeam distance of DPS are under 0.6° and 3.4m, respectively. And the average deviation of estimated velocity is around 0.25m/s.展开更多
High-dimensional data(a dataset with many features)were collected from 64 sampling sites to analyze the water quality in estuaries along the coast of the Bohai Sea,North China.The twenty-five water quality parameters ...High-dimensional data(a dataset with many features)were collected from 64 sampling sites to analyze the water quality in estuaries along the coast of the Bohai Sea,North China.The twenty-five water quality parameters analyzed were collected monthly from January 2021 to December 2021.Multivariate statistical techniques,such as the absolute principal component score-multiple linear regression model(APCS-MLR),correlation analysis,and analysis of variance were used to identify and quantify the potential sources or factors affecting water quality and to analyze the spatial-temporal variation in water quality.The water quality indices(WQIs),ranging from 67.96 to 70.67,showed that the water quality was at an intermediate level in the estuaries during both the flood and nonflood seasons.The concentrations of total phosphorus(TP),ammonia N(AN),and organic pollutants were greater in the Haihe River Basin than in the Liaohe River and Huanghe-Huaihe River Basins.The concentration of total nitrogen(TN)in the Haihe River Basin was lower than that in the Liaohe River and Huanghe-Huaihe River Basins.Heavy metal concentrations in the Liaohe River Basin were greater than those in the Haihe River and Huanghe-Huaihe River Basins.The annual mean concentrations of AN in the estuaries of the Haihe,Liaohe,and Huanghe(Yellow)rivers exhibited significant decreasing trends from 2013 to 2022,but no significant decreasing trends were found for permanganate index(COD_(Mn))or the TP.The concentrations of TN and AN were lower in the flood season than in the nonflood season,and the TP concentration was greater in the flood season than in the nonflood season.However,the concentrations of organic pollutants did not exhibit significant differences.Domestic sewage and industrial wastewater,substance exchange between air and water,nonpoint sources from rural and urban areas,and aquaculture wastewater were the major sources or factors responsible for water pollution in the estuaries.展开更多
To develop a larger in-line plasma enhanced chemical vapor deposition(PECVD)device,the length of the linear microwave plasma source needs to be increased to 1550 mm.This paper proposes a solution to the problem of pla...To develop a larger in-line plasma enhanced chemical vapor deposition(PECVD)device,the length of the linear microwave plasma source needs to be increased to 1550 mm.This paper proposes a solution to the problem of plasma inhomogeneity caused by increasing device length.Based on the COMSOL Multiphysics,a multi-physics field coupling model for in-line PECVD device is developed and validated.The effects of microwave power,chamber pressure,and magnetic flux density on the plasma distribution are investigated,respectively,and their corresponding optimized values are obtained.This paper also presents a new strategy to optimize the wafer position to achieve the balance between deposition rate and film quality.Numerical results have indicated that increasing microwave power and magnetic flux density or decreasing chamber pressure all play positive roles in improving plasma homogeneity,and among them,the microwave power is the most decisive influencing factor.It is found that the plasma homogeneity is optimal under the condition of microwave power at 2000 W,chamber pressure at 15 Pa,and magnetic field strength at 45 mT.The relative deviation is within−3.7%to 3.9%,which fully satisfies the process requirements of the equipment.The best position for the wafer is 88 mm from the copper antenna.The results are very valuable for improving the quality of the in-line PECVD device.展开更多
Under the underdetermined blind sources separation(UBSS) circumstance,it is difficult to estimate the mixing matrix with high-precision because of unknown sparsity of signals.The mixing matrix estimation is proposed b...Under the underdetermined blind sources separation(UBSS) circumstance,it is difficult to estimate the mixing matrix with high-precision because of unknown sparsity of signals.The mixing matrix estimation is proposed based on linear aggregation degree of signal scatter plot without knowing sparsity,and the linear aggregation degree evaluation of observed signals is presented which obeys generalized Gaussian distribution(GGD).Both the GGD shape parameter and the signals' correlation features affect the observation signals sparsity and further affected the directionality of time-frequency scatter plot.So a new mixing matrix estimation method is proposed for different sparsity degrees,which especially focuses on unclear directionality of scatter plot and weak linear aggregation degree.Firstly,the direction of coefficient scatter plot by time-frequency transform is improved and then the single source coefficients in the case of weak linear clustering is processed finally the improved K-means clustering is applied to achieve the estimation of mixing matrix.The proposed algorithm reduces the requirements of signals sparsity and independence,and the mixing matrix can be estimated with high accuracy.The simulation results show the feasibility and effectiveness of the algorithm.展开更多
The abandoned smelters present a substantial pollution threat to the nearby soil and groundwater.In this study,63 surface soil samples were collected from a zinc smelter to quantitatively describe the pollution charac...The abandoned smelters present a substantial pollution threat to the nearby soil and groundwater.In this study,63 surface soil samples were collected from a zinc smelter to quantitatively describe the pollution characteristics,ecological risks,and source apportionment of heavy metal(loid)s(HMs).The results revealed that the average contents of Zn,Cd,Pb,As,and Hg were 0.4,12.2,3.3,5.3,and 12.7 times higher than the risk screening values of the construction sites,respectively.Notably,the smelter was accumulated heavily with Cd and Hg,and the contribution of Cd(0.38)and Hg(0.53)to ecological risk was 91.58%.ZZ3 and ZZ7 were the most polluted workshops,accounting for 25.7%and 35.0%of the pollution load and ecological risk,respectively.The influence of soil parent materials on pollution was minor compared to various workshops within the smelter.Combined with PMF,APCS-MLR and GIS analysis,four sources of HMs were identified:P1(25.5%)and A3(18.4%)were atmospheric deposition from the electric defogging workshop and surface runoff from the smelter;P2(32.7%)and A2(20.9%)were surface runoff of As-Pb foul acid;P3(14.5%)and A4(49.8%)were atmospheric deposition from the leach slag drying workshop;P4(27.3%)and A1(10.8%)were the smelting process of zinc products.This paper described the distribution characteristics and specific sources of HMs in different process workshops,providing a new perspective for the precise remediation of the smelter by determining the priority control factors.展开更多
Monitoring sensors in complex engineering environments often record abnormal data,leading to significant positioning errors.To reduce the influence of abnormal arrival times,we introduce an innovative,outlier-robust l...Monitoring sensors in complex engineering environments often record abnormal data,leading to significant positioning errors.To reduce the influence of abnormal arrival times,we introduce an innovative,outlier-robust localization method that integrates kernel density estimation(KDE)with damping linear correction to enhance the precision of microseismic/acoustic emission(MS/AE)source positioning.Our approach systematically addresses abnormal arrival times through a three-step process:initial location by 4-arrival combinations,elimination of outliers based on three-dimensional KDE,and refinement using a linear correction with an adaptive damping factor.We validate our method through lead-breaking experiments,demonstrating over a 23%improvement in positioning accuracy with a maximum error of 9.12 mm(relative error of 15.80%)—outperforming 4 existing methods.Simulations under various system errors,outlier scales,and ratios substantiate our method’s superior performance.Field blasting experiments also confirm the practical applicability,with an average positioning error of 11.71 m(relative error of 7.59%),compared to 23.56,66.09,16.95,and 28.52 m for other methods.This research is significant as it enhances the robustness of MS/AE source localization when confronted with data anomalies.It also provides a practical solution for real-world engineering and safety monitoring applications.展开更多
Formaldehyde（HCHO） is one of the most important intermediate products of atmospheric photochemical reactions in the troposphere, therefore understanding of HCHO sources is essential for effective ozone control measu...Formaldehyde（HCHO） is one of the most important intermediate products of atmospheric photochemical reactions in the troposphere, therefore understanding of HCHO sources is essential for effective ozone control measures. The objective of this work is to distinguish between primary and secondary sources of HCHO. Based on about one month of online measurements in winter in Ziyang,Sichuan, the multi-linear regression analysis of ambient concentrations of HCHO and possible tracers（acetonitrile, propane and peroxyacetyl nitrate） was performed. The results show that during winter in Ziyang, biomass burning contributed an average of 53.2% to ambient HCHO levels, while secondary processes contributed about 30.1%, and vehicular sources accounted for 7.1%.展开更多
Based on the data synthesis simulation and the actual processing of the airgun seismic source signal,three quantitative indicators of signal-to-noise ratio,waveform correlation coefficient and phase offset,are superim...Based on the data synthesis simulation and the actual processing of the airgun seismic source signal,three quantitative indicators of signal-to-noise ratio,waveform correlation coefficient and phase offset,are superimposed. We systematically evaluate the functions of the following three stack methods including linearity,phase weighting and S-transform in the extraction of weak signals under strong background noise and quantitatively estimate the reliability of the stack results. Through the comprehensive discussion of the above three methods of stack results,the preliminary comparative analysis believes that the linear stack signal-to-noise ratio is low,but the waveform distortion is minimal; the phase-weighted superimposed signal-to-noise ratio is high and the phase offset is small,but the results of the waveform quality and linear stack are larger than the deviation; the S-transform stack has a relatively higher signal-to-noise ratio and a small loss of waveform amplitude,but there is a certain phase shift phenomenon. It is therefore suggested that linear stack technology should be used when the requirements of both waveform quality and time precision are high. However,the selection of the stack method when the airgun source excitation is limited should be emphasized. If high fidelity is required, the S-transform stack method should be selected; if the required time is high,accuracy can be selected by phase-weighted stack method to achieve reasonable extraction of weak signals.展开更多
Using 132-member experiments based on a linear baroclinic atmospheric model(LBM), this study investigates the optimal heat source forcing the interannual variability of the western North Pacific summer monsoon(WNPSM)....Using 132-member experiments based on a linear baroclinic atmospheric model(LBM), this study investigates the optimal heat source forcing the interannual variability of the western North Pacific summer monsoon(WNPSM). The 132 members are forced by localized atmospheric heat sources distributed homogeneously over regions from 55°S to 55°N, each 10° latitude × 30° longitude in size. The atmospheric responses to all the heating constitute an ensemble to examine the relative contribution of each local heat source to the strength of the WNPSM. The result indicates that the combination of an atmospheric heating(cooling) source over the subtropical Northwest Pacific and a cooling(heating) source over the tropical Indian Ocean and the midlatitudes from China to the southern part of Japan is the pattern most effective at enhancing(weakening) the WNPSM.Besides, the optimal heat source pattern identified by the LBM simulations is similar to the observed atmospheric heating anomalies associated with WNPSM interannual variability. The results suggest that any external forcing that leads to a similar heating structure as the optimal thermal forcing pattern could lead to an anomalous WNPSM.展开更多
In high-energy flash radiography,scattered photons degrade the acquiring image,which limits the resolving power of interfaces and density of dense object.The application of large anti-scatter grid can reduce the scatt...In high-energy flash radiography,scattered photons degrade the acquiring image,which limits the resolving power of interfaces and density of dense object.The application of large anti-scatter grid can reduce the scattered photons remarkably,but this requires a stable source position in order to reduce the loss of signal photons in the grid structure.The pinhole imaging technique is applied to observe spatial jitters of a triple-pulse radiographic source of a linear induction accelerator.Numerical simulations are conducted to analyze the imaging performance with the same or close parameters of the pinhole object and experimental alignment.Experiments are carried out to observe spatial jitters of the source between different measurements.Deviations of the source position between different pulses are measured in each experiment.展开更多
In order to more easily highlight the influence of cooled ambient air through an air-ground heat exchanger on the process of diffusion and mixing of heat around an electronic component and a photovoltaic solar module,...In order to more easily highlight the influence of cooled ambient air through an air-ground heat exchanger on the process of diffusion and mixing of heat around an electronic component and a photovoltaic solar module, we undertook to study the thermal field beforehand. The turbulent model has applied a realizable k-ε two equations model and the two-dimensional Reynolds Averaged Navier-Stokes (RANS) equations are discretized with the second order upwind scheme. The SIMPLE algorithm, which is developed using control volumes, is adopted as the numerical procedure. Calculations were performed for a wide variation of the Reynolds numbers. Our results reveal, on the one hand, that the use of an air-ground heat exchanger accelerates the dispersion of the thermal field around the PV panel. On the other hand, with increasing Reynolds number, the instabilities appear in the wake zone, showing an oscillatory flow, also called von Karman Vortex Street. Our air-ground heat exchanger has an important influence on the diffusion process of the thermal field. Comparison of numerical results with the experimental data available in the literature is satisfactory.展开更多
We have designed,assembled,and tested a 4-MA,60-ns fast linear transformer driver(LTD),which is the first operating generator featuring multiple LTD modules connected in parallel.The LTD-based accelerator comprises si...We have designed,assembled,and tested a 4-MA,60-ns fast linear transformer driver(LTD),which is the first operating generator featuring multiple LTD modules connected in parallel.The LTD-based accelerator comprises six modules in parallel,each of which has ten-stage cavities stacked in series.The six LTD modules are connected to a water tank of diameter 6 m via a 3-m-long impedance-matched deionized waterinsulated coaxial transmission line.In the water tank,the electrical pulses are transmitted down by six horizontal tri-plate transmission lines.A 2.1-m-diameter two-level vacuum insulator stack is utilized to separate the deionized water region from the vacuum region.In the vacuum,the currents are further transported downstream by a two-level magnetically insulated transmission-line and then converged through four post-hole convolutes.Plasma radiation loads or bremsstrahlung electron beam diodes serve as loads that are expected to generate intense soft X rays or warm X rays.The machine is 3.2 m in height and 22 m in outer diameter,including support systems such as a high-voltage charge supply,magnetic core reset system,trigger system,and support platform for inner stalk installation and maintenance.A total of 1440 individual±100-kV multi-gap spark switches and 2880 individual 100-kV capacitors are employed in the accelerator.A total of 12 fiberoptic laser-controlled trigger generators combining photoconductive and traditional gas spark switch technologies are used to realize the synchronous discharge of the more than 1000 gas switches.At an LTD charge voltage of±85 kV,the accelerator stores an initial energy of about 300 kJ and is expected to deliver a current of 3–5 MA into various loads.To date,the LTD facility has shot into a thick-walled aluminum liner load and a reflex triode load.With a thick-walled aluminum liner of inductance 1.81 nH,a current with peak up to 4.1 MA and rise time(10%–90%)of about 60 ns has been achieved.The current transport efficiency from the insulator stack to the liner load approaches 100%during peak times.The LTD accelerator has been used to drive reflex triode loads generating warm X rays with high energy fluence and large radiation area.It has been demonstrated that this LTD is a promising and high-efficiency prime pulsed power source suitable for use in constructing the next generation of large-scale accelerators with currents of tens of megaamperes.展开更多
Rainfall is an important factor in estimating the event mean concentration （EMC） which is used to quantify the washed-off pollutant concentrations from non-point sources （NPSs）. Pollutant loads could also be calcu...Rainfall is an important factor in estimating the event mean concentration （EMC） which is used to quantify the washed-off pollutant concentrations from non-point sources （NPSs）. Pollutant loads could also be calculated using rainfall, catchment area and runoff coefficient. In this study, runoff quantity and quality data gathered from a 28-month monitoring conducted on the road and parking lot sites in Korea were evaluated using multiple linear regression （MLR） to develop equations for estimating pollutant loads and EMCs as a function of rainfall variables. The results revealed that total event rainfall and average rainfall intensity are possible predictors of pollutant loads. Overall, the models are indicators of the high uncertainties of NPSs; perhaps estimation of EMCs and loads could be accurately obtained by means of water quality sampling or a long term monitoring is needed to gather more data that can be used for the development of estimation models.展开更多
Presented field-circuit coupled adaptive time-stepping finite element method to study on permanent magnet linear synchronous motor (PMLSM) characteristics fed by SPWM voltage source inverter.In air-gap field where the...Presented field-circuit coupled adaptive time-stepping finite element method to study on permanent magnet linear synchronous motor (PMLSM) characteristics fed by SPWM voltage source inverter.In air-gap field where the direction or magnitude of the field is changing rapidly,the smallest elements are demanded due to high accuracy to use adaptive meshing technique.The co-simulation was used with the status space functions and time-step finite element functions,in which time-step of the status space functions was the smallest than finite element functions'.The magnitude relation of the normal elec- tromagnetic force and tangential electromagnetic force and the period were attained,and current curve was very abrupt at current zero area due to the bigger resistance and leak- age reactance,including main characteristics of motor voltage and velocity.The simulation results compare triumphantly with the experiments results.展开更多
This paper presents a novel method that is applied to realize the Linear Transformation(LT)Switched-Capacitor Filter(SCF).It adopts the Voltage Control Voltage Source(VCVS)equalized transfor-mation to revise the origi...This paper presents a novel method that is applied to realize the Linear Transformation(LT)Switched-Capacitor Filter(SCF).It adopts the Voltage Control Voltage Source(VCVS)equalized transfor-mation to revise the original LC ladder filter and induce it into 16 basic sections and then extend the princi-ple of the LT in order to fit active and 3 port networks and give out switched-capacitor circuits corre-sponding to the 16 basic sections,which can realize all four kinds of filters——LP,HP,BP,BS filters.De-signed examples are given here.An Nth order filter only requires N amplifiers and the circuit is insensitive toparasitic capacitances.The experimental results of a 3rd order elliptic LP and a 6th order elliptic BP are giv-en and agree with the theory.展开更多
Linear source location of acoustic emission (AE) technique has been applied in the present paper for finding the source of material damage under fatigue loading. A plate type structure of ductile cast iron has been us...Linear source location of acoustic emission (AE) technique has been applied in the present paper for finding the source of material damage under fatigue loading. A plate type structure of ductile cast iron has been used to undergo fatigue damage in a servopulsing machine in the experiment. AE sensors were attached to the specimen for getting the time delay of AE signal propagations through the specimen. After receiving the time delay data of AE signals due to the damage initiation in the material for the provided fatigue loads, linear source location algorithm has been applied and the crack positions are identified. Before applying the technique, a series of pencil lead breaks (PLBs) tests have been conducted upon a ductile cast iron plate of same dimension for verifying the applied algorithm. According to the PLBs varification, the failure location of ductile cast iron (pearlite type) due to the fatigue loading has been characterized. In both experiments, the active ability of the proposed technique for source location of structural damage has been identified clearly and successfully.展开更多
Purpose To propose a method for simultaneous fluorescence and Compton scattering computed tomography by using linearly polarized X-rays.Methods Monte Carlo simulations were adopted to demonstrate the feasibility of th...Purpose To propose a method for simultaneous fluorescence and Compton scattering computed tomography by using linearly polarized X-rays.Methods Monte Carlo simulations were adopted to demonstrate the feasibility of the proposed method.In the simulations,the phantom is a polytetrafluoroethylene cylinder inside which are cylindrical columns containing aluminum,water,and gold(Au)-loaded water solutions with Au concentrations ranging between 0.5 and 4.0 wt%,and a parallel-hole collimator imaging geometry was adopted.The light source was modeled based on a Thomson scattering X-ray source.The phantom images for both imaging modalities were reconstructed using a maximumlikelihood expectation maximization algorithm.Results Both the X-ray fluorescence computed tomography(XFCT)and Compton scattering computed tomography(CSCT)images of the phantom were accurately reconstructed.A similar attenuation contrast problem for the different cylindrical columns in the phantom can be resolved in the XFCT and CSCT images.The interplay between XFCT and CSCT was analyzed,and the contrast-to-noise ratio(CNR)of the reconstruction was improved by correcting for the mutual influence between the two imaging modalities.Compared with K-edge subtraction imaging,XFCT exhibits a CNR advantage for the phantom.Conclusion Simultaneous XFCT and CSCT can be realized by using linearly polarized X-rays.The synergy between the two imaging modalities would have an important application in cancer radiation therapy.展开更多
Objective: To explore the significance of dual-energy CT non-linear fusion technique in improving the quality of CTA image of renal cancer. Methods: The CTA images of 100 patients who had been confirmed by pathology a...Objective: To explore the significance of dual-energy CT non-linear fusion technique in improving the quality of CTA image of renal cancer. Methods: The CTA images of 100 patients who had been confirmed by pathology as renal cancer were collected and were randomly divided into experimental group and control group with 50 cases respectively. The two groups of patients were treated with iodine concentration of 300 mg/ml and 350 mg/ml non-ionic contrast agent, with a dosage of 1.5 ml/kg and an injection rate of 4 ml/s. The contrast agent intelligently tracking method was adopted bolus. The control group used the conventional CTA scanning, with a reference tube voltage/tube current of 100 kv/ref150 mas. The experimental group adopted the double energy scanning, with ball tube A and ball tube B. The reference tube voltage/tube current was 100 kv/ref250 mas and sn150 kv/ref125 mas respectively. The images of the experimental group were non-linear fused to obtain the Mono+ 55 kev single-energy images. The CT value, SNR contrast ratio of the abdominal aorta, renal artery and tumor tissue of the experimental group images and the 100 KV images and the Mono+ 55 kev images of the control group were compared. The objective evaluation and subjective evaluation of the image quality of the three groups of images was performed. Results: The results showed that the 100 kV images of the experimental group were statistically different from those of the control group (P05) in CT value, SNR and CNR (P 0.05). And there was no statistically significant difference between the non-linear fusion single-energy Mono+ 55 kev images and the control group images in CT value, SNR and CNR (P > 0.05). The subjective evaluation of image quality showed that there was no significant difference between Mono+ 55 kev images and control group images, and the quality of Mono+ 55 kev images was higher than that of experimental group 100 kV images. Conclusion: The dual-energy CT non-linear fusion technique can improve the quality of CTA image in patients with renal cancer, and it is possible to obtain high quality CTA images with low iodine concentration contrast agent.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2022YFE03100002)the National Natural Science Foundation of China(Grant Nos.12435015 and 12075241)。
文摘This article presents the physics for determining an appropriate helicon plasma source for the linear experimental advanced device(LEAD)through tripartite mutual verification encompassing theoretical analysis,code simulation,and experimental validation.Using the HELIC code,plasma excitation processes were simulated with three antenna configurations:m=1 half-helix,m=1 Boswell,and m=0 single-loop helicon antennas,and complemented by theoretical analysis.Key parameters including plasma impedance(R_(p))and energy deposition profiles along radial(P_(r))and axial(P_(z))directions were comparatively analyzed,revealing significantly enhanced R_(p),P_(r),and P_(z) values for the loop antenna configuration as compared with other configurations.Wave propagation equation solutions predicted a primary plasma generation layer at the antenna center;numerical simulations identified an additional plasma formation region at the antenna boundary,indicative of edge Landau damping effects.Interestingly,stronger axial magnetic fields do not necessarily result in higher plasma densities,especially for m=0 antenna configurations.Experimental validation conducted with an m=0 multi-loop plasma source confirmed these findings.Both theoretical analyses and experimental studies on large-volume plasma generation utilizing this innovative source elucidated the underlying mechanisms responsible for the remarkable low mode transition threshold of 150-watt input power and demonstrated significantly enhanced plasma confinement properties.
基金supported by National Natural Science Foundation of China(No.11205201)
文摘By utilization of different excitation power sources, linear plasma sources can be differentiated into DC, RF, VHF, microwave and dual frequency types. Through installing several linear plasma sources in parallel or adopting the so-called roll-to-roll （air-to-air） process, scale uniform linear plasma sources were realized and successfully applied to the deposition of large area uniform dielectric thin films, Furthermore, the magnetic field system can effectively reduce the recombination losses on the wall of the vacuum chamber and enhance the plasma density. Linear plasma sources with approximately one square meter deposition area with the plasma density of 1011 cm 3 have been developed, some of which have been used for the deposition of dielectric layers and large area plasma etching.
文摘The double pulse sources （DPS） method is presented for linear track estimation in this work. In the field of noise identification of underwater moving target, the Doppler will distort the frequency and amplitude of the radiated noise. To eliminate this, the track estimation is necessary. In the DPS method, we first estimate bearings of two sinusoidal pulse sources installed in the moving target through baseline positioning method. Meanwhile, the emitted and recorded time of each pulse are also acquired. Then the linear track parameters will be achieved based on the geometry pattern with the help of double sources spacing. The simulated results confirm that the DPS improves the performance of the previous double source spacing method. The simulated experiments were carried out using a moving battery car to further evaluate its performance. When the target is 40-60m away, the experiment results show that biases of track azimuth and abeam distance of DPS are under 0.6° and 3.4m, respectively. And the average deviation of estimated velocity is around 0.25m/s.
基金Supported by the National Natural Science Foundation of China(No.41571479)。
文摘High-dimensional data(a dataset with many features)were collected from 64 sampling sites to analyze the water quality in estuaries along the coast of the Bohai Sea,North China.The twenty-five water quality parameters analyzed were collected monthly from January 2021 to December 2021.Multivariate statistical techniques,such as the absolute principal component score-multiple linear regression model(APCS-MLR),correlation analysis,and analysis of variance were used to identify and quantify the potential sources or factors affecting water quality and to analyze the spatial-temporal variation in water quality.The water quality indices(WQIs),ranging from 67.96 to 70.67,showed that the water quality was at an intermediate level in the estuaries during both the flood and nonflood seasons.The concentrations of total phosphorus(TP),ammonia N(AN),and organic pollutants were greater in the Haihe River Basin than in the Liaohe River and Huanghe-Huaihe River Basins.The concentration of total nitrogen(TN)in the Haihe River Basin was lower than that in the Liaohe River and Huanghe-Huaihe River Basins.Heavy metal concentrations in the Liaohe River Basin were greater than those in the Haihe River and Huanghe-Huaihe River Basins.The annual mean concentrations of AN in the estuaries of the Haihe,Liaohe,and Huanghe(Yellow)rivers exhibited significant decreasing trends from 2013 to 2022,but no significant decreasing trends were found for permanganate index(COD_(Mn))or the TP.The concentrations of TN and AN were lower in the flood season than in the nonflood season,and the TP concentration was greater in the flood season than in the nonflood season.However,the concentrations of organic pollutants did not exhibit significant differences.Domestic sewage and industrial wastewater,substance exchange between air and water,nonpoint sources from rural and urban areas,and aquaculture wastewater were the major sources or factors responsible for water pollution in the estuaries.
基金by Hunan Provincial Science and Technology Department'Key Field Research and Development Project'(No.2019WK2011)。
文摘To develop a larger in-line plasma enhanced chemical vapor deposition(PECVD)device,the length of the linear microwave plasma source needs to be increased to 1550 mm.This paper proposes a solution to the problem of plasma inhomogeneity caused by increasing device length.Based on the COMSOL Multiphysics,a multi-physics field coupling model for in-line PECVD device is developed and validated.The effects of microwave power,chamber pressure,and magnetic flux density on the plasma distribution are investigated,respectively,and their corresponding optimized values are obtained.This paper also presents a new strategy to optimize the wafer position to achieve the balance between deposition rate and film quality.Numerical results have indicated that increasing microwave power and magnetic flux density or decreasing chamber pressure all play positive roles in improving plasma homogeneity,and among them,the microwave power is the most decisive influencing factor.It is found that the plasma homogeneity is optimal under the condition of microwave power at 2000 W,chamber pressure at 15 Pa,and magnetic field strength at 45 mT.The relative deviation is within−3.7%to 3.9%,which fully satisfies the process requirements of the equipment.The best position for the wafer is 88 mm from the copper antenna.The results are very valuable for improving the quality of the in-line PECVD device.
基金Supported by the National Natural Science Foundation of China(No.51204145)Natural Science Foundation of Hebei Province of China(No.2013203300)
文摘Under the underdetermined blind sources separation(UBSS) circumstance,it is difficult to estimate the mixing matrix with high-precision because of unknown sparsity of signals.The mixing matrix estimation is proposed based on linear aggregation degree of signal scatter plot without knowing sparsity,and the linear aggregation degree evaluation of observed signals is presented which obeys generalized Gaussian distribution(GGD).Both the GGD shape parameter and the signals' correlation features affect the observation signals sparsity and further affected the directionality of time-frequency scatter plot.So a new mixing matrix estimation method is proposed for different sparsity degrees,which especially focuses on unclear directionality of scatter plot and weak linear aggregation degree.Firstly,the direction of coefficient scatter plot by time-frequency transform is improved and then the single source coefficients in the case of weak linear clustering is processed finally the improved K-means clustering is applied to achieve the estimation of mixing matrix.The proposed algorithm reduces the requirements of signals sparsity and independence,and the mixing matrix can be estimated with high accuracy.The simulation results show the feasibility and effectiveness of the algorithm.
基金This work was supported by the National Key Research and Development Program of China(No.2019YFC1803603).
文摘The abandoned smelters present a substantial pollution threat to the nearby soil and groundwater.In this study,63 surface soil samples were collected from a zinc smelter to quantitatively describe the pollution characteristics,ecological risks,and source apportionment of heavy metal(loid)s(HMs).The results revealed that the average contents of Zn,Cd,Pb,As,and Hg were 0.4,12.2,3.3,5.3,and 12.7 times higher than the risk screening values of the construction sites,respectively.Notably,the smelter was accumulated heavily with Cd and Hg,and the contribution of Cd(0.38)and Hg(0.53)to ecological risk was 91.58%.ZZ3 and ZZ7 were the most polluted workshops,accounting for 25.7%and 35.0%of the pollution load and ecological risk,respectively.The influence of soil parent materials on pollution was minor compared to various workshops within the smelter.Combined with PMF,APCS-MLR and GIS analysis,four sources of HMs were identified:P1(25.5%)and A3(18.4%)were atmospheric deposition from the electric defogging workshop and surface runoff from the smelter;P2(32.7%)and A2(20.9%)were surface runoff of As-Pb foul acid;P3(14.5%)and A4(49.8%)were atmospheric deposition from the leach slag drying workshop;P4(27.3%)and A1(10.8%)were the smelting process of zinc products.This paper described the distribution characteristics and specific sources of HMs in different process workshops,providing a new perspective for the precise remediation of the smelter by determining the priority control factors.
基金the financial support provided by the National Key Research and Development Program for Young Scientists(No.2021YFC2900400)Postdoctoral Fellowship Program of China Postdoctoral Science Foundation(CPSF)(No.GZB20230914)+2 种基金National Natural Science Foundation of China(No.52304123)China Postdoctoral Science Foundation(No.2023M730412)Chongqing Outstanding Youth Science Foundation Program(No.CSTB2023NSCQ-JQX0027).
文摘Monitoring sensors in complex engineering environments often record abnormal data,leading to significant positioning errors.To reduce the influence of abnormal arrival times,we introduce an innovative,outlier-robust localization method that integrates kernel density estimation(KDE)with damping linear correction to enhance the precision of microseismic/acoustic emission(MS/AE)source positioning.Our approach systematically addresses abnormal arrival times through a three-step process:initial location by 4-arrival combinations,elimination of outliers based on three-dimensional KDE,and refinement using a linear correction with an adaptive damping factor.We validate our method through lead-breaking experiments,demonstrating over a 23%improvement in positioning accuracy with a maximum error of 9.12 mm(relative error of 15.80%)—outperforming 4 existing methods.Simulations under various system errors,outlier scales,and ratios substantiate our method’s superior performance.Field blasting experiments also confirm the practical applicability,with an average positioning error of 11.71 m(relative error of 7.59%),compared to 23.56,66.09,16.95,and 28.52 m for other methods.This research is significant as it enhances the robustness of MS/AE source localization when confronted with data anomalies.It also provides a practical solution for real-world engineering and safety monitoring applications.
文摘Formaldehyde（HCHO） is one of the most important intermediate products of atmospheric photochemical reactions in the troposphere, therefore understanding of HCHO sources is essential for effective ozone control measures. The objective of this work is to distinguish between primary and secondary sources of HCHO. Based on about one month of online measurements in winter in Ziyang,Sichuan, the multi-linear regression analysis of ambient concentrations of HCHO and possible tracers（acetonitrile, propane and peroxyacetyl nitrate） was performed. The results show that during winter in Ziyang, biomass burning contributed an average of 53.2% to ambient HCHO levels, while secondary processes contributed about 30.1%, and vehicular sources accounted for 7.1%.
基金sponsored by the Spark Program of Earthquake Science and Technology,CEA(XH16003)the National Natural Science Foundation(NNSF) of China under Grant No.41474087
文摘Based on the data synthesis simulation and the actual processing of the airgun seismic source signal,three quantitative indicators of signal-to-noise ratio,waveform correlation coefficient and phase offset,are superimposed. We systematically evaluate the functions of the following three stack methods including linearity,phase weighting and S-transform in the extraction of weak signals under strong background noise and quantitatively estimate the reliability of the stack results. Through the comprehensive discussion of the above three methods of stack results,the preliminary comparative analysis believes that the linear stack signal-to-noise ratio is low,but the waveform distortion is minimal; the phase-weighted superimposed signal-to-noise ratio is high and the phase offset is small,but the results of the waveform quality and linear stack are larger than the deviation; the S-transform stack has a relatively higher signal-to-noise ratio and a small loss of waveform amplitude,but there is a certain phase shift phenomenon. It is therefore suggested that linear stack technology should be used when the requirements of both waveform quality and time precision are high. However,the selection of the stack method when the airgun source excitation is limited should be emphasized. If high fidelity is required, the S-transform stack method should be selected; if the required time is high,accuracy can be selected by phase-weighted stack method to achieve reasonable extraction of weak signals.
基金The study was jointly supported by the Strategic Priority Research Program of the Chinese Academy of Sciences[grant number XDA20060502]the National Natural Science Foundation of China[grant numbers 41425086,41661144016,and 41706026]the State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology,Chinese Academy of Sciences[project number LTO1704].
文摘Using 132-member experiments based on a linear baroclinic atmospheric model(LBM), this study investigates the optimal heat source forcing the interannual variability of the western North Pacific summer monsoon(WNPSM). The 132 members are forced by localized atmospheric heat sources distributed homogeneously over regions from 55°S to 55°N, each 10° latitude × 30° longitude in size. The atmospheric responses to all the heating constitute an ensemble to examine the relative contribution of each local heat source to the strength of the WNPSM. The result indicates that the combination of an atmospheric heating(cooling) source over the subtropical Northwest Pacific and a cooling(heating) source over the tropical Indian Ocean and the midlatitudes from China to the southern part of Japan is the pattern most effective at enhancing(weakening) the WNPSM.Besides, the optimal heat source pattern identified by the LBM simulations is similar to the observed atmospheric heating anomalies associated with WNPSM interannual variability. The results suggest that any external forcing that leads to a similar heating structure as the optimal thermal forcing pattern could lead to an anomalous WNPSM.
文摘In high-energy flash radiography,scattered photons degrade the acquiring image,which limits the resolving power of interfaces and density of dense object.The application of large anti-scatter grid can reduce the scattered photons remarkably,but this requires a stable source position in order to reduce the loss of signal photons in the grid structure.The pinhole imaging technique is applied to observe spatial jitters of a triple-pulse radiographic source of a linear induction accelerator.Numerical simulations are conducted to analyze the imaging performance with the same or close parameters of the pinhole object and experimental alignment.Experiments are carried out to observe spatial jitters of the source between different measurements.Deviations of the source position between different pulses are measured in each experiment.
文摘In order to more easily highlight the influence of cooled ambient air through an air-ground heat exchanger on the process of diffusion and mixing of heat around an electronic component and a photovoltaic solar module, we undertook to study the thermal field beforehand. The turbulent model has applied a realizable k-ε two equations model and the two-dimensional Reynolds Averaged Navier-Stokes (RANS) equations are discretized with the second order upwind scheme. The SIMPLE algorithm, which is developed using control volumes, is adopted as the numerical procedure. Calculations were performed for a wide variation of the Reynolds numbers. Our results reveal, on the one hand, that the use of an air-ground heat exchanger accelerates the dispersion of the thermal field around the PV panel. On the other hand, with increasing Reynolds number, the instabilities appear in the wake zone, showing an oscillatory flow, also called von Karman Vortex Street. Our air-ground heat exchanger has an important influence on the diffusion process of the thermal field. Comparison of numerical results with the experimental data available in the literature is satisfactory.
基金supported by the National Natural Science Foundation of China(Grant Nos.12027811 and 51790524).
文摘We have designed,assembled,and tested a 4-MA,60-ns fast linear transformer driver(LTD),which is the first operating generator featuring multiple LTD modules connected in parallel.The LTD-based accelerator comprises six modules in parallel,each of which has ten-stage cavities stacked in series.The six LTD modules are connected to a water tank of diameter 6 m via a 3-m-long impedance-matched deionized waterinsulated coaxial transmission line.In the water tank,the electrical pulses are transmitted down by six horizontal tri-plate transmission lines.A 2.1-m-diameter two-level vacuum insulator stack is utilized to separate the deionized water region from the vacuum region.In the vacuum,the currents are further transported downstream by a two-level magnetically insulated transmission-line and then converged through four post-hole convolutes.Plasma radiation loads or bremsstrahlung electron beam diodes serve as loads that are expected to generate intense soft X rays or warm X rays.The machine is 3.2 m in height and 22 m in outer diameter,including support systems such as a high-voltage charge supply,magnetic core reset system,trigger system,and support platform for inner stalk installation and maintenance.A total of 1440 individual±100-kV multi-gap spark switches and 2880 individual 100-kV capacitors are employed in the accelerator.A total of 12 fiberoptic laser-controlled trigger generators combining photoconductive and traditional gas spark switch technologies are used to realize the synchronous discharge of the more than 1000 gas switches.At an LTD charge voltage of±85 kV,the accelerator stores an initial energy of about 300 kJ and is expected to deliver a current of 3–5 MA into various loads.To date,the LTD facility has shot into a thick-walled aluminum liner load and a reflex triode load.With a thick-walled aluminum liner of inductance 1.81 nH,a current with peak up to 4.1 MA and rise time(10%–90%)of about 60 ns has been achieved.The current transport efficiency from the insulator stack to the liner load approaches 100%during peak times.The LTD accelerator has been used to drive reflex triode loads generating warm X rays with high energy fluence and large radiation area.It has been demonstrated that this LTD is a promising and high-efficiency prime pulsed power source suitable for use in constructing the next generation of large-scale accelerators with currents of tens of megaamperes.
基金provided by the Korean Ministry of Environment and Eco Star Project
文摘Rainfall is an important factor in estimating the event mean concentration （EMC） which is used to quantify the washed-off pollutant concentrations from non-point sources （NPSs）. Pollutant loads could also be calculated using rainfall, catchment area and runoff coefficient. In this study, runoff quantity and quality data gathered from a 28-month monitoring conducted on the road and parking lot sites in Korea were evaluated using multiple linear regression （MLR） to develop equations for estimating pollutant loads and EMCs as a function of rainfall variables. The results revealed that total event rainfall and average rainfall intensity are possible predictors of pollutant loads. Overall, the models are indicators of the high uncertainties of NPSs; perhaps estimation of EMCs and loads could be accurately obtained by means of water quality sampling or a long term monitoring is needed to gather more data that can be used for the development of estimation models.
基金National Natural Sciences Foundation(60474043)Henan Province Science Fund for Distinguished Young Scholars(0412002200)Henan Province Major Projects(0223025300)
文摘Presented field-circuit coupled adaptive time-stepping finite element method to study on permanent magnet linear synchronous motor (PMLSM) characteristics fed by SPWM voltage source inverter.In air-gap field where the direction or magnitude of the field is changing rapidly,the smallest elements are demanded due to high accuracy to use adaptive meshing technique.The co-simulation was used with the status space functions and time-step finite element functions,in which time-step of the status space functions was the smallest than finite element functions'.The magnitude relation of the normal elec- tromagnetic force and tangential electromagnetic force and the period were attained,and current curve was very abrupt at current zero area due to the bigger resistance and leak- age reactance,including main characteristics of motor voltage and velocity.The simulation results compare triumphantly with the experiments results.
文摘This paper presents a novel method that is applied to realize the Linear Transformation(LT)Switched-Capacitor Filter(SCF).It adopts the Voltage Control Voltage Source(VCVS)equalized transfor-mation to revise the original LC ladder filter and induce it into 16 basic sections and then extend the princi-ple of the LT in order to fit active and 3 port networks and give out switched-capacitor circuits corre-sponding to the 16 basic sections,which can realize all four kinds of filters——LP,HP,BP,BS filters.De-signed examples are given here.An Nth order filter only requires N amplifiers and the circuit is insensitive toparasitic capacitances.The experimental results of a 3rd order elliptic LP and a 6th order elliptic BP are giv-en and agree with the theory.
文摘Linear source location of acoustic emission (AE) technique has been applied in the present paper for finding the source of material damage under fatigue loading. A plate type structure of ductile cast iron has been used to undergo fatigue damage in a servopulsing machine in the experiment. AE sensors were attached to the specimen for getting the time delay of AE signal propagations through the specimen. After receiving the time delay data of AE signals due to the damage initiation in the material for the provided fatigue loads, linear source location algorithm has been applied and the crack positions are identified. Before applying the technique, a series of pencil lead breaks (PLBs) tests have been conducted upon a ductile cast iron plate of same dimension for verifying the applied algorithm. According to the PLBs varification, the failure location of ductile cast iron (pearlite type) due to the fatigue loading has been characterized. In both experiments, the active ability of the proposed technique for source location of structural damage has been identified clearly and successfully.
基金supported by the National Natural Science Foundation of China(Nos.12375157,12027902,and 11905011)。
文摘Purpose To propose a method for simultaneous fluorescence and Compton scattering computed tomography by using linearly polarized X-rays.Methods Monte Carlo simulations were adopted to demonstrate the feasibility of the proposed method.In the simulations,the phantom is a polytetrafluoroethylene cylinder inside which are cylindrical columns containing aluminum,water,and gold(Au)-loaded water solutions with Au concentrations ranging between 0.5 and 4.0 wt%,and a parallel-hole collimator imaging geometry was adopted.The light source was modeled based on a Thomson scattering X-ray source.The phantom images for both imaging modalities were reconstructed using a maximumlikelihood expectation maximization algorithm.Results Both the X-ray fluorescence computed tomography(XFCT)and Compton scattering computed tomography(CSCT)images of the phantom were accurately reconstructed.A similar attenuation contrast problem for the different cylindrical columns in the phantom can be resolved in the XFCT and CSCT images.The interplay between XFCT and CSCT was analyzed,and the contrast-to-noise ratio(CNR)of the reconstruction was improved by correcting for the mutual influence between the two imaging modalities.Compared with K-edge subtraction imaging,XFCT exhibits a CNR advantage for the phantom.Conclusion Simultaneous XFCT and CSCT can be realized by using linearly polarized X-rays.The synergy between the two imaging modalities would have an important application in cancer radiation therapy.
文摘Objective: To explore the significance of dual-energy CT non-linear fusion technique in improving the quality of CTA image of renal cancer. Methods: The CTA images of 100 patients who had been confirmed by pathology as renal cancer were collected and were randomly divided into experimental group and control group with 50 cases respectively. The two groups of patients were treated with iodine concentration of 300 mg/ml and 350 mg/ml non-ionic contrast agent, with a dosage of 1.5 ml/kg and an injection rate of 4 ml/s. The contrast agent intelligently tracking method was adopted bolus. The control group used the conventional CTA scanning, with a reference tube voltage/tube current of 100 kv/ref150 mas. The experimental group adopted the double energy scanning, with ball tube A and ball tube B. The reference tube voltage/tube current was 100 kv/ref250 mas and sn150 kv/ref125 mas respectively. The images of the experimental group were non-linear fused to obtain the Mono+ 55 kev single-energy images. The CT value, SNR contrast ratio of the abdominal aorta, renal artery and tumor tissue of the experimental group images and the 100 KV images and the Mono+ 55 kev images of the control group were compared. The objective evaluation and subjective evaluation of the image quality of the three groups of images was performed. Results: The results showed that the 100 kV images of the experimental group were statistically different from those of the control group (P05) in CT value, SNR and CNR (P 0.05). And there was no statistically significant difference between the non-linear fusion single-energy Mono+ 55 kev images and the control group images in CT value, SNR and CNR (P > 0.05). The subjective evaluation of image quality showed that there was no significant difference between Mono+ 55 kev images and control group images, and the quality of Mono+ 55 kev images was higher than that of experimental group 100 kV images. Conclusion: The dual-energy CT non-linear fusion technique can improve the quality of CTA image in patients with renal cancer, and it is possible to obtain high quality CTA images with low iodine concentration contrast agent.
