A spatiotemporal evolution model of a short-circuit arc to a secondary arc based on the improved charge simulation method

The initial shape of the secondary arc considerably influences its subsequent shape.To establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence,theoretical and experimental analysis of the evolution process of the short-circuit arc to the secondary arc is critical.In this study,an improved charge simulation method was used to develop the internal-space electric-field model of the short-circuit arc.The intensity of the electric field was used as an independent variable to describe the initial shape of the secondary arc.A secondary arc evolution model was developed based on this model.Moreover,the accuracy of the model was evaluated by comparison with physical experimental results.When the secondary arc current increased,the arcing time and dispersion increased.There is an overall trend of increasing arc length with increasing arcing time.Nevertheless,there is a reduction in arc length during arc ignition due to short circuits between the arc columns.Furthermore,the arcing time decreased in the range of 0°-90°as the angle between the wind direction and the x-axis increased.This work investigated the method by which short-circuit arcs evolve into secondary arcs.The results can be used to develop the secondary arc evolution model and to provide both a technical and theoretical basis for secondary arc suppression.

An insulated-gate bipolar transistor model based on the finite-volume charge method

A finite-volume charge method has been proposed to simulate PIN diodes and insulated-gate bipolar transistor(IGBT)devices using SPICE simulators by extending the lumped-charge method.The new method assumes local quasi-neutrality in the undepleted N^(-)base region and uses the total collector current,the nodal hole density and voltage as the basic quantities.In SPICE implementation,it makes clear and accurate definitions of three kinds of nodes—the carrier density nodes,the voltage nodes and the current generator nodes—in the undepleted N^(-)base region.It uses central finite difference to approximate electron and hole current generators and sets up the current continuity equation in a control volume for every carrier density node in the undepleted N^(-)base region.It is easy to increase the number of nodes to describe the fast spatially varying carrier density in transient processes.We use this method to simulate IGBT devices in SPICE simulators and get a good agreement with technology computer-aided design simulations.

Spatial charge and compensation method in a whirler

Based on particle-in-cell simulation, we studied the motions of ions and electrons. The results have shown that electrons are bounded by a magnetic field and only a small number of electrons can pass through the whirler channel. The plasma becomes non-neutral when it is emitted from the whirler, and the spatial charge leads to a beam divergence, which is unfavorable for mass separation. In order to compensate the spatial charge, a cathode is designed to transmit electrons and the quasi-neutral plasma beam. Experiment results have demonstrated that the auxiliary cathode can obviously improve the compensation degree of the spatial charge.

Adaptability of n-γdiscrimination and filtering methods based on plastic scintillation

Neutrons have been extensively used in many fields,such as nuclear physics,biology,geology,medical science,and national defense,owing to their unique penetration characteristics.Gamma rays are usually accompanied by the detection of neutrons.The capability to discriminate neutrons from gamma rays is important for evaluating plastic scintillator neutron detectors because similar pulse shapes are generated from both forms of radiation in the detection system.The pulse signals measured by plastic scintillators contain noise,which decreases the accuracy of n-y discrimination.To improve the performance of n-y discrimination,the noise of the pulse signals should be filtered before the n-y discrimination process.In this study,the influences of the Fourier transform,wavelet transform,moving-average filter,and Kalman algorithm on the charge comparison method,fractal spectrum method,and back-propagation neural network methods were studied.It was found that the Fourier transform filtering algorithm exhibits better adaptability to the charge comparison method than others,with an increasing accuracy of 6.87%compared to that without the filtering process.Meanwhile,the Kalman filter offers an improvement of 3.04%over the fractal spectrum method,and the adaptability of the moving-average filter in backpropagation neural network discrimination is better than that in other methods,with an increase in 8.48%.The Kalman filtering algorithm has a significant impact on the peak value of the pulse,reaching 4.49%,and it has an insignificant impact on the energy resolution of the spectrum measurement after discrimination.

CsI-bowl:an ancillary detector for exit channel selection inγ-ray spectroscopy experiments

A particle detector array designed for light-charged particles, known as the CsI-bowl, was built for exit channel selection for in-beam γ-ray spectroscopy experiments. This device is composed of 64 CsI(Tl) detectors, organized in a structure reminiscent of a tea-bowl. High quantum efficiency photodiodes, characterized by their minimal mass, were employed to collect scintillation light. Its design, construction, particle identification resolution, and its effectiveness in relation to exit channel selection are described in this paper. In source tests, the optimal figure of merit for the identification of α-particles and γ-rays using the charge comparison method was found to be 3.3 and 12.1 for CsI detectors coupled to photodiodes and avalanche photodiodes, respectively. The CsI-bowl demonstrated effectiveness in identifying particles, specifically the emission of protons and α-particles in the58Ni(19F, xpyn) fusion–evaporation reaction, thereby enabling the selection of the desired exit channels.

交直流混合输电线路空间电场分析(英文)

As the transmission line corridors become more and more rare in China,it is now inevitable for people to construct HVAC-HVDC hybrid transmission lines.The research on the electric field around the transmission lines plays an important role in evaluating the electromagnetic environment nearby.However,few existing research now considered the mutual effect of HVAC-HVDC hybrid transmission lines.Thus,this research designed a program based on windows,which calculated the surface voltage gradient on the transmission lines and the electric field at ground level respectively.This research calculated the surface voltage gradient on the transmission lines by applying the improved method of successive images.For the electric field at ground level under AC transmission line,simulation charge method is used,while for the electric field at the ground level under DC transmission lines,deutsch assumption method is used.Comparing the results generated by the calculation with those in published literature,the program is reliable.Taking 500 kV transmission lines as an example,when considering the mutual effect of the HVAC-HVDC lines,the amplitude of the surface voltage gradient will increase by about 10%and the amplitude of the electric field at ground level will increase by about 8%,making the mutual effect of the AC and DC lines unneglectable. Larger part of the electric field at ground level under hybrid lines is produced by the DC line.Thus,in order to control the electric field at ground level under hybrid lines,it should pay more attention on that produced by the DC line.

Model and Emulation of the System for the Passive Electrostatic Detecting People Through the Medium

The plane medium and point charge are regarded as an integral system. The static field＇s distribution situation of the point charge is studied in the medium structure of plane division layers by using mirror image method, drawing the point charge＇s calculation expression of the electric potential in every medium space. The mathematics model of passive electrostatic detecting people through the medium （regular distance between the goal point charge and the medium） is established, using MATLAB software to carry out emulation of the model and analysing the result, establishing the theoretical foundation for studying the technology of the passive static detecting people through the wall.

Study of n-γ discrimination in low energy range(above 40 keVee) by charge comparison method with a BC501A liquid scintillation detector

A VME-based experiment system for n-y discrimination using the charge comparison method was established.A data acquisition program for controlling the programmable modules and processing data online via VME64X bus was developed through the use of Lab VIEW.The two-dimensional（2D） scatter plots of the charge in the slow component vs.the total charge from ^（241）Am-Be and 252Cf neutron sources are presented.The 2D scatter plots of the energy vs.the ratio of the charge in the slow component to the total charge of the pulses are also presented.The quality of n-γ discrimination was checked by the figure-of-merit,and the results showed good performance of n-γ discrimination at the low energy range.Neutrons and γ-rays were separated above 50 keVee（electron-equivalent energy）.The quality of n-γ discrimination has been improved compared with others＇ results at five energies（150,250,350,450,550 keVee）.

Image Charge Methods for a Three-Dielectric-Layer Hybrid Solvation Model of Biomolecules

This paper introduces a three dielectric layer hybrid solvation model for treating electrostatic interactions of biomolecules in solvents using the PoissonBoltzmann equation.In this model,an interior spherical cavity will contain the solute and some explicit solvent molecules,and an intermediate buffer layer and an exterior layer contain the bulk solvent.A special dielectric permittivity profile is used to achieve a continuous dielectric transition from the interior cavity to the exterior layer.The selection of this special profile using a harmonic interpolation allows an analytical solution of the model by generalizing the classical Kirkwood series expansion.Discrete image charges are used to speed up calculations for the electrostatic potential within the interior and buffer layer regions.Semi-analytical and least squares methods are used to construct an accurate discrete image approximation for the reaction field due to solvent with or without salt effects.In particular,the image charges obtained by the least squares method provide accurate approximations to the reaction field independent of the ionic concentration of the solvent.Numerical results are presented to validate the accuracy and effectiveness of the image charge methods.

Lower order three-dimensional Burgers equation having non-Maxwellian ions in dusty plasmas

The dust acoustic（DA） shock wave with dust charge fluctuations, non-Maxwellian ions, and non-isothermal electrons is studied theoretically. The perturbation technique is employed to derive the lower order three-dimensional（3D） Burgers equation, and shock wave solution is explored by the tan-hyperbolic method. The effects of flat trapped and trapped electron distributions in the presence of Maxwellian and non-Maxwellian ions on characteristics shock waves are observed. The temperature ratio of non-Maxwellian ion temperature and non-isothermal electron temperature is found to play an important role in forming the shock-like structure.

Co-doping method used to improve the charge transport balance in solution processed OLEDs

In this paper, co-doping method is used to improve the current efficiency of solution-processed organic light-emitting diodes(OLEDs). By changing the ratio of two thermally activated delayed fluorescent(TADF) emitters, we studied the performance of device and its mechanism. A solution processed OLED with a structure of indium tin oxide(ITO, 150 nm)/PEDOT:PSS(30 nm)/CBP:4 Cz IPN-x%:4 Cz PN-y%(30 nm)/TPBi(40 nm)/Li F(1 nm)/Al(100 nm) was fabricated. The current efficiencies of 26.6 cd/A and 26.4 cd/A were achieved by the devices with dopant ratio of 6% 4 Cz IPN:2% 4 Cz PN and 2% 4 Cz IPN:6% 4 Cz PN in emitting material layer(EML), respectively. By investigating the tendency of current density change in devices with different doping ratio, we suggested that the enhancement of the current efficiency should be due to the charge transport balance improvement induced by assist dopant in EML.

Digital pulse shape discrimination methods for n-γ separation in an EJ-301 liquid scintillation detector

A digital pulse shape discrimination system based on a programmable module NI-5772 has been established and tested with an EJ-301 liquid scintillation detector. The module was operated by running programs developed in Lab VIEW, with a sampling frequency up to 1.6 GS/s. Standard gamma sources ^22 Na,^137Cs and ^60 Co were used to calibrate the EJ-301 liquid scintillation detector, and the gamma response function was obtained. Digital algorithms for the charge comparison method and zero-crossing method have been developed. The experimental results show that both digital signal processing（DSP） algorithms can discriminate neutrons from γ-rays. Moreover,the zero-crossing method shows better n-γ discrimination at 80 ke Vee and lower, whereas the charge comparison method gives better results at higher thresholds. In addition, the figure-of-merit（FOM） for detectors of two different dimensions were extracted at 9 energy thresholds, and it was found that the smaller detector presented better n-γseparation for fission neutrons.

Simulation of particle flow in a bell-less type charging system of a blast furnace using the discrete element method

A three-dimensional model was established by the discrete element method （DEM） to analyze the flow and segregation of particles in a charging process in detail. The simulation results of the burden falling trajectory obtained by the model were compared with the industrial charging measurements to validate the applicability of the model. The flow behavior of particles from the weighing hopper to the top layer of a blast furnace and the heaping behavior were analyzed using this model. A radial segregation index （RSI） was used to evaluate the extent of the size segregation in the charging process. In addition, the influence of the chute inclination angle on the size segregation and burden profile during the charging process was investigated.

Structural analysis by Rietveld refinement of calcium and lanthanum phosphosilicate apatites

Britholites with the general formula Ca10-xLnx（PO4）6-x（SiO4）xF2, （0≤x≤6） are considered to be promising matrices for the confinement of the by-products in the nuclear industry. A thermodynamic study showed that the stability of these compounds de-creased as the substitution rate increased. The present work was an attempt to gain more information about the structural changes in-duced by the substitution, in order to understand the observed stability decrease. The samples were successfully synthesized as a sin-gle-phase apatite by a solid-state reaction between 1200 and 1400 °C. The structural refinement indicated that the La3＋ions preferen-tially occupied the 6（h） sites. A progressive shift of F-along the c-axis outside its ideal position occurred as a result of the substitution increase. This might be the cause of the observed stability decrease, especially as the energies of the La-O, La-F and Si-O bonds are higher than those of Ca-O, Ca-F and P-O. The distribution of La3＋ between the two non-equivalent sites was confirmed by the charge distribution method.

Surface states in TiO2 submicrosphere films and their effect on electron transport

Owing to their special three-dimensional network structure and high specific surface area,TiO2 submicrospheres have been widely used as electron conductors in photoanodes for solar cells.In recent years,utilization of TiO2 submicrospheres in solar cells has greatly boosted the photovoltaic performance.Inevitably,however,numerous surface states in the TiO2 network affect electron transport.In this work,the surface states in TiO2 submicrospheres were thoroughly investigated by charge extraction methods,and the results were confirmed by the cyclic voltammetry method.The results showed that ammonia can effectively reduce the number of surface states in TiO2 submicrospheres.Furthermore,in-depth characterizations indicate that ammonia shifts the conduction band toward a more positive potential and improves the interfacial charge transfer.Moreover,charge recombination is effectively prevented.Overall,the cell performance is essentially dependent on the effect of the surface states,which affects the electron transfer and recombination process.

An Optimal Charging/Discharging Strategy for Smart Electrical Car Parks

This paper presents a smart electrical car park model where the power flows among electrical vehicles(EVs)as well as between EVs and the main grid.Based on this model,an optimal charging/discharging scheme is proposed.The fluctuation of hourly electricity rates is considered in this strategy to select a proper charging/discharging rate for each EV with less expenditure during each charging period.The proposed smart electrical car park is able to buy or sell electricity in the form of active and/or reactive power,i.e.kWh and/or kVARh,from or to the main grid to improve the power quality.According to the current state of charge of the EV’s battery bank,customers and the grid demands,a control center makes the decisions and sends the instructions of specific charging/discharging mode to each charging station.The performance of the proposed charging/discharging algorithm is simulated in Matlab.A comparison between the proposed and the unregulated charging/discharging strategies has been implemented.The results demonstrate that the proposed scheme can achieve better economic profits for EV customers and increase the commercial benefits for the car park owner.

New test and analysis of position-sensitive-silicon-detector

We have tested and analyzed the properties of two-dimensional Position-Sensitive-silicon-Detector （PSD） with new integrated preamplifiers. The test demonstrates that the best position resolution for 5.5 MeV α particles is 1.7 mm （FWHM）, and the best energy resolution is 2.1%, which are notably better than the previously reported results. A scaling formula is introduced to make the absolute position calibration.