高占空比颗粒电场荷电的计算

采用包含颗粒间相互作用的等效场强代替原外场,利用点偶极子模型计算出高占空比颗粒表面的最大场强,并与有限元法的计算结果进行比较,结果表明,对于具有不同介电常数的颗粒来说,在颗粒占空比较高时,这种方法仍具有足够的精度.根据颗粒场致荷电的机理,进一步推导出计算高占空比颗粒电场饱和荷电量和随时间变化的荷电量的近似公式.结果表明,颗粒电场荷电量不仅随场强、颗粒粒径和介电常数的增大而增大,还随颗粒占空比的增大而增大;颗粒电场荷电的速率与颗粒占空比相关,占空比越大,荷电速率越大.

磁增强负电晕放电特性和荷电方式研究

研究了磁增强负电晕放电特征,分析了这一过程的放电特性和磁场对极间不同区域的影响,比较了磁增强预荷电器和传统的预荷电器对静电增强过滤器效率的影响.结果表明:在磁增强负电晕放电中,磁场能有效地提高负离子和自由电子的浓度;磁增强负电晕放电自由电子的拉莫运动提高了放电电极附近的电离程度,使放电电流明显增长,使更多的正离子在电晕区积累,形成了和原电场方向一致的正离子电场,进一步增强电离,电晕区中积累的正离子形成的电场削弱了荷电区原电场强度;磁场的应用对扩散荷电机制有增强作用,对电场荷电机制不利.

水雾荷电特性的试验研究

通过试验研究,总结出环状电极水雾荷电的特点和规律,为水雾荷电应用于湿式除尘提供了科学的依据。

脉冲放电粒子荷电机理的研究

脉冲电晕放电在脉冲期间产生大量的高能电子，形成粒子在电场中的电子荷电。依据粒子附近的电子密度Ｂｏｌｔｚｍａｎ分布和电子在粒子表面传输的速率方程，在电子的动能大于或等于粒子表面势垒能的边界条件基础上得到粒子在脉冲电晕场中粒子荷电的速率方程，并利用龙格库塔法求解荷电速率方程得到粒子在脉冲放电条件下的荷电量。计算结果表明脉冲放电下的粒子荷电量平均是直流电晕放电的离子荷电量的２０倍，最大荷电量是０５～１５μｍ范围内的粒子，荷电量是直流电晕的２６倍。这一结果不仅与Ｄａｖｉｄ的粒子自由电子荷电理论结果相似，而且与微细粒子电子荷电量测试结果基本一致。

静电除尘演示实验中粉尘带电机理

本文由静电学及统计力学的基础理论出发,分析了静电除尘演示实验中粉尘粒子荷电的过程及机理,给出了粉尘荷电的数学模型.

Enhancing an internal electric field by a solid solution strategy for steering bulk-charge flow and boosting photocatalytic activity of Bi_(24)O_(31)Cl_(x)Br_(10-x)

Constructing bismuth oxyhalide solid solutions with a single homogeneous phase have intrigued the research community;however,a deeper understanding of the intrinsic origin for improved bulk-charge separation is still unclear.Herein,a series of Bi_(24)O_(31)Cl_(x)Br_(10-x) solid solutions with the same structural characteristics were synthesized by crystal structure regulation.Combining density functional theory calculation,Kelvin probe force microscopy,and zeta potential testing results,an enhanced internal electric field(IEF)intensity between[Bi_(24)O_(31)]and[X]layers was achieved by changing halogen types and ratios.This greatly facilitated bulk-charge separation and transfer efficiency,which is significant for the degradation of phenolic organic pollutants.Owing to the enhanced IEF intensity,the charge carrier density of Bi_(24)O_(31)Cl_(4)Br_(6) was 33.1 and 4.7 times stronger than that of Bi_(24)O_(31)Cl_(10) and Bi_(24)O_(31)Br_(10),respectively.Therefore,Bi24O31Cl4Br6 had an optimal photoactivity for the degradation of bisphenol A,which was 6.21 and 2.71 times higher than those of Bi_(24)O_(31)Cl_(10) and Bi_(24)O_(31)Br_(10),respectively.Thus,this study revealed the intrinsic mechanism of the solid solution strategy for photocatalytic performance enhancement with respect to an IEF.

An effective CdS/Ti-Fe_(2)O_(3)heterojunction photoanode:Analyzing Z-scheme charge-transfer mechanism for enhanced photoelectrochemical water-oxidation activity

Z-scheme photocatalytic system has been regarded as a popular field of research in photoelectrochemical(PEC)water splitting.Among the many obstacles facing a Z-scheme photocatalytic system,the analysis methods of interfacial Z-scheme charge transfer still remain a significant challenge.Hence,in this study,CdS/Ti-Fe_(2)O_(3)heterojunction photoanodes are elaborately designed to explore the charge-transfer behavior in PEC water splitting.In this study,photophysical measurements,including the Kelvin probe measurement,surface photovoltage spectroscopy(SPV),and transient photovoltage spectroscopy(TPV),are used to monitor the migration behavior of photogenerated charges at the interface electric field of CdS/Ti-Fe_(2)O_(3)Z-scheme heterojunction photoanodes.The Kelvin probe and SPV measurements demonstrate that CdS/Ti-Fe_(2)O_(3)interfacial driving force favors the rapid transfer of photoexcited electrons to CdS.The double-beam strategy based on TPV indicates that more electrons of Ti-Fe_(2)O_(3)are combined with the holes of CdS owing to the intensive interface electric field.The results of these measurements successfully prove the Z-scheme migration mechanism of CdS/Ti-Fe_(2)O_(3)photoanodes.Benefiting from the desirable charge transfer at the interface electric field,CdS/Ti-Fe_(2)O_(3)photoanodes exhibit superior photocatalytic oxygen evolution reaction performance compared with that of pure Ti-Fe_(2)O_(3).The photocurrent density of the 25CdS/Ti-Fe_(2)O_(3)photoanode reaches 1.94 mA/cm^(2) at 1.23 V versus reversible hydrogen electrode without excess cocatalyst,and it is two times higher than that of pure Ti-Fe_(2)O_(3)photoanode.Therefore,an outstanding strategy is provided in this study to prove the Z-scheme charge-transfer mechanism of photocatalytic systems in PEC water splitting.

Effect of the interfacial electric field on the HER on Pt(111)modified with iron adatoms in alkaline media

The study of the hydrogen evolution reaction(HER)aimed to reach a deeper understanding of the parameters that control the rate of this reaction is of great importance given the technical relevance of hydrogen production as an energy vector in the so-called hydrogen economy.In previous works,laser-induced temperature jump(LITJ)experiments on Pt(111)modified with Ni(OH)_(2)in alkaline media have revealed the importance of the interfacial electric field in the rate of the HER.It was hypothesised that small amounts of Ni(OH)_(2)cause a decrease of the electric field because of a negative shift of the pzfc toward the onset of the hydrogen evolution.In this work,to test the validity of this hypothesis,the study has been extended to Pt(111)surfaces modified with Fe(OH)_(2).The modified surfaces have been studied voltammetrically,and the voltammetric charges have been analysed.The voltammograms show a peak in the hydrogen evolution region that suggest the transformation in the adlayer from Fe(II)to Fe(0).In agreement with the coulometric analysis,the voltammetric features in the OH adsorption region would be related with the oxidation to the+3 valence state.The results obtained with LITJ method reflect the existence of a strong interaction of the Fe oxophilic species with the water molecules,shifting the potential of maximum entropy away from the onset of the HER.Hence,the most catalytic surface is the one with the lowest Fe coverage.

Effect of Surface Charge on Flashover for Oil-Pressboard Insulation under AC-DC Combined Electric Field

For converter transformer, AC-DC combined electric field can trigger space charge accumulation on oil-impregnated pressboard interface. The accumulation of space charge on oil-pressboard interface can result in electric field distortion, trend to trigger surface discharge of barriers. This paper studied the influence of surface charge on flashover voltage of oil-impregnated pressboard under AC-DC combined electric field. The study finds that the flashover voltage of oil-pressboard interface under negative polarity DC superimposed AC electric field is higher than that.of positive DC superimposed AC voltage to form composite electric field. It was found that homopolar surface charge has been accumulated on the interface of oil-pressboard with positive or negative DC voltage through measuring surface potential by the electrostatic capacitive probe. The surface charge produced electric field in the opposite direction, which weakening the synthetic electric field strength. What＇s more, under the same conditions, the negative surface charge density oil-pressboard is much larger than the positive.

An electricity price model with consideration to load and gas price effects

Some characteristics of the electricity load and prices are studied, and the relationship between electricity prices and gas (fuel) prices is analyzed in this paper. Because electricity prices are strongly dependent on load and gas prices, the authors constructed a model for electricity prices based on the effects of these two factors; and used the Geometric Mean Reversion Brownian Motion (GMRBM) model to describe the electricity load process, and a Geometric Brownian Motion(GBM) model to describe the gas prices; deduced the price stochastic process model based on the above load model and gas price model. This paper also presents methods for parameters estimation, and proposes some methods to solve the model.

Electromagnetic Environmental Impact of 500-kV Double -Circuit Transmission Lines

The strength of the power frequency electric intensity and magnetic field of the 500-kV double circuit transmission lines was calculated by using the equivalent charge method and the Ampere's Law, and the environmental impact factors of the fields were evaluated. By optimizing the phase sequence, the frequency electric intensity and magnetic field strength can be reduced. Within a distance of 25 m from the center of the transmission line, the power frequency electric intensity and magnetic field strength fall off sharply with the distance increase. Finally, the best phase sequence and the minimum ground clearance of the transmission lines were obtained to meet the requirements of the least impact on envionment.

Spin-Polarized Carriers Injection from Ferromagnetic Metal into Organic Semiconductor

Charge carriers in organic semiconductor are different from that of traditional inorganic semiconductor. Based on three-current model, considering electrical field effect, we present a theoretical model to discuss spin-polarized injection from ferromagnetic electrode into organic semiconductor by analyzing electrochemical potential both in ferromagnetic electrode and organic semiconductors. The calculated result of this model shows effects of electrode＇s spin polarization, equilibrium value of polarons ratio, interracial conductance, bulk conductivity of materials and electrical field. It is found that we could get decent spin polarization with common ferromagnetic electrode by increasing equilibrium value of polarons ratio. We also find that large and matched bulk conductivity of organic semiconductor and electrode, small spin-dependent interracial conductance, and enough large electrical field are critical factors for increasing spin polarization.

燃煤锅炉湿式电除尘器脱除细颗粒物的数值模拟研究

针对某热电厂燃煤锅炉尾部的湿式电除尘器进行了除尘器内流场以及PM2.5颗粒物捕集状况的数值模拟。模拟结果与现场试验结果进行了对照,两者吻合较好,验证了数学模型的可靠性。模拟结果显示,除尘器内部结构、运行工况以及粒径对细颗粒物脱除效率影响较大。研究的湿式电除尘器对于1μm以下的颗粒物脱除效率可达60%以上,对于PM2.5脱除效率可达70%以上。

Heterophase engineering of SnO2/Sn3O4 drives enhanced carbon dioxide electrocatalytic reduction to formic acid

Sn-based electrocatalysts have been gaining increasing attention due to their potential contribution in the conversion of CO2 into HCOOH driven by sustainable energy sources;however,their actual capability to catalyze CO2 reduction reaction(CO2RR)still cannot meet the requirements of commercial-scale applications.Therefore developing Snbased catalyst is of vital importance.Herein,the sheet-like heterophase Sn O2/Sn3O4 with a high density of phase interfaces has been first engineered by a facile hydrothermal process,with Sn3O4 as the dominant phase.The evidences from experiments and theoretical simulation indicate that the charge redistribution and built-in electric field at heterophase interfaces boost CO2 adsorption and HCOO*formation,accelerate the charge transfer between the catalysts and reactants,and ultimately greatly elevate the intrinsic activity of the heterophase Sn O2/Sn3O4 towards CO2 RR.Meanwhile,the in-situ generated porous structure and metal Sn during CO2 RR improve the mass transmission within the interlayer volume and the conductivity of Sn O2/Sn3O4.The heterophase Sn O2/Sn3O4 displays high activity and selectivity for CO2 RR,achieving an improvement in CO2 reduction current density,88.3%Faradaic efficiency of HCOOH conversion at-0.9 VRHE,along with a long-term tolerance in CO2 RR.This study demonstrates that heterophase interface engineering is an efficient strategy to regulate advanced catalysts for different applications.

Multiple Image Method for the Two Conductor Spheres in a Uniform Electrostatic Field

A method using multiple mirror images of point charges is put forward to analyze the polarization of two identical conductor spheres in a uniform electrostatic field.By use of the method,the electric field distribution and the interaction force between two spheres can be calculated accurately even for very small gap between two spheres.Our results show that the magnitude of the product of the gap between two spheres and the local electric field in the center of the gap is approximately in the same order and the interaction between two spheres increases very fast as the two spheres are close to each other.We also show that the interaction force between two conductor spheres is almost same with that between two dielectric spheres with high permittivity.

Engineering of multiferroic BiFeO grain boundaries with head-to-head polarization configurations

Confined low dimensional charges with high density such as two-dimensional electron gas(2 DEG)at interfaces and charged domain walls in ferroelectrics show great potential to serve as functional elements in future nanoelectronics.However,stabilization and control of low dimensional charges is challenging,as they are usually subject to enormous depolarization fields.Here,we demonstrate a method to fabricate tunable charged interfaces with~77°,86°and 94°head-to-head polarization configurations in multiferroic Bi Fe O_(3) thin films by grain boundary engineering.The adjacent grains are cohesively bonded and the boundary is about 1 nm in width and devoid of any amorphous region.Remarkably,the polarization remains almost unchanged near the grain boundaries,indicating the polarization charges are well compensated,i.e.,there should be two-dimensional charge gas confined at grain boundaries.Adjusting the tilt angle of the grain boundaries enables tuning the angle of polarization configurations from 71°to 109°,which in turn allows the control of charge density at the grain boundaries.This general and feasible method opens new doors for the application of charged interfaces in next generation nanoelectronics.

Optimal short-term load dispatch strategy in wind farm

With the increasing number of wind farms in power systems, the scheduling of a single wind farm needs to be improved. For this end, this paper proposes an optimal short-term load dispatch strategy for a single wind farm. Firstly, considering the large number of wind units and the high dimensionality of the scheduling solutions, we analyze the unit load characteristics, from which we extract the unit load characteristic matrix, and then classify the wind power units with the FCM fuzzy clustering algorithm. Secondly, we define the running loss indicator and action loss indicator. Based on the prediction of wind power and the load instructions, we establish a unit commitment model in wind farm, and solve the model using a combination of the fuzzy clustering algorithm and genetic algorithm, which overcomes the difficulty of the high dimensionality of the solution in the wind farm scheduling problem, to obtain the optimal scheduling strategy. Finally, through the simulation of the scheduling strategy for a 45 MW wind farm, we demonstrate the feasibility and effectiveness of the proposed strategy.

Exact transformation optics by using electrostatics

We present a novel method for designing transformation optical devices based on electrostatics.An arbi-trary transformation of electrostatic field can lead to a new refractive index distribution,where wave-fronts and energy flux lines correspond to equipotential surfaces and electrostatic flux lines,respectively.Owing to scalar wave propagating exactly following an eikonal equation,wave optics and geometric optics share the same solutions in the devices.The method is utilized to design multipole lenses derived from multipoles in electrostatics.The source and drain in optics are considered as corre-sponding to positive charge and negative charge in the static field.By defining winding numbers in vir-tual and physical spaces,we explain the reason for some multipole lenses with illusion effects.Besides,we introduce an equipotential absorber to replace the drain to correspond to a negative charge with a grounded conductor.Therefore,it is a very general platform to design intriguing devices based on the combination of electrostatics and transformation optics.

Remove the water-induced traps toward improved performance in organic solar cells

Clusters of water molecules have low ionization energies because of stabilization of charge from the dipole moment of surrounding molecules,and thus can form potential traps resulting in the undesirable photovoltaic performance in organic solar cells(OSCs).Herein,we demonstrated a solvent-water evaporation(SWE)strategy,which can effectively remove the water-induced traps that are omnipresent in photoactive layers,leading to a significant improvement in device performance.A higher power conversion efficiency of 17.10%and a better device photostability are achieved by using this SWE method,as compared with the untreated binary PM6:Y6 system(15.83%).We highlight the water-related traps as a limiting factor for carrier transport and extraction properties,and further reveal the good universality of the SWE strategy applied into OSCs.In addition,organic light-emitting diodes and organic field-effect transistors are investigated to demonstrate the applicability of this SWE approach.This strategy presents a major step forward for advancing the field of organic electronics.