Impact of accumulated dust particles' charge on the photovoltaic module performance

This work is focused on analysing effect of accumulated dust particles' charge on PV module performance. In the Dundee University's laboratory, dust particles have been created through epoxy powder and charged by using corona and tribo-electric charging methods by varying the charge levels of the accumulated dust particles. The PV module output has analysed for finding a relation between charge levels of the accumulated dust particles and its output voltage. Obtained experimental results have shown that charge level of accumulated dust particles on PV module's have significant impact on its output and dust particle accumulations are not associated with panel tilt angle.     

Numerical simulation of space-charge dynamics in a gyrotron trap

The particle-in-cell (PIC) method is used to simulate the self-consistent accumulation and bunching of space charge in the trap of a gyrotron electron-optical system. It is shown that it is possible to generate charge bunches that oscillate along the direction of the magnetic field. The dependence of the characteristics of these oscillations on the magnitude of the electron current into the trap is determined, along with the effect of the accumulated charge on the velocity distribution of electrons in the current passing through the magnetic mirror. Satisfactory agreement with the experimental data is obtained. Zh. Tekh. Fiz. 67, 98–101 (September 1997)     

Geometric Landau-Zener interferometry

We propose a new type of interferometry, based on geometric phases accumulated by a periodically driven two-level system undergoing multiple Landau-Zener transitions. As a specific example, we study its implementation in a superconducting charge pump. We find that interference patterns appear as a function of the pumping frequency and the phase bias, and clearly manifest themselves in the pumped charge. We also show that the effects described should persist in the presence of realistic decoherence.     

Chargeability of ethanol–petrol biofuels

Chargeability of ethanol–petrol biofuels during refuelling has been studied in real dispenser environment in order to assess safety risks due to fuel charging at fuel filling stations. Two biofuel blends were studied: E10 containing 10 vol-% of ethanol and 90 vol-% of petrol, and E85 containing about 85 vol-% of ethanol and 15 vol-% of petrol. Charging of standard 95 Octane petrol was studied as a reference. The results show that the charging of E85 is negligible and no charge will be accumulated as long as the fuel dispenser system is properly grounded. In the case of refuelling with E10, charge is accumulated but the level of total charge is still so low that no real electrostatic ignition hazards exist due to fuel charging at filling stations as long as the system is properly grounded. Electrostatic ignition hazards due to fuel charging are real only for standard petrol fuel.     

Accumulation of the excess of one type of charge carriers and the formation of trions in GaAs/AlGaAs shallow quantum wells

The dynamics of excitons and trions in GaAs/AlGaAs heterostructures with shallow quantum wells is studied in time-resolved photoluminescence experiments carried out with different repetition rates of picosecond pump pulses for the cases of intrawell, above-barrier, and“two-color” excitation. It is established that excess charge carriers of one type accumulated in the quantum wells under above-barrier excitation play a key role in the formation and dynamics of the exciton-trion system and determine its composition and kinetic properties. The lifetime of excess charge carriers in the quantum wells, estimated from the experimental data, exceeds 10 μs.     

A method of charge measurement for contact electrification

A method for studying contact electrification charge between different materials was developed. Physical models for the contact electrification measurement system of metal/metal, metal/insulator and insulator/insulator were proposed, where the relationships between charge and measuring potential were developed. According to the models, an electrification charge measurement system was built. As an example of using the method, contact electrification experiment between polytetrafluoroethylene (PTFE) and carbon steel plates was conducted. Comparison of the charge results by this method and Faraday cup method was made, which suggested that the current method reduced the error resulted from the charge dissipation.     

Al掺杂对HfO2俘获层可靠性影响第一性原理研究

采用基于MS(Materials Studio)软件和密度泛函理论的第一性原理方法, 研究了HfO₂ 俘获层的电荷俘获式存储器(Charge Trapping Memory, CTM)中电荷的保持特性以及耐擦写性. 在对单斜晶HfO₂中四配位氧空位(V_O4) 缺陷和V_O4 与Al替位Hf掺杂的共存缺陷体(Al+V_O4)两种超晶胞模型进行优化之后, 分别计算了其相互作用能、形成能、Bader电荷、态密度以及缺陷俘获能. 相互作用能和形成能的计算结果表明共存缺陷体中当两种缺陷之间的距离为2.216 Å时, 结构最稳定、缺陷最容易形成; 俘获能计算结果表明, 共存缺陷体为双性俘获, 且与V_O4缺陷相比, 俘获能显著增大; Bader电荷分析表明共存缺陷体更有利于电荷保持; 态密度的结果说明共存缺陷体对空穴的局域能影响较强; 计算两种模型擦写电子前后的能量变化表明共存缺陷体的耐擦写性明显得到了改善. 因此在HfO₂俘获层中可以通过加入Al杂质来改善存储器的保持特性和耐擦写性. 本文的研究可为改善CTM数据保持特性和耐擦写性提供一定的理论指导.     

Spin-dependent transport in a nanopillar non-local spin valve

We investigate the injection of a pure spin current into a non-magnetic Cu wire in a lateral spin valve. We detect the spin accumulation occurring at the interfaces between the magnetic nanopillars and the non-magnetic wire in the non-local geometry. We confirm that the accumulated spins diffuse equally in the Cu wire irrespective of the presence of a charge current. The inversion of the injector and detector magnetic nanopillars does not affect the spin signal, in agreement with analytical predictions for this system.     

Persistent currents in a lattice correlated electron ring with a magnetic impurity

The behavior of charge and spin persistent currents in an integrable lattice ring of strongly correlated electrons with a magnetic impurity is exactly studied. Our results manifest that the oscillations of charge and spin persistent currents are similar to the ones, earlier obtained for integrable continuum models with a magnetic impurity. The difference is due to two (instead of one) Fermi velocities of low-lying excitations. The form of oscillations in the ground state is “saw-tooth”-like, generic for any multi-particle coherent one-dimensional models. The integrable magnetic impurity introduces net charge and spin chiralities in the generic integrable lattice system, which determine the initial phase shifts of charge and spin persistent currents. We show that the magnitude of the charge persistent current in the generic Kondo situation does not depend on the parameters of the magnetic impurity, unlike the (magneto)resistivity of transport currents. Received 30 January 2003 / Received in final form 12 March 2003 Published online 11 April 2003 RID="a" ID="a"e-mail: zvyagin@fy.chalmers.se     

“神龙二号”气体火花开关中绝缘结构的电场分析与优化

气体火花开关作为重要部件被大量地应用于直线感应加速器和Z箍缩等大型脉冲功率装置中。绝缘结构设计不合理会使得气体火花开关中出现局部电场畸变和电荷积聚等现象。在高电压脉冲下长时间或高频次运行时,火花开关中的绝缘子会发生沿面闪络现象,直接影响到脉冲功率装置的正常运行。鉴于此,对气体火花开关中的绝缘结构进行了有限元电场分析,用表面电荷的积聚定性解释了沿面闪络发生的原因。通过对绝缘子的几何结构和电极尺寸的优化设计,有效降低了绝缘子表面和电极表面的电场强度,其中阳极三结合点场强从9.4 kV/mm降至1.5 kV/mm,阴极三结合点场强从2.95 kV/mm降至0.98 kV/mm,绝缘子表面最高场强从10.8 kV/mm降至4.95 kV/mm。优化后的绝缘结构电场分布较为合理,降低了由于表面电荷的积聚而引发沿面闪络的概率。     

Dynamics of induction charging for multiple particle agglomerations with a thin conducting surface layer

In electrostatic applications, particles are typically stacked in an arbitrary array. In this paper, multiple particle agglomerations with a finite volume conductivity, surface conductivity and permittivity have been simulated. Upon exposure to the electric field, electric shielding can occur due to the proximity of other particles, which greatly reduces the maximum accumulated charge and affects the charging time. All results have been obtained using the COMSOL commercial software. The simulation results show that shielding the electric field from a given particle reduces its saturation charge and the rate of charge accumulation was mainly affected by the volume and surface conductivities.     

p型金属氧化物半导体场效应晶体管界面态的积累对单粒子电荷共享收集的影响

由于负偏置温度不稳定性和热载流子注入,p型金属氧化物半导体场效应晶体管(pMOSFET)将在工作中不断退化,而其SiO₂/Si界面处界面态的积累是导致其退化的主要原因之一. 采用三维器件数值模拟方法,基于130 nm体硅工艺,研究了界面态的积累对相邻pMOSFET之间单粒子电荷共享收集的影响. 研究发现,随着pMOSFET SiO₂/Si界面处界面态的积累,相邻pMOSFET漏端的单粒子电荷共享收集量均减少. 还研究了界面态的积累对相邻反相器中单粒子电荷共享收集 关键词： 负偏置温度不稳定性 电荷共享收集 双极放大效应 单粒子多瞬态     

Mechanisms of fragment production in heavy-ion reactions at intermediate energies

Comparative analysis of three typical models of nuclear disintegration, the statistical multifragmentation model (SMM), the quantum statistical model (QSM) and a generalized evaporation model (GEM), is carried out. The thermodynamical properties of a decaying system as well as observable characteristics in heavy ion collisions predicted by the different models are discussed. It is shown that these models yield quite similar results for low charge yields at higher excitation energies (E/A>6 MeV per nucleon) and it is suggested that the coincidence measurements of the intermediate mass fragment multiplicity and the neutron and proton multiplicity (or alternatively, the total bound charge) may be very useful for deducing the decay mechanism. The GEM is shown to differ from the other models in predicting a high Z residue peak.     

Equivalence between the Mueller Regge model and the multiperipheral model

It is proven that a large class of pionization Mueller Regge models are equivalent to the multiperipheral model. An orthogonal similarity transformation is found which allows one to transform in either direction between equivalent multiperipheral and Mueller models. Models with charge are discussed and the problem of constructing charge conserving Mueller models is solved.     

Adiabatic pumping in a superconductor-normal-superconductor weak link

We present a formalism to study adiabatic pumping through a superconductor-normal-superconductor weak link. At zero temperature, the pumped charge is related to the Berry phase accumulated, in a pumping cycle, by the Andreev bound states. We analyze in detail the case when the normal region is short compared to the superconducting coherence length. The pumped charge turns out to be an even function of the superconducting phase difference. Hence, it can be distinguished from the charge transferred due to the standard Josephson effect.     

Investigation of MWS Relaxation in Nylon 1010 using Dielectric Relaxation Spectroscopy

Maxwell–Wagner–Sillars (MWS) relaxation in nylon 1010, arising from charge carriers accumulated at the interphase between amorphous and crystalline regions, has been investigated by means of dielectric relaxation spectra. In the frequency spectra of nylon 1010, dielectric permittivity showed high values at low frequencies originating from charge carrier movement. For the MWS relaxation, the dielectric strength was independent of temperature. The results revealed that there is a transition temperature, located between 110 and 120°C, resulting in the separation of two different charge carrier movement mechanisms. Below and above this transition temperature, the temperature dependence of the MWS relaxation time follows the Vogel–Tammann–Fulcher type, showing that the charge carrier transport is governed by the motion of the polymer chains. The change of charge carrier movement mechanisms is due to the onset of polymer chain motion in the interphase.     

The Effects of Charge Transfer Interactions on the Properties of Ice Ih

Potential models which include charge transfer are used to study ice/water coexistence properties and properties of the ice Ih phase. Two charge transfer models are used, one which is non-polarizable and one which is polarizable. These models transfer a discreet amount of charge for each hydrogen bond made and the net charge of a molecule is determined by the difference in the number of hydrogen bonds a molecule makes as a donor and as an acceptor. In ice Ih, this difference is very near zero and the net amount of charge transfer is correspondingly essentially zero. This differs from the amount of charge transfer in the liquid phase. The results for the polarizable charge transfer model confirm other studies that suggest the importance of polarizability in reproducing the high dielectric constant of ice Ih.     

Low-frequency dielectric-barrier discharge in the Townsend mode

An analytic model is proposed of a dielectric-barrier discharge in the Townsend mode, in which the space charge is small compared to the charge accumulated on the dielectric surface. The discharge mode depends substantially on the ratio between the frequency of the external voltage and the ion drift time through the gap. A low-frequency case is investigated, in which the space charge can be ignored. The analytic expressions obtained agree well with experiments and numerical simulations. The physical mechanism for the onset of relaxation oscillations in the Townsend mode is revealed. The time behavior of a dielectric-barrier discharge is qualitatively described, and its basic scaling parameters are determined.     

Absorption of solar radiation by charged water droplets

We consider the absorption of solar radiation by charge accumulated on the surface of an otherwise neutral water droplet. We estimate the order of magnitude of the additional contribution from the surface charges to the photoabsorption cross-section. The approximate location and strength of major spectral lines is indicated. This spectral information requires determination of the quantum mechanical energy levels and wave functions of the absorbing system. An approximate calculation is carried out using a simple model for electrons on the surface of the droplet. The implications for atmospheric applications are considered.