Numerical simulation on the electric charge decay of micropowder prepared by jet milling/electrostatic dispersion

Preparation of micropowder by the combination of jet milling and electrostatic dispersion is an innovative method. By means of this method, it can achieve the dual goal of producing fine powders and maintaining the dispersiveness. While, the electric charge carried by particles will vanish gradually when refined powder is stored in air, which lead to that the dispersion effect of charged particles will weaken and even disappear. In this paper, a model of electric charge decay of charged particle in air is established, the influence of particle size, relative humidity of the atmosphere, relative permittivity and initial q/m i.e. charge to mass ratio of charged micropowder on the decay process are evaluated. In addition, the non-contact measuring experiment is designed to verify the simulation results as well. The results indicate that the q/m of charged particle decreases as exponential relationship with the storage time, the remained q/m and its decay rate of particle with smaller size is lower during the whole process. The decay rate of charged powder increases with the increase of relative humidity in air. Particles with higher relative permittivity has a lower decay rate of charge, and the decay rate of particles with larger initial charge to mass ratio would also be higher. The numerical results of the model could reveal the rules in electric charge decay process well in general.     

Enhanced electrochemical properties of sodium-doped lithium-rich manganese-based cathode materials

In this work, sodium has been successfully doped into the layered lithium-rich manganese-based cathode material through melt impregnation. The as-prepared samples are characterized by multiple techniques of x-ray diffraction, scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy and the electrochemical measurements. The results show that sodium doping hardly changes the layered structure and surface morphology of pristine sample. The sample particles of sodium-doped materials exhibit polygonal shape similar to prism. The sodium-doped material possesses high rate performance and good cycling stability, and the initial charge and discharge capacity reaches 340.2 mA h g⁻¹ and 249.0 mA h g⁻¹ at a current density of 20 mA g⁻¹, respectively. The initial coulombic efficiency of the first cycle is 73 %. After running 100 repeated cycles at 40 mA g⁻¹ and 100 mA g⁻¹, the discharge capacity could still be maintained at about 230.0 mA h g⁻¹ and 220.0 mA h g⁻¹, respectively. Moreover, the voltage attenuation is effectively suppressed during charging/discharging cycles.     

地震作用下RC构件耗能能力的计算方法研究

为了优化地震作用下研究钢筋混凝土构件损伤量化的理论流程,建立合理的耗能能力计算方法,基于初始滞回阶段RC构件耗能能力衰变规律,在研究了同类型试件相等加载位移在不同滞回阶段D-n曲线形态特征的基础上,提出了后续滞回阶段耗能能力衰变模型。通过对不同滞回阶段的衰减指数进行拟合分析,提出了耗能能力计算方法中特征参数A、B、x₀、y₀的修正公式,且优化后的计算方法较优化前,其准确性和稳定性均有所提高。对于从PEER数据库选取的80个受弯破坏试件耗能估算而言,该方法同样表现出较好的准确性和适用性。     

Model for assessing organic light‐emitting diode display lifetime across applications

A model for assessing organic light‐emitting diode (OLED) display lifetime is developed and discussed for estimating OLED display lifetime in various applications. The lifetime model extends existing stretched exponential models of luminance decay for OLED devices to permit this decay to be estimated as a function of time and current density. This extended model is illustrated within an application to assess the power consumption and luminance decay of diodes within an OLED display. Various metrics of display lifetime are discussed with the aim of developing methods to assess the perceived lifetime of an OLED display to global and local luminance decay mechanisms. Finally, these metrics are applied to illustrate the performance of the model for assessing the impact of an image processing algorithm on OLED display lifetime.     

卤化银微晶体的光电子行为

卤化银乳剂微晶体的光电子行为是影响照相感光度的重要因素，本文就光电子研究方法、光电子衰减、电子陷阱、本征与外来带电中心对光电子衰减与寿命的影响以及光电子行为与其它物理性质的关系等方面加以综述．     

Photoluminescence Decay and Hydrogen Desorption of n-Type Porous Silicon

The decay under illumination of the photoluminescence (PL) intensity ofn-type porous silicon (PS) samples prepared by electrochemical etching has been investigated. We have found that the PL evolution with illumination time presents two different stages: an initial very fast decay which lasts 300 s, followedby a second one, much slower, which extends for times longer than 10⁴ s. Thisevolution suggests that two different mechanisms could be responsible for the PLintensity decay. Samples subjected to different illumination times were studied byThermal Desorption Spectroscopy (TDS). The desorption rate of H₂ and SiH_x species was monitored during linear heating of the samples. A qualitative correlationbetween the decay of the PL intensity under illumination and the amount of H₂ and SiH_x species evolved from the illuminated samples has been observed. Experimentaldata suggest that H₂ could be desorbed from the sample during the illuminationtime through a photoinduced H₂ desorption process, inducing the decrease of the PLintensity.     

The modelling and experimental study on molecular diffusion coefficient of CO2 in N-methyl pyrolidone

In this study, batchwise absorption of CO₂ in N-methyl pyrolidone (NMP) was experimentally performed at different conditions using pressure decay method, and as a result, the equilibrium data, Henry’s law constants, and kinetic data were reported. It was shown that solubility and diffusivity are two important factors affecting the kinetic behaviour of the system. This absorption system was mathematically modelled using Fick’s second law accompanied by a time-dependent boundary condition. Thus, the diffusion coefficients of CO₂ in NMP were calculated under different operating conditions by means of the experimental kinetic data. Furthermore, the influence of temperature and pressure on the diffusion coefficient of CO₂ in NMP was analysed.     

低流速下涡流二极管单向性实验研究

为研究氟盐冷却高温堆(Fluoride-salt-cooled High temperature Reactor,FHR)非能动余热排出系统的控流装置——涡流二极管在低流速下的性能参数,建立了实验装置,测试了在水工质下由3D打印尼龙材料涡流二极管的单向特性,并由实验结果得到相同结构尺寸的涡流二极管在FliBe工质下的压降值。研究结果表明,本文实验流量范围内测得的涡流二极管单向性随雷诺数的增加不断升高,最大值为23。正向流动阻力系数随雷诺数的升高不断降低,反向流动阻力系数随雷诺数的增大先增大后降低。研究结果还表明本文研究的涡流二极管结构不适用于小功率氟盐冷却高温堆非能动余热排出系统的设计。     

Characteristic Oxidation Products of Choline Plasmalogens are Detectable in Cattle and Roe Deer Spermatozoa by MALDI-TOF Mass Spectrometry

Plasmalogens (1-O-alk-1′-enyl-2-acyl-sn-glycero-3-phosphocholines and -phosphoethanolamines) are important constituents of spermatozoa membranes and possess significant antioxidative properties. This particularly holds as plasmalogens from spermatozoa also possess a very high content of highly unsaturated fatty acyl residues (especially 22:6). The organic spermatozoa extracts of two different ruminants (cattle and roe deer) were analyzed for their contents of characteristic choline plasmalogen oxidation products by matrix-assisted laser desorption and ionization time-of-flight (MALDI-TOF) mass spectrometry. It will be shown that 1-hydroxy-2-docosahexaenoyl-sn-glycero-3-phosphocholine (LPC 22:6) and formyl-LPC 22:6 are reliable measures of lipid oxidation of spermatozoa and allow, accordingly, conclusions about the storage conditions. All data on spermatozoa were also confirmed by the investigation of the oxidation behavior of selected reference compounds. It will be shown that, equally if plasmalogens or diacyl PC species are used, oxidation takes place primarily at the double bond next to the glycerol backbone. These data were additionally confirmed by recording the corresponding post source decay (PSD) fragment ion spectra.     

两种发光中心掺杂的ZnS纳米微晶研究

利用Na₂S溶液沉淀法制得了Mn²⁺及Cu²⁺掺杂的ZnS纳米微晶．用X射线衍射测定了微晶的结构及计算了晶粒尺寸．分析了量子尺寸效应造成的光学特性的变化．讨论了ZnS纳米微晶中不同类型发光中心的不同发光行为．