Glow Discharge Characteristics of Hollow Needle-Plate Electrode in Atmospheric Pressure ArgonSCIEI北大核心CSCD

Atmosphere pressure uniform plasma has the broad application prospect in the industrial field. Using hollow needle cathode - plate anode device excited by direct-current voltage, a uniform and stable glow discharge is generated at atmospheric pressure in ambient air with argon used as working gas. The influence of the experimental parameters (including gas flow rate and the gas gap width) on discharge has been investigated by optical method. It can be found that a glow-discharge plasma column can bridge the two electrodes. The plasma column is uniform, and no filaments can be discerned. Near the plate electrode, the diameter of the plasma column is largest of all positions. The maximal diameter of the plasma column increases with increasing the discharge current or the gas flow rate. Through electrical method, the voltage-current characteristic has been investigated. It has been found that the discharge voltage decreases with increasing the current which is similar with the characteristic of glow discharge in low pressure. It increases with increasing the gas gap width or the gas flow rate. By analyzing the optical emission spectrum scanning from 330 to 450 nm emitted from the direct-current glow discharge, the molecular vibrational temperature and the intensity ratio of spectral lines I-391.4/I-337.1 have been investigated as functions of the gas flow rate and gas gap width. Results indicate that both the vibrational temperature and the intensity ratio of spectral lines I-391.4/I-337.1 decrease with increasing the gas flow rate or the gas gap width. In addition, the molecular vibrational temperature and the intensity ratio of spectral lines I-391.4/I-337.1 have been investigated in spatial resolution along the direction of gas flow(plasma column axial), and give a qualitative analysis as well. It is found that the vibrational temperature and the average electron energy increase with increasing the distance from the hollow needle cathode. These results are important to the industrial applications of glow discharge.     

用瑞利激光雷达16年观测数据分析合肥地区大气密度分布特征

介绍了L625瑞利激光雷达系统结构以及基于瑞利散射理论探测大气分子数密度的原理.提出了反复迭代修正大气透过率的计算方法,并通过模拟仿真验证了该算法的可靠性.通过误差分析得到影响大气分子密度不确定度的主要因素为回波信号信噪比以及参考点处大气分子数密度值,给出了回波信号误差产生的主要来源以及参考点选取方法.最后,分析了激光雷达16年观测数据反演的结果,得到合肥地区大气分子数密度的月份以及年份分布状况,结果表明:中层大气分子数密度分布呈现明显的季节性分布特征,冬季分布稀疏,夏季分布密集,随年份分布则较为平稳.通过将统计平均得到的密度廓线与1976美国标准大气模式比对分析,发现由激光雷达观测反演得到的结果较模式值大,二者的比值在1.05～1.13之间.     

Composition of oxygen precipitates in Czochralski silicon wafers investigated by STEM with EDX/EELS and FTIR spectroscopy

In this work, we investigated the stoichiometry of oxygen precipitates in Czochralski silicon wafers. The thickness dependence of the Cliff–Lorimer sensitivity factor for the silicon/oxygen system was determined and applied for the investigation of the stoichiometry of oxygen precipitates by EDX. The results show that both plate‐like oxygen precipitates and a transitional form between plate‐like and octahedral precipi‐ tates consist of SiO₂. This was confirmed by EELS low loss spectra where the typical spectrum for amorphous SiO₂ was observed. Moreover, the absorption band of plate‐like precipitates at 1227 cm^–1 was found in the low temperature FTIR spectrum. It was demonstrated that this band can only be simulated by the dielectric constants of amorphous SiO₂. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Swift heavy ion induced capacitance and dielectric properties of Ni/n-GaAs Schottky diode

The in-situ capacitance and dielectric properties of 25 MeV C⁴⁺ ion irradiated Ni/n-GaAs Schottky barrier diode (SBD) were studied at 100 kHz in the fluence range 5 × 10¹⁰ – 5 × 10¹³ ions/cm². The investigation shows reduction in capacitance and charge density with increase in ion fluence. Consequent changes were observed in other related parameters like conductance, dielectric constant, dielectric loss, loss tangent and electrical modulus. The results were interpreted in terms of generation of swift heavy ion induced acceptor trap states by electronic energy loss mechanism. Besides, the switch over characteristics of depletion to inversion regions in the CV plot reveals minority carrier recombination centers also. The dispersion and relaxation peaks observed in bias dependent dielectric plots were ascribed to the polarization and relaxation mechanism due to the interfacial trap states. The traps and recombination centers were found to alter the barrier characteristics of the fabricated SBD depending upon the ion fluence.     

Effects of acid etching on the structure of PtNi catalyst and total exposed active sites

The integration technology of hydrogen preparation–hydrogen storage not only can utilize hydrogen energy efficiently but also can improve the selectivity of the electrode maximally. In the present work, the structure and composition of the PtNi catalyst was characterized by X-ray diffraction (XRD); and its electrochemical properties, morphology, and surface binding energy were analyzed by cyclic voltammetry (CV) and linear scanning voltammetry (LSV), scanning electron microscopy equipped with energy-dispersive spectrometry (SEM-EDS), and X-ray photoelectron spectroscopy (XPS), respectively. The effects of different acid etching treatments (e.g., etching time, etchant concentration, and etching temperature) on the structure and surface active sites were investigated by the orthogonal experiment. The experimental results reveal that after etching with 0.5 mol/L of perchloric acid for 0.5 h at 60°C, the electrode weight loss of the PtNi catalyst is mainly attributed to the large loss of Ni atoms in film layer. This results in the reduced alloy phase in film layer and the appearance of Pt characteristic diffraction peak. The relative content of Pt on the surface of the film electrode increases significantly, and the total number of active sites also increases correspondingly. The binding energy of Pt4f_7/2 decreases by 0.19 eV, and the number of active sites involved in hydrogen release decreases, indicative of the reduced promotion effect of the PtNi catalyst on hydrogen release.     

基于高阶累计量的大气光通信自适应信号处理

针对强湍流信道下信号衰落的特点,分析了对数正态分布模型与K分布模型的适用范围.基于K分布模型建立大气光通信接收信号模型,并给出了自适应最优门限检测方法.采用四阶和六阶累计量对强湍流信道参量进行估计,采用二阶累计量对其它高斯噪音进行估计,得到K分布参量及高斯噪音统计量的预测值,实现自适应门限更新.基于Monte Calro算法进行仿真,给出了门限更新算法对通信系统误码率的影响,同时分析了信号采样率对估计参量偏差的影响.计算表明,在强湍流情况下,大气光通信系统的误码率性能得到极大的改善,优于基于MLSD检测的接收机.     

Anti-Hair Loss Effect of Adenosine Is Exerted by cAMP Mediated Wnt/β-Catenin Pathway Stimulation via Modulation of Gsk3β Activity in Cultured Human Dermal Papilla Cells

In the present study, we investigated the molecular mechanisms of adenosine for its hair growth promoting effect. Adenosine stimulated the Wnt/β-catenin pathway by modulating the activity of Gsk3β in cultured human dermal papilla cells. It also activated adenosine receptor signaling, increasing intracellular cAMP level, and subsequently stimulating the cAMP mediated cellular energy metabolism. The phosphorylation of CREB, mTOR, and GSK3β was increased. Furthermore, the expression of β-catenin target genes such as Axin2, Lef1, and growth factors (bFGF, FGF7, IGF-1) was also enhanced. The inhibitor study data conducted in Wnt reporter cells and in cultured human dermal papilla cells demonstrated that adenosine stimulates Wnt/β-catenin signaling through the activation of the adenosine receptor and Gsk3β plays a critical role in transmitting the signals from the adenosine receptor to β-catenin, possibly via the Gαs/cAMP/PKA/mTOR signaling cascade.     

医疗保险索赔数据的广义Pareto分布拟合

How to choose an optimal threshold is a key problemin the generalized Pareto distribution (GPD) model.This paper attains the exactthreshold by testing for GPD,and shows that GPD model allows the actuary to easily estimate high quantiles and the probable maximum loss from the medical insurance claims data.     

Tire and soil effects on power loss: Measurement and comparison with finite element model results

In the present study, the effect of vertical load, tire inflation pressure and soil moisture content on power loss in tire under controlled soil bin conditions were investigated. Also a finite element model of tire-soil interaction in order to achieve a suitable model for predicting power loss in tire was created. Increasing the vertical load on the tire had a noteworthy impact on increasing the tire contact volume with the soil, reducing the percentage of slip, and increasing the rolling resistance; although, reducing the load on the tire had the opposite effect. At a constant inflation pressure, by increasing the vertical load on the tire, the amount of power loss due to the rolling resistance and the total power loss in the tire increased. Increase in soil moisture content increased the power loss caused by slip. Increasing the inflation pressure at a constant vertical load, also increasing the soil moisture content, led to an increase in the power loss caused by rolling resistance, and increase total power loss. The obtained error for estimating power loss of rolling resistance and total power loss was satisfactory and confirmed the acceptability of the model for power loss estimation.     

交变电场作用下骨表面温升的实验研究

骨具有力电性质,这一性质可促进骨组织生长。骨既是生理器官又是介电材料,在交变电场作用下,其表现行为可能有生理作用。为此,本文测量了骨悬臂梁试样在交变电场下的表面温升与顶端挠度。发现在电压70V,频率为10~70kHz的交流电场下,最大表面温升达到2~4℃,最大挠度变化为9.0~78.7μm;在频率10kHz,电压为70~175V的交流电场下,最大表面温升达到4~6℃,最大挠度变化为13.0~114.3μm。同时测量了两种经典介电材料有机玻璃和聚乙烯在交变电场下的温升与顶端挠度,最大温升低于0.5℃,但是挠度与骨试样相当,所以相对高温升是骨特有的性质。将交流电压有效值替换成相同幅值的直流电压时,最大温升也低于0.5℃,基本没有挠度变化,所以相对的高温升反映了骨的交流性质。分析后认为,骨在交变电场作用下的温升由胶原的介电损耗引起。实验数据显示,骨在交变电场下,表面温度变化与加载电压的平方成正比,且在实验加载的10~70kHz频段内,骨的介电常数随频率的变化明显。