工业以太网网络故障的应对实践

为了应对工业以太网在使用过程中频繁发生网络故障的现象,利用对网络节点重新规划分配、减小通讯量、减轻网络传输负担,选用高质量的网络传输介质、对网络外界杂波干扰进行屏蔽的方法,对原有的工业以太网络进行大幅改进,经过统计,月平均故障报警次数由改进前的28次变为改进后的2次,网络故障的发生频次得到明显降低.因此,以上改进方法可有效应对工业以太网使用过程中最为常见的网络故障问题,起到极大减少或根除以太网网络故障的作用.     

Electrochemical performance of MCMB/(AC+LiFePO4) lithium-ion capacitors

Lithium-ion capacitors(LICs) were fabricated using mesocarbon microbeads(MCMB) as a negative electrode and a mixture of activated carbon(AC) and LiFePO4 as a positive electrode(abbreviated as LAC).The phase structure and morphology of LAC samples were characterized by X-ray diffraction(XRD) and field emission scanning electron microscopy(FESEM).The electrochemical performance of the LICs was studied using cyclic voltammetry,charge-discharge rate measurements,and cycle performance testing.A LIC with 30 wt% LiFePO4 was found to have the best electrochemical performance with a specific energy density of 69.02 W h kg-1 remaining at 4 C rate after 100 cycles.Compared with an AC-only positive electrode system,the ratio of practical capacity to theoretical calculated capacity of the LICs was enhanced from 42.22% to 56.59%.It was proved that adding LiFePO4 to AC electrodes not only increased the capacity of the positive electrode,but also improved the electrochemical performances of the whole LICs via Li+ pre-doping.     

复合分位数下的国债利率期限结构研究

本文采用复合分位数回归(CQR)的估计方法对利率期限结构模型贴现率的估计与预报进行研究。实证结果表明,在小样本情形下复合分位数回归方法要比最小二乘法和分位数回归法稳健性更强,表现出对参数.     

基于AHP的贝叶斯网络故障诊断方法研究

针对基于专家知识的故障诊断方法依赖经验的局限,提出一种基于层次分析法（AHP）的贝叶斯网络化工过程故障诊断方法。通过基于关联函数的AHP得到所有变量的权值,对22个变量节点的权值进行排序并将该排序作为K2算法的学习输入建立贝叶斯网络模型,同时结合复杂网络分析指标进行化工过程的故障诊断。通过TE过程故障诊断实例证明本文方法不仅避免了K2算法专家知识的主观因素影响,同时能很好地进行故障定位,找到故障源。     

基于半参数部分线性混合效应模型的房地产上市公司盈利能力影响因素研究

基于沪深两市的50家房地产上市公司2006年至2015年期间的纵向数据,从资产结构、负债结构、公司规模、公司风险、发展潜力5个方面分析了影响房地产上市公司盈利能力的因素。通过建立净资产收益率、流动资产率、资产负债率、总资产的对数、主营业务收入的对数5个观测变量的半参数部分线性混合效应模型进行实证分析,并根据贝叶斯推断给出了模型参数的估计值,最后通过将实证模拟结果与房地产行业上市公司的实际情况进行对比分析,证明了所建模型的有效性。     

Optical wavefront distortion due to supersonic flow fields

The optical wavefront distortion caused by a supersonic flow field around a half model of blunt nose cone was studied in a wind tunnel. A Shack-Hartmann wavefront sensor was used to measure the distorted optical wavefront. Interesting optical parameters including the peak variation (PV), root of mean square (RMS) and Strehl ratio were obtained under different test conditions during the experiment. During the establishing process of the flow field in the wind tunnel test section, the wavefront shape was unstable. However after the flow field reached the steady flow state, the wavefront shape kept stable, and the relative error of wavefront aberration was found small. The Shack-Hartmann wavefront sensor developed was proved to be credible in measuring quantitatively the optical phase change of light traveling through the flow field around model window.     

Detrital zircon of 4.1 Ga in South China

One hadean zircon from the Cambrian sandstone in the southern part of South China has a U-Pb age of 4107±29 Ma with ε Hf(t) value similar to that of the homochronous depleted mantle and Hf model age of 4102±21 Ma.This demonstrates the existence of hadean crustal remnant in South China.A close match between the U-Pb age and Hf model age with the highly position ε Hf(t) value indicates the growth and immediate reworking of juvenile crust from the depleted mantle at ca 4.1 Ga.The prominent "Pan-African" and Grenville zircons derived from the exotic sources were also found in the sample,which indicates a linking between South China and Gondwana in the Cambrian period.The southern part of South China has complex histories of crustal growth and tectonic evolution.     

Surface-enhanced Raman scattering on dual-layer metallic grating structures

Dual-layer Metallic grating (DMG) structures as surface-enhanced Raman scattering (SERS) substrates are studied using ben-zenethiol as the probe analyte. The DMG structure consists of a SiO₂ grating and 100-nm-thick gold coating layers. An enhancement factor of 10⁵ is achieved by optimizing the SiO₂ grating height within the range from 165 to 550 nm. The enhancement factor dependence on the SiO₂ grating height is due to the surface plasmon excitation, which is dependent on the polarization of the incident light, and confirmed by finite difference time domain simulations. This study demonstrates the advantages of high uniformity, reproducibility and sensitivity in the DMG structures for SERS applications.     

随机激励van der Pol-Duffing方程三峰P-分岔

本文讨论三稳态van der Pol-Duffing振子的随机P-分岔问题及参数影响．首先由随机平均法导出振动幅值的稳态概率密度函数,再应用突变理论得到系统发生随机P-分岔的临界参数条件．结果表明：参数变化时,系统经两次随机P一分岔,幅值稳态概率密度分布曲线峰的个数从1增加到3．随机激励的强度、系统阻尼系数对概率密度分布有重要影响,概率密度曲线峰的最大数目与确定性系统吸弓l子的数目相等．     

一种微波等离子体反应器的优化设计

采用HFSS软件对点火腔和反应腔进行优化仿真,得出了最优尺寸的腔体。点火腔设计为压缩弯波导形状,在谐振情况,单位微波功率可产生高达1.35×104V/m的微波场强,便于产生等离子体;反应腔设计为同轴谐振腔结构,谐振情况下S11散射系数为-54,可产生较大面积的等离子体并提高了微波能量的利用率;反应腔中的石英反应管设计为螺旋结构,可延长等离子体在反应腔中的反应时间,从而提高等离子体化学反应的转化率;通过电调反射器及环行器系统来自由调节点火腔和反应腔中微波能量的分配,实现反应器等离子体点火、加热于一体的功能。