Mössbauer studies of illites and heat-treated illite as related to coal-conversion processes

Mossbauer spectra of iron species in the following illites were studied: Grundite, Fithian, Minerva, and New Albany. Spectra of samples of Fithian illite heated at temperatures of 225, 700, and 1000 °C were also obtained. Analyses of these spectra provide Mössbauer parameter values of iron species in the illites and heat-transformed illite for comparison with similar species found in coals containing illites and in coal process residues derived from them. The illites contain both ferric and ferrous species. Mössbauer parameters for one of the ferric species, designated M(2), are virtually the same as those of pyrite. The two species are therefore difficult to distinguish from one another. Values of the concentration of pyrite in coals and shales may be inflated if the pyrite concentration is measured by Mössbauer spectroscopy. Mössbauer spectra of the heat-treated illite samples reveal changes in iron distribution, principally at the 700 and 1000 °C levels, where there are found three and six different iron species respectively. These changes are accompanied by reduction of ferric to ferrous iron. This process should be integrated into any assessment of the iron chemistry which accompanies coal-conversion processes.     

基于云模型的基本概率赋值生成方法及应用

针对证据理论应用中基本概率赋值(BPA)生成模型难以确定问题,该文提出一种基于云模型的BPA生成方法。首先基于样本属性的正态云模型构建单子集命题的BPA模型函数,并将复合子集的模型函数表示为高斯函数乘积融合。其次提出一种根据测试样本动态度量属性权重的方法来兼顾信息源的可靠性。最后,用属性权重修正模型函数输出的结果得到BPA。鸢尾花等数据集分类识别实验表明,该方法识别准确性高,且适用于样本较少的情况。     

基于单通道多尺度图神经网络的自动调制识别

针对自适应可见性图(AVG)算法复杂度过高且精度提升不明显的缺点,该文提出一种基于单通道多尺度图神经网络(SMGNN)的自动调制识别(AMR)框架,并对框架各个部分进行了可解释性研究。首先利用多层感知机和1维卷积自适应地实现了单通道信号序列和图之间的映射,有效降低了AVG算法的复杂度;其次,设计了一种多尺度图神经网络,将不同分辨率的特征进行融合,提升了模型识别准确率。实验表明,该文提出的SMGNN算法相比于AVG算法节省了近1/2的参数量,且识别精度得到了较大的提升。     

基于周期截断数据矩阵奇异值分解的干扰抑制技术

针对现有适用于单天线接收机的干扰抑制技术难以为周期调频(PFM)干扰和卫星导航信号提供足够分离度,导致消除干扰成分时卫星导航信号损伤较大的问题,该文提出一种基于周期截断数据矩阵奇异值分解的干扰抑制方法。利用调频干扰信号的周期性把分散在较大带宽的能量集中到重排数据中几个甚至单个频点;进而采用奇异值分解(SVD)将干扰与期望信号映射进不同的投影子空间以消除干扰成分。仿真结果表明该方法可以降低在剔除干扰时卫星导航信号损失,提升卫星导航接收机对抗宽带周期调频干扰的能力。     

Experimental investigation of the dynamic behavior of railway track with sleeper voids

Railway Engineering Science - The deterioration of the sleeper support on the ballasted track begins with the accumulation of sleeper voids. The increased dynamic loading in the voided zone and the...     

Dielectric and thermal studies of segmental dynamics in silica/PDMS and silica/titania/PDMS nanocomposites

Effects of silica and silica/titania nanoparticles on glass transition and segmental dynamics of poly(dimethylsiloxane) (PDMS) were studied for composites of a core–shell type using differential scanning calorimetry, thermally stimulated depolarization current, and dielectric relaxation spectroscopy techniques. Strong interactions between the filler and the polymer suppress crystallinity (T_c, X_c) and affect significantly the evolution of the glass transition in the nanocomposites. The segmental relaxation associated with the glass transition consists of three contributions, arising, in the order of decreasing mobility, from the bulk (unaffected) amorphous polymer fraction (α relaxation), from polymer chains restricted between condensed crystal regions (α_c relaxation), and from the semi‐bound polymers in an interfacial layer with strongly reduced mobility due to interactions with surface hydroxyls of silica and silica/titania nanoparticles (α′ relaxation). The evolution of surface affected CH₃ groups, as well as the degree of interaction of PDMS molecules with surface hydroxyl groups as a function of treatment temperature, was assessed by Fourier transform infrared spectroscopy, thermogravimetry and differential thermal analysis. The effectiveness of silica/PDMS and silica/titania/PDMS nanocomposites as hydrophobic coatings was investigated by static contact angle measurements. It was shown that the presence of titania nanoparticles and adsorbed PDMS promotes the hydrophobic properties of the PDMS coating after treatment in the 80–650°C range. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41154.     

High-Temperature Oxidation of Bismuth- and Antimony-Based Sulfosalts

In this article, oxidation processes of Ag-Bi-Sb-based phases were investigated. Synthesized AgBiS₂ and AgSbS₂-Sb₂S₃-Sb samples were thermally analyzed in synthetic air by applying the simultaneous DSC-TGA analysis technique. The oxidation processes at P_O?=0.2 atm and T<1173 K were observed to take place in many-step sequence of various reactions with an overall reaction 2AgMeS₂ + 5.5O₂(g) ? 2Ag + Me₂O₃ + 4SO₂(g), where Me=(Bi,Sb). Oxidations of AgBiS₂, Sb₂S₃, and AgSbS₂ were observed to begin above 549±2K, 610±2K, and 733±2K, respectively. Furthermore, oxidation processes of AgBi₃S₅ and Ag₃SbS₃ were estimated, and thermodynamic functions for the overall oxidation reactions were calculated and discussed.     

基于BP神经网络算法的Ti-6Al-4V激光NiAl-VC合金化的工艺研究

为了进一步提高Ti-6Al-4V的性能,以满足其在工程中更广泛的运用,研究了在Ti-6Al-4V激光NiAl-VC合金化的工艺。以改变激光功率、激光扫描速度和粉末质量含量比例进行了工艺实验,采用BP神经网络(BP-NN)算法,建立了合金化层性能与工艺参数之间的关系模型,并通过验证实验表明预测效果良好,具有可行性。采用BP-NN算法进行了模拟实验,分析了不同工艺参数条件对合金化层深度、宽度、平均硬度、最高硬度的影响规律。本研究对Ti-6Al-4V激光NiAl-VC合金化的实践应用具有指导意义和参考价值。     

Photoelastic and acousto-optical properties of Cs2HgCl4 crystals

We use a Mach-Zehdner interferometric technique to study the piezo-optical properties of Cs2HgCl4 crystals at room temperature. All piezo-optical (pi(mn)) and photoelastic (p(in)) tensor constants are obtained. A substantial photoelastic effect and low ultrasonic velocities in these crystals determine a relatively high figure of merit M2 for isotropic diffraction (for a certain geometry of acousto-optical interactions, M2 approximately 110 x 10(-15) s3/kg). The new material may be considered, therefore, a candidate for applications in acousto-optical devices. The dependence of the acoustic walk-off angle on the direction of sound propagation is calculated for the principal crystallographic planes.