广义逆矩阵在OFDM系统信道估计中的应用

介绍了矩阵知识在计算卷积中的应用、广义逆矩阵的概念以及应用广义逆矩阵在OFDM系统中进行时域信道估计的方法,并对此方法进行了仿真。在仿真结果的基础上对时域信道估计方法和频域信道估计方法作了定性的评估。总结了广义逆矩阵进行时域信道估计的优缺点。     

Understanding interfacial behaviors of isobutane alkylation with C4 olefin catalyzed by sulfuric acid or ionic liquids

The interfacial properties between the hydrocarbon phase including isobutane and 2‐butene and the catalyst phase including H₂SO₄ or ionic liquids (ILs) with various alkyl chain length on their imidazolium cations have been investigated using molecular dynamics (MD) simulations. Compared to H₂SO₄, ILs can obviously improve the interfacial width, solubility and diffusion of reactants at the interface. The ILs with longer chains on cations exhibit a significant density enrichment of alkyl chains at the interface and tend to orient themselves with alkyl chains perpendicular to the interface and protruding into the reactant phase, which is in good agreement with the van der Waals energy between the reactants and cations of the ILs. The ILs with longer chains can improve the interfacial width and facilitate the dissolution of isobutane in catalyst phase, and thus exhibit a better catalytic performance, which agrees well with alkylation experiments in this work. © 2017 American Institute of Chemical Engineers AIChE J, 64: 950–960, 2018     

Opposite effects of self-growth amorphous carbon and carbon nanotubes on the reforming of toluene with Ni/α-Al2O3 for hydrogen production

Ni-based catalysts are prone to be deactivated by carbon deposition. This study aims to investigate the influence mechanism of different types of carbon deposition on the activity of Ni/α-Al₂O₃ catalyst at various steam-to-carbon (S/C) ratios during steam reforming of toluene for hydrogen production. At a low S/C ratio of 1, the catalytic activity of Ni/α-Al₂O₃ was inhibited due to the covering and blocking of Ni active sites by the formation of amorphous carbon on the Ni surface. While at a high S/C ratio of 3, more than 80 wt% of carbon deposition was found to be self-growth carbon nanotubes (CNTs) with an average diameter of around 15 nm. The activity of Ni/α-Al₂O₃ in steam reforming of toluene was unusually promoted, which can be attributed to the tip-growth mechanism of CNTs, whereby the Ni particles migrated to the tip or the surface of CNTs, resulting in the improved active site dispersion.     

双子表面活性剂12-4-12最佳合成条件的研究

以N,N-二甲基十二烷基叔胺与1,4-丁二醇为原料两步合成季铵盐型双子表面活性剂12-4-12,通过单因素法确定N,N-二甲基十二烷基叔胺与1,4-二溴丁烷的最佳反应条件。双子表面活性剂12-4-12的最佳合成条件为:反应物摩尔比为n(N,N-二甲基十二烷基叔胺)∶n(1,4-二溴丁烷)=2.2∶1,溶剂为异丙醇,反应温度82℃,反应时间12 h,产率为95.8%。     

Study on the long-term behaviour of glass fibre in the tensile stress field

Glass fibre is a random network structure composed of [SiO₄] tetrahedra. The structure contains a large number of defects, which act as crack initiation points. Under tensile stress, cracks undergo crack initiation, stable propagation, failure propagation, and fracture, and the stress that begins after unstable propagation is called the critical fracture stress. When the stress is less than the critical value, the crack is subject to the force of chemical bonds during the crack propagation process, and crack arrest occurs. When the stress is greater than the critical value, the glass fibre will undergo destructive fracture. In this paper, long-term tensile tests were carried out on glass fibre and a glass fibre composite under different constant tensile stress conditions. The fracture times of the glass fibre and glass fibre composite under different tensile stresses were obtained, the critical fracture stress of glass fibre was inferred, and the fracture mechanism was explained.     

A blind dual color images watermarking based on quaternion singular value decomposition

Multimedia Tools and Applications - With the rapid development of the Internet, the color digital image copyright protection is facing severe challenges. Simultaneously, the color digital images...     

区域地质图图例系统库调用方法与应用研究

为合理解决MapGIS系统库与国家标准之间的有效衔接,提高实际应用效率,以《区域地质图图例》国家标准为基础,从规范的研究现状、系统库的调用方法以及实际应用等3个方面,介绍了如何将现行标准、系统库与应用系统紧密结合,重点解决了三者之间的应用衔接问题。研究成果不仅对于优化系统库的应用方式及提高系统库的应用效率具有实际意义,而且对于地理信息系统的升级完善和系统库的补充完善均具有重要指导意义。     

勘探工程数字化地质编录现状分析与解决方案

通过对MicroMine 勘探软件、SD 储量计算软件、数字固体矿产勘查系统等现有地勘专业应用软件的应用现状、软件特点、数据特点进行分析,指出MicroMine 和SD 软件主要用于矿体建模、储量计算、矿山设计和自动成图等方面,而数字固体矿产勘查系统对勘探工程数据采集的实现方法和采集效率难以满足用户的实际。文章结合野外地质工作实践,从数据模型、数据标准、编录原理、编录步骤等几个方面阐述了如何实现勘探工程数字化地质编录。数据模型和数据标准的建立,不仅优化了勘探工程原始地质编录数据的组织,而且方便了用户对原始地质编录数据的后续开发利用。数字化地质编录理论和方法的提出,不仅科学合理、符合实际,而且对软件的实现具有重要指导意义。     

Electrochemical performances of spinel oxides as cathodes for intermediate temperature solid oxide fuel cells

The spinel-type oxides of (Mn, Co, Cu)₃O₄ prepared via a citric–EDTA acid process were investigated as candidate cathodes of intermediate temperature solid oxide fuel cells (IT-SOFCs). (Mn, Co)₃O₄ spinel oxide shows a phase transition from tetragonal to cubic when the doping amount of cobalt element increases. Their electric conductivities increase with the cobalt content and are enough high for them used as cathodes of IT-SOFCs. A fuel cell with (Mn, Co)₃O₄ spinel cathode was successfully evaluated based on YSZ electrolyte. (Mn, Co)₃O₄ spinel cathodes show good electrochemical activities, demonstrating the feasibility of the spinel oxide being a cathode of IT-SOFC. As copper doped into (Mn, Co)₃O₄ spinel, the P_peak for Cu_0.5MnCo_1.5O₄ cathode rise to 343, 474 and 506 mW cm⁻² at 700, 750 and 800 °C, respectively. The results reveal that the spinel-type oxides are promising cathodes for IT-SOFCs, especially for Cu_0.5MnCo_1.5O₄.