关于6维近凯勒流形中二阶平行拉格朗日子流形的注记

证明6维严格近凯勒流形中的二阶平行拉格朗日子流形一定是全测地的,这推广了L.Vrancken等人文中的一个重要结果.特别地,得到了齐性近凯勒S³×S³中该类拉格朗日子流形的完全分类.     

PPP项目国有企业隧道行为研究

PPP项目中, 国有企业时常利用控制权优势和信息不对称实施隧道行为, 加大了民营资本进入PPP项目的阻力, 损害了项目整体利益, 不利于PPP模式的健康可持续发展。本文在分析PPP项目中国企隧道行为表现形式和形成机理的基础上, 分别通过博弈论和投资组合模型构建了隧道行为实施条件和发生概率模型。研究结果表明, 国企实施隧道行为需具备基于控制权的先决条件, 挖掘成本相对项目利益的比重越大, 所需控制权越高; 而隧道行为的发生概率随着挖掘成本的降低和控制权的增加而增加。通过蒙特卡洛模拟对河北承德市双峰寺水库PPP项目进行案例分析, 验证了国企隧道行为实施条件和概率模型的可行性和适用性。最终, 分别从提高民企的谈判能力, 增加PPP项目信息透明度, 加强政府监管, 并使国企和项目整体产生利益协同四个方面提出隧道行为治理机制, 保障PPP模式的可持续发展。     

基于COMSOL的纳米傅里叶红外光谱系统数值模型

傅里叶红外光谱（FTIR）是材料表征的一种重要手段,然而受限于光的衍射极限,传统傅里叶红外光谱仪的极限空间分辨率在微米量级,无法应用于纳米材料的表征。纳米傅里叶红外光谱（Nano-FTIR）是一种新兴的超分辨光谱表面分析技术,其以纳米级空间分辨率、宽光谱范围和高化学灵敏性的特点在纳米材料表征研究中展现了巨大的潜力。定性及定量的研究Nano-FTIR信号高空间分辨的来源和系统中光谱信号的提取过程,可以为Nano-FTIR仪器的设计研发和样品光谱表征结果的解释提供重要依据。该研究从典型的仪器结构和基本的工作原理出发,在多物理场有限元分析软件COMSOL中建立了等效研究模型,并对模型的重要细节和数值计算过程分别进行了说明。在仿真研究中,首先基于麦克斯韦电磁波理论计算了模型空间的电磁场增强情况,再模拟了探针在介电常数差异巨大的两种材料交界处的“线扫”过程,探讨了针尖近场增强信号的空间分辨率。随后,以探针与样品的散射功率为数值模型的研究对象,仿真了探针“轻拍”对信号的调制和解调提取的过程,并讨论了不同入射倾角和解调频率对光谱信号提取的影响。最后,为了验证模型的合理性,仿真了20,100和300 nm三种厚度SiO₂薄膜样品在900～1 250 cm-1波数范围的光谱响应,并将仿真得到的光谱与实测结果进行了对比。结果表明随着样品厚度的增厚,光谱信号得到相应的增强,模型预测的谱图与实测谱图波形与波峰位置较为一致,且与以往一些文献中采用针尖-样品间电场强度表示针尖处散射信号强弱的方法相比,获得的谱图在峰形上更为接近。提出的数值模型可用于Nano-FTIR光谱的预测,此外,模型也具有一定的通用性,可以为其他基于散射型近场光学显微（s-SNOM）技术的太赫兹光谱技术和针尖增强拉曼光谱研究提供一定的借鉴。     

深海富钴结核微区X射线荧光光谱分析和数据挖掘

西太平洋富钴结核是近年来新发现的海底固体矿产资源,富含Mn,Fe,Co,Ni和Cu等多种关键金属元素。富钴结核是一种非均质的地球化学和矿物学集合体,粒径约6 cm的结核在生长过程中记录了数千万年的海洋沉积历史,亟需高分辨率的分析技术揭示古海洋环境信息。采用微区X射线荧光光谱仪（μ-XRF）,对C3BC1704富钴结核开展多元素面扫描,获得了原位高分辨率多元素的信号强度数据,评价了μ-XRF技术在富钴结核中的应用质量。元素信号谱峰特征和数据频谱分布结果显示,富钴结核中Mn,Fe,Ti,Co,Ca和Ni等元素信号强度敏感,数据呈现相对较好的正态分布特征,可用于定量或半定量分析;Si,Cu和Al等元素信号较弱,数据呈现左偏的正态分布特征,建议相关数据仅作参考。μ-XRF获得的数据量庞大且彼此独立,本研究将不同元素连接成彼此关联的多维矩阵,实现了数据的位置信息和特征元素之间的数学运算和筛选,了解了金属元素的分布和变化特征,揭示了富钴结核生长过程的环境变化。结果显示,Mn和Fe等元素在生长层中波动剧烈,金属元素在富钴结核中的分布极不均匀,显示出多成因类型的交替微层和7个大的生长周期旋回。C3BC1704富钴结核主体暴露在海水中,金属元素主要来自海水,化学组成指示为典型的水成成因。进一步定量分析结果显示,Mn,Cu和Ni等元素含量从内部向外围呈现同步降低的趋势,Fe,Ti和Co等元素含量则呈现同步升高的趋势,这些特征指示早期偏向于成岩富集环境,晚期则以水成富集为主。富钴结核金属元素的分布和变化特征,清晰呈现了富钴结核的生长结构,揭示了富钴结核生长过程的环境变化,有利于富钴结核的成矿模型的构建。     

Effect of system parameters on the size distributions of hollow nickel microspheres produced by an ultrasound-aided electrical discharge machining process

Ultrasound-aided electric discharge machining（EDM） is an emerging technology for producing hollow nickel microspheres.This technology combines traditional EDM with the cavitation and vibration effects of ultrasound to produce hollow microspheres.In this paper,ultrasound-aided EDM was carried out in a kerosene medium（the working solution）.The effects of various parameters on the sizes of microspheres were investigated using scanning electronic microscopy（SEM）.Smileview software was used to measure the sizes of the microspheres.Originpro software was used for statistical analysis to determine the size distributions of the microspheres.To study the effects of the system parameters on the sizes of the microspheres,we first investigated the necessity of using an ultrasonic wave with EDM.After comparing the experimental results with and without the ultrasonic field,we found that ultrasound-induced cavitation and vibration effects reduced the diameters of the microspheres.We then studied the effects of several electrical parameters,including the arc current,pulse width,and gap voltage,on the sizes of the microspheres at an ultrasound frequency of 40 kHz.Smaller microspheres could be obtained by lowering the arc current,pulse width,and gap voltage.     

A mild one-step solvothermal route to truncated octahedral magnetite crystals

Perfect truncated octahedral magnetite crystals were successfully synthesized from FeCl_3·6H_2O and poly(acrylic acid)(PAA)in an alkaline ethylene glycol solution via a mild one-step solvothermal process.The structure and morphologies of the obtained products were characterized by powder X-ray diffraction(XRD),Raman spectroscopy,scanning electron microscopy(SEM),and transmission electron microscopy(TEM).The effects of synthetic parameters including reaction temperature,reaction time,and the amount of alkali on the morphological evolution of the truncated octahedral magnetite crystals were systematically explored.160℃ was found to be the optimum temperature for the formation of truncated octahedral magnetite crystals.Below 160 ℃,little magnetite was formed.Above 160 ℃,the truncated octahedrons were gradually transformed into irregular-shaped polyhedrons.Alkali is indispensable in promoting the formation of magnetite at mild temperatures.The truncated octahedral magnetite crystals were found to be ferromagnetic and had a saturation magnetization of about 83 emu/g.     

基底温度对α-C:H膜微观结构的影响

使用RF-PECVD法分别在基底温度为60℃、120℃和200℃的N型单晶锗表面制备了α-C:H膜,采用拉曼光谱、傅里叶变换红外吸收光谱和原子力显微镜等技术手段研究分析了α-C:H膜的价键组成及表面形貌,讨论了基底温度对α-C:H膜微结构及部分性能的影响。结果表明,在α-C:H膜沉积过程中,基底温度对膜层微观结构有较大影响,基底温度60℃时,膜层表面光滑、致密无石墨化现象。随着基底温度的升高,α-C:H膜中含H量和微晶石墨量逐渐增多,α-C:H膜层性能也逐步退化。     

Strong perpendicular magnetic anisotropy in Co2FeAl0.5Si0.5 film sandwiched by MgO layers

Co2FeAl0.5Si0.5 (CFAS)-based multilayers sandwiched by MgO layers have been deposited and annealed at different temperatures. Perpendicular magnetic anisotropy (PMA) with the magnetic anisotropy energy density Ku ≈2.5×106 erg/cm3 (1 erg = 10-7 J) and the coercivity Hc = 363 Oe (1 Oe = 79.9775 A · m-1) has been achieved in the Si/SiO2/MgO (1.5 nm)/CFAS (2.5 nm)/MgO (0.8 nm)/Pt (5 nm) film annealed at 300 ℃. The strong PMA is mainly due to the top MgO layer. The structure can be used as top magnetic electrodes in half-metallic perpendicular magnetic tunnel junctions.     

Tunneling effect in cavity-resonator-coupled arrays

The quantum tunneling effect (QTE) in a cavity-resonator-coupled (CRC) array was analytically and numerically investigated. The underlying mechanism was interpreted by treating electromagnetic waves as photons, and then was generalized to acoustic waves and matter waves. It is indicated that for the three kinds of waves, the QTE can be excited by cavity resonance in a CRC array, resulting in sub-wavelength transparency through the narrow splits between cavities. This opens up opportunities for designing new types of crystals based on CRC arrays, which may find potential applications such as quantum devices, micro-optic transmission, and acoustic manipulation.