Structure and crystallization behavior of complex mold flux glasses in the system CaO-Na2O-Li2O-CaF2-B2O3-SiO2: A multi-nuclear NMR spectroscopic study

The structure of mold flux glasses in the system CaO-(Na,Li)₂O-SiO₂-CaF₂ with unusually high modifier contents, stabilized by the addition of ∼4 mol% B₂O₃, is studied using ⁷Li, ²³Na, ¹⁹F, ¹¹B, and ²⁹Si magic-angle-spinning (MAS), and ⁷Li{¹⁹F} and ²³Na{¹⁹F} rotational echo double-resonance (REDOR) nuclear magnetic resonance (NMR) spectroscopy. When taken together, the spectroscopic results indicate that the structure of these glasses consists primarily of dimeric [Si₂O₇]⁻⁶ units that are linked to the (Ca,Na,Li)-O coordination polyhedra, and are interspersed with chains of corner-shared BO₃ units. The F atoms in the structure are exclusively bonded to Ca atoms, forming Ca(O,F)_n coordination polyhedra. This structural scenario is shown to be consistent with the crystallization of cuspidine (3CaO·2SiO₂·CaF₂) from the parent melts on slow supercooling. The progressive addition of Li to a Na-containing base composition results in a corresponding increase in the undercooling required for the nucleation of cuspidine in the melt, which is attributed to the frustrated local structure caused by the mixing of alkali ions.     

Preparation,structure and microwave dielectric properties of novel La2MgGeO6 ceramics with hexagonal structure and adjustment of its τf value

A novel La₂MgGeO₆ ceramic was synthesized through a solid-state reaction process within a sintering temperature range of 1450–1550 °C. By a combination of X-ray diffraction and Rietveld refinement analyses, the ceramics were found to have a pure hexagonal phase structure belonging to space group R3/146. The scanning electron microscopy images revealed that the ceramic grains were closely connected. The effects of internal (lattice energy, valence bond, and fraction packing) and external factors (density) on the microwave properties of ceramics were also studied. The ceramic exhibited excellent microwave dielectric performances, with a relative permittivity (?_r) of 21.2, a quality factor (Q × f) of 52 360 GHz, and a temperature coefficient of resonant frequency (τ_f) of ?44.2 ppm/°C, when sintered at 1500 °C for 4 h. The τ_f value of the La₂MgGeO₆ ceramic doped with CaTiO₃ could be adjusted to zero. Particularly, 0.2La₂MgGeO₆-0.8CaTiO₃ ceramics have good microwave dielectric properties with τ_f = +2.1 ppm/°C, Q × f = 15 610 GHz, and ?_r = 40.3.     

Chirality‐Based Biosensors

The fabrication of chiral nanostructures gives rise to characteristic chiroptical activity, which can be used for chirality‐based biosensors. Great progress is made in the use of nanoassemblies for the construction of chiral nanoparticle dimers, pyramids, helices, and twisted structures, and their chiroptical activities correlate with diverse structural geometries and enantiomeric configurations. In DNA‐hybridization‐based chiral nanoassemblies, the assembly parameters, such as the components, gaps, multicomponents, and the aftergrowth of metal, can result in multiple bands and enhanced chiroptical effects. Based on known chiral nanostructures, the existing chiral nanoassembly‐based biosensors together with their targets and signal amplification strategies are reviewed. Chirality involves multiple signals, and multitarget biosensors are introduced with newly developed chiral architectures for the accurate and reliable monitoring of biomarkers in living cells. The interactions between chiral nanoarchitectures and biosystems are also highlighted, which are important not only in the chiral dynamic switching of nano‐objects for biomonitoring, but also in manipulating cell growth, proliferation, and adhesion. The future perspectives on chiral fabrication and its use in biosensors are also comprehensively discussed.     

WDM-PON技术在5G前传承载中的应用研究

前传在5G(第五代通信技术)承载网性能与网络优势发挥上起到越来越重要的支撑作用。文章通过各类技术在5G前传承载中的应用研究,充分对比差异及优缺点,得出C-RAN(集中化无线接入网)方式下高速WDM-PON(波分复用无源光网络)作为前传技术具备建网快捷、建设成本低、运营维护简便等多种优势,为WDM-PON技术在5G前传网络中的规模部署提供有力支撑,也能更快推动WDM-PON产业链的成熟和发展。     

以用户为中心的可见光通信协作传输中训练资源分配算法

以用户为中心的可见光通信协作传输是近年来出现的新架构,这导致虚拟小区之间出现重叠。为避免导频污染问题,每个虚拟小区中的光接入点(AP)或者虚拟小区中选择相同AP的用户发送的训练序列应该是正交的。针对可见光通信中以用户为中心的协作网络,研究训练资源的正交分配问题,提出了一种新的导频分配算法,联合导频分配和用户选择问题,以期最大限度地增加虚拟小区内可被接入的用户数。分析和仿真结果表明,该导频分配方案可以有效改善导频污染问题,提高训练资源利用率,并且相比已有的导频分配方案,性能有所改进。     

退火温度对冷轧DP980钢力学性能的影响

利用连续退火模拟机对DP980试验钢进行了连续退火试验,并通过扫描电镜、电子背散射衍射、透射电镜等研究了不同退火温度下(775、800、825和850 ℃),试验钢显微组织的演变规律和力学性能的变化趋势。结果表明:试验钢的屈服强度随着退火温度的升高而不断增大(从705 MPa增大到850 MPa),抗拉强度和断后伸长率则随着退火温度的升高而不断减小(抗拉强度从1150 MPa减小到1030 MPa;伸长率从8.9%减小到5.3%),这与试验钢的显微组织构成和形态分布密切相关。此外,不同退火温度下,试验钢的加工硬化率曲线均呈现单调下降的趋势。     

自适应SA-PSO优化的威布尔混合分布参数估计方法及应用

针对采用传统参数估计方法得到的模型拟合误差较大的问题，建立多重威布尔混合分布参数估计的非线性最小二乘模型，并提出基于模拟退火（SA）思想的自适应粒子群（PSO）算法进行求解。在PSO算法优化过程中，采用自适应方法调整惯性权重和加速因子，加快其收敛速度；引入模拟退火机制，根据Metropolis准则确定最优粒子的取舍，改善其全局搜索能力。将该方法应用到某型柴油机喷油器失效分布的参数估计中，并与图解法、基于Levenberg-Marquardt的非线性最小二乘法、标准PSO算法、自适应PSO算法求解的结果进行比较，分析所提方法的优化性能及精度。结果表明，该方法能够有效提高多重威布尔混合分布模型参数估计的精度和效率。     

大统矿业超高水充填开采制浆系统设计研究

煤炭作为我国的主要能源，在国民经济发展中具有不可取代的作用。矿井面临资源枯竭的困境时，尽可能多地采出煤炭是企业存续发展的当务之急。山东省兖州市大统矿业有限公司杨庄煤矿九采区3煤层1997—2005年进行了开采，由于受当时设备和技术的限制，仅回采一分层2.2 m。为挖掘企业潜力，充分利用煤炭资源，采用超高水充填法开采剩余分层和浅部煤炭资源。结合矿井实际情况提出适应矿井的高水充填系统布置方案，在地面建设制浆站，通过专门的设备将材料骨料制成浆液，然后运用管路将浆液输送至采空区进行充填。超高水材料制浆充填系统可服务于九采区全部充填工作面，每小时制浆生产能力为320 m³，每天生产1班8 h，约2 500 m³ 可以满足2个工作面的充填开采需要，极大提高了制浆充填效率，取得了良好的效果和经济社会效益。     

早冠丝瓜406新品种的选育

早冠丝瓜406是以S4为母本、X06为父本配制而成的一代杂种.极早熟,植株主蔓分枝性强,生长性强盛;雌花节位低,首朵雌花着生于主蔓第5节~7节,采收期为播种后58 d^60 d开始;嫩瓜呈长棒形,果端较圆,果皮深绿色,单果重0.5 kg^0.9 kg,果实纵径42 cm^50 cm,横径3.7 cm^4.2 cm,前期产量为16772.0 kg/hm^2,总产量可达47447.5 kg/hm^2.适合长江流域、云贵高原及湖南地区早春设施和露地栽培.