Electronic structure and peculiar bonding properties of NdNiMg5 from first principles

The newly found ternary compound NdNiMg₅ has been studied within DFT based methodologies. Results of cohesive energy, charge transfers, elastic constants and electron localized function mapping as well as electronic structure and bonding properties have been compared with those of isostructural binary NdNi. The calculation results have shown that Mg substructures interlayering NdNi – like slabs exhibit different magnitudes of charge transfers all within range of metallic behavior and the different Mg substructures selectively bind with Nd and Ni substructures. As a consequence an enhanced cohesion with respect to binary intermetallic NdNi is identified. The whole set of elastic constants and their combinations in orthorhombic symmetry confirm the mechanical stability of NdNiMg₅ with larger compressibility and less ductility (more brittleness) with respect substructures to NdNi. While in an intermetallic compound such as NdNi the bonding is ensured mainly by Nd–Ni interaction, in NdNiMg₅ Nd–Ni, Nd–Mg, Ni–Mg as well as Mg–Mg participate to the bonding and the extra electrons brought by Mg are found within bonding states thus illustrating furthermore the enhanced cohesion of the ternary versus the binary systems.     

Normal ordering problem and the extensions of the Stirling grammar

The purpose of this paper is to investigate the connection between context-free grammars and normal ordered problem, and then to explore various extensions of the Stirling grammar. We present grammatical characterizations of several well known combinatorial sequences, including the generalized Stirling numbers of the second kind related to the normal ordered problem and the r-Dowling polynomials. Also, possible avenues for future research are described.     

Antenna calibration technique based on channel prediction in time-varying TDD-MIMO system

The traditional antenna calibration for time division duplex multiple input multiple output (TDD-MIMO) systems assume that free-space channel keeps constant during calibration, which is unreasonable under the high-speed rail and other time-varying channel scenarios for time variability can cause calibration error. This paper analyzes the performance of traditional antenna calibration methods, and then proposes an antenna calibration method based on Wiener channel prediction for time-varying TDD-MIMO system. Through theoretical derivation, we get the capacity formula of the TDD-MIMO system using traditional antenna calibration and antenna calibration based on channel prediction. The theoretical analysis and simulation results both indicate that the performance degradation of antenna calibration can be caused by time-varying channel and the prediction algorithm proposed in the paper can well compensate for the performance loss and significantly improve the antenna calibration performance for time-varying TDD-MIMO system.     

The empty wagons adjustment algorithm of Chinese heavy-haul railway

The paper studied the problem of empty wagons adjustment of Chinese heavy-haul railway. Firstly, based on the existing study of the empty wagons adjustment of heavy-haul railway in the world, Chinese heavy-haul railway was analyzed, especially the mode of transportation organization and characteristics of empty wagons adjustment. Secondly, the optimization model was set up to solve the empty wagons adjustment of heavy-haul railway and the model took the minimum idling period as the function goal. Finally, through application and solution of one case, validity and practicability of model and algorithm had been proved. So, the model could offer decision support to transport enterprises on adjusting empty wagons.     

三维荧光光谱结合二阶校正方法同时测定水中两种酚类

水是生命之源,人们日常生产生活离不开水。近年来水体污染日趋严重,已经危害到人类的健康。酚类化合物(Phenolic Compound)是一种广泛存在且很难降解的有机污染物,指的是芳香烃中苯环上的氢原子被羟基取代所生成的含羟基衍生物,毒性很强,对动植物及人类的生命活动有严重危害。实验研究对象选取间苯二酚(resorcinol,RES)和对苯二酚(hydroquinone,HYD)来配制待测样本,并且在其中3组预测样本中加入苯酚(phenol,PHE)作为干扰物,待测样本和空白溶剂分别用FS920稳态荧光光谱仪(edinburgh instruments,EI)扫描得到荧光光谱数据。对所得到的数据通过扣除空白溶剂法来消除拉曼散射的影响,得到的数据在消除干扰的同时最大程度保留下来原光谱所包含的重要信息。校正后光谱变得更加圆滑,荧光强度显著增强,因此,校正处理后的光谱信息更为准确。利用三维荧光光谱(EEM)结合平行因子分析(PARAFAC)和交替惩罚三线性分解(APTLD)两种二阶校正方法,分别完成在不含干扰物和含有干扰物、同时激发-发射光谱严重重叠时对间苯二酚、对苯二酚的快速、直接、准确测量,并给出定性、定量分析结果。PARAFAC算法对混合体系的组分数(即化学秩)较敏感,组分数选取过大易使其陷入计算"沼泽",迭代次数增多,计算耗时变长。故本文利用核一致诊断法(CORCONDIA)预估计出准确的组分数,保证PARAFAC算法更加快速准确。从定性分析结果知,当不含有干扰物时,PARAFAC能够准确分辨出间苯二酚和对苯二酚,二者荧光峰位置极为接近,很难用传统方法分辨,体现出将三维荧光光谱技术与化学计量学二阶校正方法相结合所具有的"二阶优势";定量分析结果给出,在有干扰物共存时,分别应用两种二阶校正法解析光谱数据结果显示:PARAFAC的浓度预测回收率为93.4%±0.5%~97.1%±1.0%,预测均方根误差小于0.190 mg·L^-1;APTLD的浓度预测回收率为95.9%±1.6%~97.2%±0.8%,预测均方根误差小于0.116 mg·L^-1,通过比较两种方法性能得:PARAFAC对待测物组分数敏感,对待分解的光谱数据严格线性要求高;而APTLD对混合物组分数不敏感,计算速度快,抗噪声能力较强,结果稳定,具有较明显的优势。     

Quantitative measurement of hard X-ray spectra from laser-driven fast ignition plasma

Absolute Kα line spectroscopy is proposed for studying laser–plasma interactions taking place in the Au cone-guided fast ignition targets. X-ray spectra ranging from 20 to 100 keV were quantitatively measured with a Laue spectrometer composed of a cylindrically curved crystal and a filter-absorption method for Bremsstrahlung continuum emission. The absolute sensitivities of the Laue spectrometer systems were calibrated using pre-characterized laser-produced X-ray sources and radioisotopes. The integrated reflectivity for the crystal is in good agreement with predictions by an X-ray diffraction code. The energy transfer efficiency from incident laser beams to hot electrons, as the energy transfer mechanism, is derived from this work. The absolute yield of Au and Ta Kα lines were measured in the fast ignition experimental campaign performed at Institute of Laser Engineering, Osaka University. Applying the hot electron spectrum information from electron spectrometer and scaling laws, the energy transfer efficiency from the incident LFEX, a kJ-class PW laser, to hot electrons was derived for the first time.     

Chemical synthesis and characterization of manganese oxide coated Ni particles

Nanosized Ni particles with an average diameter of about 8 nm were prepared by reducing of NiCl 2 with sodium borohydride (NaBH 4 ) in aqueous solution. By moderate annealing in protective atmosphere, the composite grew up to be 15-20 nm particles. Both of the as-prepared and annealed Ni particles were coated by a layer of manganese oxide via decomposition reaction in aqueous KMnO4 solution. Hysteresis loops of as-prepared samples show a large increase in the magnetization with decreasing temperature and an unsaturated component at high magnetic field. In contrast, the ferromagnetic characteristics of annealed one are much stronger with large magnetization and coercivity. The thermomagnetic curves verified the coexistence of ferromagnetic Ni and antiferromangetic Mn oxide phases. But there exists no exchange bias behavior in the samples, even though the interface structure between the ferromagnetic Ni core and the antiferromagnetic manganese oxides has been distinctly formed. The absence of exchange bias probably originates from the weak ferromagnetic characteristic of Ni cores.     

Cladding-ring-equivalent effective index method for analyzing the propagation characteristics of multi-cladding photonic crystal fibers

Cladding-ring-equivalent effective index method (CREEIM) is proposed to analyze the propagation characteristics in the multi-cladding photonic crystal fibers (MCPCFs). The effective indices and dispersions of the step index two and three-cladding structures are calculated with the Sellmeier formula. The accuracy of CREEIM is competitive to the results calculated by the multipole method (MPM). With different structure parameters, the differences between two methods are evaluated with the relative error R_E of effective index and relative difference R_D of dispersion. This method is also used to analyze the mode cut-off and nonlinear characteristics in the three-cladding structure PCFs by calculating the mode effective index n_eff instead of complex mode field distribution.