铅测定中的二条谱线对比

本文介绍了对铅的二条灵敏谱线进行的实验对比,结果证明２１７．０ｎｍ谱线的灵敏度增加一倍以上,其他指标也接近２８３．３ｎｍ谱线,可以用于卫生检测。     

A Hidden Chaotic System with Multiple Attractors

This paper reports a hidden chaotic system without equilibrium point. The proposed system is studied by the software of MATLAB R2018 through several numerical methods, including Largest Lyapunov exponent, bifurcation diagram, phase diagram, Poincaré map, time-domain waveform, attractive basin and Spectral Entropy. Seven types of attractors are found through altering the system parameters and some interesting characteristics such as coexistence attractors, controllability of chaotic attractor, hyperchaotic behavior and transition behavior are observed. Particularly, the Spectral Entropy algorithm is used to analyze the system and based on the normalized values of Spectral Entropy, the state of the studied system can be identified. Furthermore, the system has been implemented physically to verify the realizability.     

Relativistic effects and the halogen dependencies in the 13C chemical shifts of CH4−nIn,CH4−nBrn,CCl4−nIn,and CBr4−nIn (n=0–4)

Linear and nonlinear halogen dependencies of the ¹³C magnetic shielding constants of CH_4−nI_n, CH_4−nBr_n, CCl_4−nI_n, and CBr_4−nI_n were fairly reproduced by the ab initio generalized unrestricted Hartree–Fock (GUHF)/finite perturbation (FP) method including spin‐orbit (SO) interaction and spin‐free relativistic (SFR) terms. As seen from the experimental trends, the calculated ¹³C chemical shifts in CCl_4−nI_n and CBr_4−nI_n depend linearly on n=0–4, while those in CH_4−nI_n and CH_4−nBr_n depend nonlinearly. We found that both the linear and nonlinear dependencies are due to the relativistic effects, and especially due to the Fermi–Contact (FC) term originating from the SO interaction. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 528–536, 2001     

Equivalence classes of central semiregular relative difference sets

A semiregular relative difference set (RDS) in a finite group E which avoids a central subgroup C is equivalent to a cocycle which satisfies an additional condition, called orthogonality. However the basic equivalence relation, cohomology, on cocycles, does not preserve orthogonality, leading to the perception that orthogonality is essentially a combinatorial property. We show this perception is false by discovering a natural atomic structure within cohomology classes, which discriminates between orthogonal and non‐orthogonal cocycles. This atomic structure is determined by an action we term the shift action of the group G = E/C on cocycles, which defines a stronger equivalence relation on cocycles than cohomology. We prove that for each triple (C, E, G), the set of equivalence classes of semiregular RDS in E relative to C is in one to one correspondence with the set of shift‐orbits of the (Aut(C) × Aut(G))‐orbits of orthogonal cocycles. This determines a new algorithm for detecting and classifying central semiregular RDS. We demonstrate it, and propose a 7‐parameter classification scheme for equivalence classes of central semiregular relative difference sets. © 2000 John Wiley & Sons, Inc. J Combin Designs 8: 330–346, 2000     

NMR Properties of Polylithiated C60

Endohedral, ¹³C, ⁷Li, and nucleus‐independent (NICS) chemical shifts are reported for selected Li_nC₆₀ isomers (n = 6, 12, 18) at the GIAO (gauge‐including atomic orbitals)‐SCF/DZP//BP86/3–21G level. Li₆C₆₀ closely resembles C₆₀^6– in terms of NMR criteria for aromaticity, as evidenced by an exceptionally high endohedral shielding. In contrast, nonaromaticity is indicated for Li₁₂C₆₀, based on a positive endohedral chemical shift. NICS and δ(endo) values very similar to those of Li₁₂C₆₀ are obtained for Li₁₈C₆₀. According to population analysis, indeed the same number of electrons are transferred to the fullerene cage in both cases. Endohedral chemical shifts, accessible via ³He NMR of the corresponding endohedral helium compounds, could thus be a valuable indicator for the extent of reduction of the C₆₀ molecule. Energetic estimates suggest that in the bulk, Li₁₂C₆₀ should be unstable with respect to decomposition into Li₆C₆₀ and lithium metal.     

基于高光谱技术的有机鸡蛋与普通鸡蛋鉴别

当今全球范围内有机食品行业发展迅速,体现出消费者对食品质量安全的重视.相比于普通鸡蛋,有机鸡蛋因严格的生产条件以及更高的营养价值生产成本更高、售价更贵.市面上所销售的有机鸡蛋虽取得了严格有机食品认证标识,但依旧不能阻止不法份子将普通鸡蛋冒充有机鸡蛋销售,从而谋取利润.这一行为不仅会损害有机鸡蛋生产商的利益,也降低了人们...     

文物红色系颜料高光谱识别指数研究

红色系矿物颜料曾被艺术家们大量地使用在古画和古建筑上.正确地识别出不同种类的红色系颜料对于文物监测与修复具有重要意义.传统的颜料识别主要依靠化学分析,不仅识别速度慢、识别范围小,而且对文物进行取样操作会造成文物的永久损伤.高光谱技术对颜料进行无损识别可以很好地解决这些问题.选用辰砂、胭脂、银朱、朱膘、朱砂、赭石、赭粉、...     

钡铁氧体前驱体高能球磨过程的红外拟合光谱分析

高能球磨法是材料制备过程中常用的方法,通过物料在高速运转的过程中进行磨合而产生晶体空位缺陷,实现元素的掺杂,进而发生化学吸附或化学反应,合成产生新的物相,对于后续合成材料的性能有很大影响.钡铁氧体具有良好的磁性能,被用于功能材料制备的诸多领域.采用高能球磨法制备钡铁氧体前驱体,利用XRD,SEM和FTIR检测方法考察不...