Novel processing of Barkhausen noise signal for assessment of residual stress in surface ground components exhibiting poor magnetic response

The Barkhausen Noise Analysis (BNA) technique has been utilised to assess surface integrity of steels. But the BNA technique is not very successful in evaluating surface integrity of ground steels that exhibit poor micro-magnetic response. A new approach has been proposed for the processing of BN signal and two newly proposed parameters, namely ‘count’ and ‘event’, have been shown to correlate linearly with the residual stress upon grinding, with judicious choice of user defined ‘threshold’, even when the micro-magnetic response of the work material is poor. In the present study, residual stress induced upon conventional plunge surface grinding of hardened bearing steel has been investigated along with unhardened bearing steel for benchmarking. Moreover, similar correlation has been established, when primarily compressive stress is induced upon high speed grinding using cBN wheel with moderately deep cut suppressing the micro-magnetic response from the ground medium carbon steel as the work material.     

YnN(n=2-12)团簇的结构与性质研究

在密度泛函理论框架下,用广义梯度近似（GGA）的方法研究YnN（n=2-12）团簇的电子结构,系统计算了它们的基态束缚能Be（eV）、最高占据轨道（HOMO）与最低未占据轨道（LUMO）之间的能隙、二阶能量差分 (au)、离解能 (au)、团簇的总磁矩Mt（ ）,最近邻N原子的Y原子所带的局域电荷QY（C）和磁矩MY（ ）、掺杂原子N所带的局域电荷QN（C）和磁矩MN（ ）。研究表明,Y6N、Y8N、Y10N的基态具有较高稳定性;对于YnN（n=2-12）的所有团簇,电荷总是由Y原子转移到N原子,YnN（n=2-12）团簇中Y—N表现为离子键的性质;当n=3,4,5,9,10,11,12时,团簇的磁矩为零,团簇的磁性消失,当n=2,6,7,8时,团簇具有磁性,其中n=6时,团簇的磁性最强。     

Hg2CuTi型Mn2NiGe合金的电子结构、磁性对压力、四方变形的响应

运用基于密度泛函理论的第一性原理方法,研究了Hg2CuTi型 Mn2NiGe合金的电子结构对外加压力的响应以及Mn2NiGe的电子结构、磁性对四方变形的响应．结果表明：i）随着外加压力的增加,因Ni、Mn原子间距的减小而导致杂化程度的增强,使得态密度整体向低能区域移动,同时,态密度幅度整体略有减小;ii）在由奥氏体相到马氏体相的变形中,同样因Ni、Mn原子间距的减小而导致杂化程度的增强,占据态的态密度向低能区域移动,体系的能量降低,同时,成键态向低能方向移动,反键态向高能方向移动,能带变宽,成键作用加强,最终导致在马氏体相中的稳定性增大;iii）在四方变形过程中,Mn2NiGe总磁矩的变化主要由Ni原子磁矩的变化所产生．     

磁二向色性光电发射

磁二向色性光电发射（ Ｍ Ｄ Ｐ Ｅ） 技术是结合光电子能谱和磁二向色性技术的磁学测量方法,近年来已成为研究表面、界面和薄膜等低维体系磁性的重要手段。本文概述了其基本原理和实验方法,着重探讨几种 Ｍ Ｄ Ｐ Ｅ 效应的产生及其理论解释,并介绍了 Ｍ Ｄ Ｐ Ｅ 在磁性过渡金属、稀土金属低维体系中的应用。     

Synthesis,Crystal Structure,and Physical Properties of the New Chain Alkalioxocuprate K3Cu2O4

Single crystals of K₃Cu₂O₄ were prepared by the azide/nitrate route from respective stoichiometric mixtures of KN₃, KNO₃ and CuO, at 923 K, whereas powder samples were synthesised by solid state reaction of K₂O, KCuO₂ and CuO, sealed in gold ampoules and treated at 723 K. According to the single crystal structure analysis (Cmcm, Z = 4, a = 6.1234(1), b = 8.9826(2), c = 10.8620(2) Å, R₁ = 0.044, R₂ = 0.107), the main structural feature are undulating CuO₂ chains built up from planar, edge sharing CuO₄ square units. From an analysis of the Cu–O bond lengths, the valence state of either +2 or +3 can be unambiguously assigned to each copper atom. The magnetic susceptibilities show the dominance of antiferromagnetic (AFM) interactions. At high temperatures, the magnetic behaviour can be fitted with the Curie–Weiss law (μ_eff = 1.84μ_B, Θ = –105 K). The experimental data can be very well described by a uniform Heisenberg chain with a nearest‐neighbour spin intrachain interaction (J_nn) of ~ 101 K.     

二维铜配合物{[Cu2(BIPA)2(bpe)2]·H2O}n的合成、晶体结构及磁性

本文以5-溴间苯二甲酸(H2BIPA)、1,2-双(4-吡啶基)乙烷(bpe)和Cu(NO3)2.3H2O水热反应得到了一个配位聚合物{[Cu2(BIPA)2(bpe)2].H2O}n,并用元素分析、红外光谱以及X-射线单晶洐射对其进行了表征。该晶体属三斜晶系,P1空间群。Cu(Ⅱ)离子通过2个BIPA配体桥联形成一维梯状链,再通过bpe配体连接成二维层状结构。变温磁化率显示羧酸桥联的双核铜之间存在弱的反铁磁相互作用。     

固相萃取气相色谱-质谱法测定葡萄酒中118种农药残留量

样品(10g)先后用20mL及15mL乙腈超声波提取118种农药残留,经盐析并离心除水液液分配,所得提取液经40℃旋转蒸干,残渣溶于乙腈甲苯(3+1)混合溶液5mL中,溶液经Carb/PSA双层固相萃取小柱净化,淋出液蒸至近干并溶于丙酮-正己烷(1+1)混合溶液1.0mL中,供气相色谱质谱分析。分析中采用HP-5MS毛细管色谱柱及EI离子源和选择离子扫描方式,外标法定量。方法的测定下限(10S/N)在0.01～0.031mg·kg~(-1)之间,在加标水平为0.05mg·kg~(-1)时,方法回收率为67%～124%,相对标准偏差(n=5)小于12.2%。     

New Cu(II)4 and Zn(II)4 complexes: Synthesis, characterization and magnetic and biological studies

Two new isomorphous tetranuclear complexes [Cu₄L₂(4,4′-bipy)₂]·(ClO₄)₄·2CH₃CN·2H₂O (1) and [Zn₄L₂(4,4′-bipy)₂]·(ClO₄)₃·CH₃O·4H₂O (2) have been obtained and fully characterized (where bipy = bipyridine, H₂L = macrocycle is the [2+2] condensation product of 2,6-diformyl-4-fluoro-phenol and 1,4-diaminobutane). They exhibit wheel-like configuration in which two 4,4′-bipy molecules connect two dinuclear [M₂L]²⁺ units. The interactions of the complexes with calf thymus DNA were studied by UV-Vis and CD spectroscopic techniques. The binding constants of 1 and 2 are 2.27 × 10⁶ and 3.89 × 10⁵ M⁻¹, respectively. The magnetic measurement of 1 reveals that there are strong antiferromagnetic coupling (J = -272.6 cm⁻¹) between two Cu(II) ions in the macrocyclic unit and ferromagnetic interaction (j′ = 41.7) between the Cu(II) ions in two adjacent macrocyclic units. Furthermore, the cyclic voltammogram of 1 shows that it undergoes two quasi-reversible processes with the half wave potentials -0.232 and -0.606 V, respectively.     

Evaluation of oxygen pressurized microwave-assisted digestion of botanical materials using diluted nitric acid

The feasibility of diluted nitric acid solutions for microwave-assisted decomposition of botanical samples in closed vessels was evaluated. Oxygen pressurized atmosphere was used to improve the digestion efficiency and Al, Ca, K, Fe, Mg and Na were determined in digests by inductively coupled plasma optical emission spectrometry (ICP OES). Efficiency of digestion was evaluated taking into account the residual carbon content (RCC) and residual acidity in digests. Samples were digested using nitric acid solutions (2, 3, 7, and 14 mol L⁻¹ HNO₃) and the effect of gas phase composition inside the reaction vessels by purging the vessel with Ar (inert atmosphere, 1 bar), air (20% of oxygen, 1 bar) and pure O₂ (100% of oxygen, 1 bar) was evaluated. The influence of oxygen pressure was studied using pressures of 5, 10, 15 and 20 bar. It was demonstrated that a diluted nitric acid solution as low as 3 mol L⁻¹ was suitable for an efficient digestion of sample masses up to 500 mg of botanical samples using 5 bar of oxygen pressure. The residual acidities in final digests were lower than 45% in relation to the initial amount of acid used for digestion (equivalent to 1.3 mol L⁻¹ HNO₃). The accuracy of the proposed procedure was evaluated using certified reference materials of olive leaves, apple leaves, peach leaves and pine needles. Using the optimized conditions for sample digestion, the results obtained were in agreement with certified values. The limit of quantification was improved up to a factor of 14.5 times for the analytes evaluated. In addition, the proposed procedure was in agreement with the recommendations of the green chemistry once it was possible to obtain relatively high digestion efficiency (RCC < 5%) using only diluted HNO₃, which is important to minimize the generation of laboratory residues.     

FTIR光谱高温气体浓度反演方法及残差结构分析

从理论和实验两方面分析了光谱线线宽随温度的变化规律.将HITRAN数据库中常温下的线强参数修正到了测量温度,进而得到合成校准光谱.将合成校准光谱和实验测得的光谱进行非线性最小二乘拟合,得到了不同温度下标准气体CO浓度.这种反演算法的浓度误差在常温下不超过5%,具有很高的精度,但随温度升高浓度误差逐渐增大.从残差光谱曲线...