The Chemistry of DPPH· Free Radical and Congeners

Since the discovery in 1922 of 2,2-diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl stable free radical (DPPH^·), the chemistry of such open-shell compounds has developed continuously, allowing for both theoretical and practical advances in the free radical chemistry area. This review presents the important, general and modern aspects of the chemistry of hydrazyl free radicals and the science behind it.     

家用变频空调室外机控制器PFC电路设计

PFC电路是家用变频空调室外机控制器基本的单元电路之一,根据控制电路的不同,分为无源和有源PFC两大类,有源PFC电路因其优点多而得到很好的发展。目前,有源PFC的整流滤波电路通常用少量大容值的铝电解电容组成,存在成本高和寿命短的问题。本论文介绍一种新的有源PFC高压整流滤波电路,它由多数量小容值铝电解电容并联组成,辅以电流均流化设计,有效降低电容的ESR值,减小电容的发热,提升控制器寿命。     

南阳盆地北缘更新世以来的构造演化特征

南阳盆地是白垩纪晚期以来持续发育的断陷盆地，通过对南阳盆地钻孔及河流阶地的研究，并结合ESR测年方法，对南阳盆地北缘更新世以来的构造演化特征进行了分析。结果表明：研究区冲洪积层主要由全新统、上更新统、中更新统组成，分别构成了湍河的Ⅰ级、Ⅱ级、Ⅲ级阶地；中更新统以来，研究区垂直升降运动较为明显，湍河下蚀作用十分强烈，多级阶地的结构体现了更新世中晚期以来的总体持续下蚀过程，且时间和空间上表现出不均衡性，其下蚀速率由慢至快又逐渐减缓。     

Supramolecular Assembly on Coordination of Azopolymer Complexes: A Review

This review gives an account of the coordination chemistry of supramolecular azopolymer complexes. The syntheses and structures of azomonomers and their azopolymer complexes were described. Spectral techniques such as (IR, ¹H-NMR, ESR) and thermal analysis were investigated. Supramolecular architectures assembled were exhibited through weak interaction including hydrogen bonding and π–π stacking. The spectral data indicate geometry of azopolymer complexes and the orbital reduction factors. ESR spectral data provided information about their structures on the basis of Hamiltonian parameters and degree of covalency. All the azopolymer complexes are ESR active due to the presence of an unpaired electron. The force constant F_U–O(mdyn/Å) and the bond length R_U–O (Å) of the U–O bond were calculated from the IR data and related to the electronic properties of the substituents. Wilson's method, the matrix method, Badger's formula, and the Jones and El-Sonbati equations were used to calculate the U–O bond distances from the values of the stretching and interaction force constants. The most probable correlations between U–O force constant to U–O bond distance were satisfactorily discussed in terms of Badger's rule, and the Jones and El-Sonbati equations. The thermal stability was investigated using thermogravimetric analysis. The results showed that the azopolymer complexes are mostly more stable than the homopolymer. The stability of the proton ligand/metal ligand constants in the monomeric and polymeric forms was studied carefully using potentiometery. Based on the thermodynamic functions, the dissociation process is nonspontaneous, endothermic and entropically unfavorable. The metal complexes that were formed exhibited spontaneous, endothermic and entropically favorable behavior.     

影响窗玻璃γ辐射响应的电子自旋共振波谱研究

为更好应用于人员剂量估算和事故等级测定,探索了影响窗玻璃电子自旋共振波谱剂量学性质的因素。实验将窗玻璃处理成不同粒度大小,分别研究研磨处理对本底信号和辐射信号的影响。给予窗玻璃样本不同照射剂量,存储在不同条件下,观察温度、光线、时间等对电子自旋共振波谱(ESR)信号的影响。对比了来源不同的窗玻璃剂量响应曲线和最小检测剂量。结果表明,前期样本处理对窗玻璃辐射信号并无明显影响,但会产生机械信号;温度越高,窗玻璃辐射信号越不稳定。高温加热(≥200 ℃,≥5 min)可使照射后的ESR信号衰退至本底信号;透明袋-灯光和黑袋存储条件下的样本结果大致相同:11小时信号强度衰减9%左右,150小时衰减约18%。透明袋-阳光样品:11小时信号衰减了17%,150小时衰减38%。三种存储条件下的样本在150小时左右之后均达到稳定状态;窗玻璃样品在g=2.005 7处ESR信号与吸收剂量线性相关,线性相关性系数因来源于不同生产厂家而有差异。窗玻璃最小检测剂量是4~5 Gy。因此,在窗玻璃作为剂量计的实践中,注意以上问题,建立合理的剂量评估操作程序,可以估算出更为准确的结果。     

Relative anisotropy of structures and ultrasound attenuation response between laboratory casting in permanent mould (vacuum induction melted) and casting processed through electroslag refining

Abstract

In the present study, ingots of 'modified 15CDV6' (0·3C–CrMoV) steel were laboratory melted and cast by the vacuum induction melting–electroslag refining (VIM–ESR) and VIM (water cooled steel mould) routes. The ingots have been evaluated for their relative anisotropy differences by ultrasound attenuation (UA) studies along respective radial and axial directions. The expected sources of UA are crystallographic texture and the presence of defects. These defects include inclusions, grain boundaries, segregation and microporosity. Apart from microporosity, the presence of defects has been characterised along the respective casting directions. Although both castings/ingots had gone through successive phase transformations after solidification (liquid→δferrite→austenite→ferrite), the electroslag refined (ESR) material had significantly more anisotropy in crystallographic texture, but insignificant anisotropy in inclusion distribution, as compared with the vacuum induction melted (VIM) material. The grain boundary character distributions and long range compositional fluctuations were similar and nearly isotropic between the two ingots. The ESR material, in general, was denser, which may indicate a lower presence of microporosity. Taking grain size differences into account, the UA estimated anisotropy was more for ESR material, a response clearly dominated by the anisotropy of the crystallographic texture. At a higher frequency, and correspondingly finer resolution for defects, the anisotropy owing to defects played a more dominant role, but even then the highest frequency of 2 MHz was not adequate to highlight a dominance of defect anisotropy.     

聚合物阴极钽电解电容器被膜技术研究

研究了以导电聚合物PEDOT作为阴极材料的高频低ESR有机片式固体钽电解电容器的被膜技术,重点讨论不同的聚合温度、掺杂浓度和驱溶温度对降低片式固体钽电解电容器ESR的影响.研究结果表明当聚合温度为0～10℃、掺杂浓度为3%(W),驱溶温度80℃时,将得到致密的主链掺杂有效的PE-DOT膜层,从而得到较低的ESR,并表现...     

板坯电渣重熔炉结晶器报废原因分析及改进措施

着重对舞钢公司40 t板坯电渣重熔炉结晶器的报废原因进行了分析研究,阐述了针对该类型结晶器所制定的维护、修复与报废标准,同时提出了延长结晶器使用寿命和降低结晶器使用成本方面的一些措施和设想展望。     

双极串联电渣重熔降低电耗的途径

从理论分析的方法找出双极串联电渣重熔工艺影响电耗的因素,再探究工业实践中生产板坯电渣锭用双极串联电渣炉降低电耗的途径,包括调整熔炼熔速、渣系配比及部分工艺参数等。