回归系数的混合估计与最小二乘估计的一个新的相对效率

本文对具有附加信息的线性回归模型中的混合估计与最小二乘估计给出了一种新的相对效率,研究了新的相对效率与其它几种相对效率的关系,得出了新的相对效率的上、下界.     

逆奇异值问题的相对广义牛顿法

本文用另一方法证明了非对称矩阵的奇异值是处处强半光滑的,并利用这一性质给出求解逆奇异值问题的相对广义牛顿法,该方法具有Q-二阶收敛速度.     

Communication Roles, Perceived Effectiveness, and Satisfaction in an Environmental Management Program

Earlier research has shown a relationship between various forms of structural centrality and perceived leadership and role satisfaction in small experimental groups. The limited amount of research on this topic in naturally occurring social networks has yielded results that often conflict with one another. Different results have generally been attributed to possible differences in task environments. This paper examines the relationship between two types of structural centrality and perceived influence, role satisfaction, and perceived effectiveness in an environmental resource management program. Findings in this paper suggest that the observed differences in relationships between the network and other variables is partly a function of global network properties (e.g., marginality of subgroups) and related task environments. This revised version was published online in August 2006 with corrections to the Cover Date.     

TCDD的密度泛函理论研究

用B3LYP/6-311G~(**)方法全优经计算22个四氯二苯并对二（左口右恶）英（ 简称TCDD）分子，得到几何构型、总能量、标准熵、标准焓和标准自由能。将2， 3，7，8－TCDD的计算构型与X射线衍射实验测定值进行了比较。计算结果表明，总 能量、标准焓和标准自由能与氯原子量换位置的相关性很高（r > 0.997）.1,3,6, 8-TCDD的总能量处自由能最低，即最稳定，以此参照，得到异构体的总能量的相对 稳定性顺序和自由能的相对稳定性顺序。1,3,7,9－TCDD的稳定性次之，1,3,7,8- TCDD居第三，将这二个顺序与焚烧炉产生的TCDD异构体和合成的异构体对的生成面 分比进行了比较，说明焚烧炉中产生的TCDD和合成的TCDD对的分布主要受热力学控 制。     

~(19)F-NMR法测定聚醚多元醇中伯羟基的相对含量

<正> 聚醚多元醇是聚氨酯材料的主要原料之一.多元醇中伯羟基含量的多少对反应活性有着直接的影响,因此,准确地测定伯羟基含量已成为许多研究者关心的课题,并已报道了不少测定方法,其中主要包括化学动力学方法、~1H-核磁共振(NMR)法和~(19)F-NMR法,~1H-NMR法系利用不同的酰化剂,将聚醚多元醇酰化后测其酰化物的~1H-NMR谱,从伯、仲羟基相应的酯基氢的积分比例来计算伯羟基的相对含量,但由于体系中存在其它含氢基因,且是大量的,使测量困难或应用受到限制.~(19)F-NMR法测伯羟     

杂多阴离子[GeMo12O40]4-α/β异构体的密度泛函研究

采用密度泛函方法，在DND基组水平上，对[GeMo12O40]^4-杂多阴离子最常见的α和β异构体进行了几何构型优化，得到了与X射线晶体衍射实验结果相一致的结构参数，并在此基础上进行了振动频率分析，得到了杂多阴离子的电子结构、热力学特性和振动光谱，通过定义α，β异构体异构化反应的Gibbs函变△Gα-β与温度的关系，研究了这两种异构体的相对稳定性．结果表明：低温时α异构体更稳定，高温时β异构体更稳定些，550K左右为转变点．振动频率分析得到2种异构体的最强峰位于4个频率位置，分别指认为vax(Mo-Od)，vas(Mo-Od)，vas(Mo-Oc-Mo)，vas(Ge-Oa)，vas(Mo-Ob-Mo)振动，与红外光谱(IR)的特征振动峰相对应，观察到了特征频率的振动模式，从理论计算角度说明了Rocchiccioli—Deltcheff关于振动模式的设想是合理的．     

Thermodynamic properties of aqueous organic mixtures near the critical demixing: Cases of 2,6-dimethylpyridine and of 2-isobutoxyethanol

Phase diagrams, volumes and heat capacities of aqueous mixtures of 2,6-dimethylpyridine (2,6-L) and 2-isobutoxyethanol (iBE) and activities of 2,6-L in aqueous mixtures were measured in the monophasic region near the lower critical solution temperature (LCST). With 2,6-L some measurement were also made just above the LCST. From the temperature dependence of these data, partial molar relative enthalpies (2,6-L), expansibilities and the temperature derivative of heat capacities were calculated and show that iBE undergoes a microphase transition at low concentration which is not related to the phase separation. On the other hand, the properties of 2,6-L in the water-rich region at temperatures well below the LCST indicates that this solute has only a slight tendency to associate. The heat capacities of 2,6-L show an important increase near the LCST. Such changes are not observed for iBE and other alkoxyethanols and amines since these systems already exist in the form of microphases; the partial molar properties of iBE near the LCST are nearly equal to the molar values of the pure liquid, and the changes in thermodynamic properties corresponding to the macroscopic phase transition, are therefore too small to be measured by the present techniques.     

Investigation of homo- and heterodimer alkali metal cation complexes of resorc[4]arenes by electrospray ionization mass spectrometry

Resorc[4]arenes are compounds with interesting properties, mainly because of their ability to form host-guest complexes with the guest located inside the cavity. The size of the guest limits the complexation, as shown by a competition experiment with tetraalkylammonium ions of different size. By electroscopy ionization tandem mass spectrometric experiments on resorc[4]arene heterodimers bearing an alkali metal ion as guest, it was found that there must be two different binding mechanisms for alkali metal ions with high surface charge density (Li(+) and Na(+)) on the one hand compared with those with a lower surface charge density on the other hand (K(+), Rb(+), Cs(+)).     

纳米镍-铁合金/膨胀石墨复合材料的制备、表征及其电磁屏蔽性能

The composites with nano-particles of Ni-Fe alloys dispersed on the nano-layers of expanded graphite (EG) were prepared by the impregnation of EG with ethanol solutions of nickel and iron acetates， followed by drying and reduction in H₂. The square nano-particles of Ni-Fe alloys with particle sizes of mainly 20～40 nm were found to be well spread on the layers of EG. The alloy nano-particles exhibited high shielding effectiveness (SE) for electromagnetic radiations at low frequencies due to their high magnetic conductivity. Since EG is electronically conductive and displayed high SE at high frequencies， the composites exhibited good SE at wide range of frequencies. The electric and magnetic conductivities of the composites could be monitored through regulating the loadings of alloy nano-particles on EG， and it was found that the composites with 20%～40% of the alloys exhibited good SE. Specifically， the composite 27%Ni-3%Fe-EG showed the excellent SE from 66 to 110 dB at the frequencies from 300 kHz to 1.5 GHz.     

Synthesis and thermal stability of silicon-containing esters of phosphorus acids

A number of trialkylsilylmethyl diphenyl phosphates MeRR′SiCH₂OP(O)(OPh)₂ (1a-e: R=Et (a), Pr (b), CF₃CH₂CH₂ (c, e), Me₃SiCH₂ (d); R′=Me (a-d), Et (e)) were synthesized and their thermal rearrangement, of the 1,2-shift type, was studied. The rearrangement consists of the migration of an alkyl group from Si atom to the methylene carbon atom and gives the corresponding silyl esters. The rate of the rearrangement was found to increase in the order1d<1b<1a<1 (R=R′=Me)<1c corresponding to the enhancement of the total inductive effect (−I) of the substituents at the Si atom. The relative migration ability of the substituents at the Si atom, determined by GC/MS analysis of the disiloxane fraction resulting from hydrolysis of pyrolyzed phosphates1a-e, increases in the order R=Pr<Et<CF₃CH₂CH₂<Me≪Me₃SiCH₂, which differs substantially from the order in which the rate of the rearrangement of phosphates1a-d changes. The electronegativity of the migrating group affects noticeably the relative ability to migrate. For Part 4, see Ref. 1. Deceased. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 1767–1772, September, 1998.