网络上两类物资联合最大流问题的极流特征

当网络上(诸如交通网络、通讯网络)有多种不同物资或信息同时分别从相应的发点输送到相应的收点,要求每条线路上各类物资或信息的输送量总和不超过线路的容量时,寻求所有物资的最大输送量的问题,就是所谓网络多种物资的最大流问题,这个问题在生产实际和理论上都有着重要的意义,1963年T.C.Hu提出了求两类物资联合最大流的标号方法,但是为了保证有限步达到最大流,要求边的容量是偶数。 本文是文献[3]的继续,用图论的语言描述了两类物资最大流问题极流的特征,并对标号方法作了一点修改,使得有限步得到最大流,或者在某一步得到极流后,保证以后的迭代是从极流到极流.这样因极流的个数是有限的,并且最大流总可以在极流上达到,从而保证了有限步内得到所要求的最大流,无须对边的容量作任何限制, 本文所提的算法是使图形特征很强的标号算法和线性规划的极点迭代结合起来,这就使得有可能把这种方法,推广到更大的一类问题中,例如,研究容量的改变对最大流量的影响。     

Studies of the pyrazine-bridged antiferromagnets Fe(pyz)mX2 (m=1, X=CF3SO3 −, NCO−; m=2, X=NCS−)

Mössbauer and magnetic susceptibility data are reported for the title complexes. The data demonstrate that these pyrazine-bridged complexes represent examples of low-dimensional lattices with anisotropic magnetic exchange arising from different interaction strengths of the bridging ligands.     

分子束研究GaAs和InP与氯的激光化学反应动态学

本文采用CW超声分子束和时间分辨质谱技术,研究了在紫外和可见(355nm和560nm)脉冲激光辐照下GaAs(100)和InP(100)表面与氯的激光化学反应动态学。由质谱和飞行时间谱测得反应的主要产物为GaCl_x和InCl_x(x=1,2),研究了激光波长和能量密度对产物飞行时间谱的影响,首次发现提高入射Cl₂分子的平动能对上述激光诱导气-固相反应有明显的增强作用。     

Controlling the torsion angle via adventitious cation binding

We report herein the synthesis of a linear binuclear ruthenium(II) complex, and the corresponding free ligand, for which the organic connector is a geometrically-constrained crown ether that binds added cations.     

Synthesis of a biphenyl-based cyclophane via benzidine rearrangement of a constrained m-nitrophenol derivative

The benzidine rearrangement of a constrained m-nitrophenol derivative results in production of a cyclophane comprising a biphenyl group and a polyether tether connected at the 4,4′ positions.     

Interpretation of isomer shift-quadrupole splitting correlations for pentacoordinate trimethyltin complexes

Linear correlations between ¹¹⁹Sn isomer shifts δ and quadrupole coupling constants e²qQ are noted for several series of pentacoordinate trimethyltin derivatives. The sign of the gradient of a δ versus e²qQ plot is interpreted as indicating whether the predominant effect on δ in a given series arises from rehybridization of the tin bonding orbitals or from a p-electron deshielding mechanism. Differences in magnitudes of the slopes are related to differences in the fractional s-character of the bonds between tin and the axial substituents.     

18O effects on the infrared spectrum and skeletal tunneling of tropolone

Infrared-absorption profiles observed for vibrational transitions of gaseous tropolone often show sharp Q branch peaks, some of them ultranarrow spikes, indicative of the band origins for vibrational state-specific spectral tunneling doublets. In this work oxygen isotope effects for two CH wagging fundamentals, the COH torsion fundamental, and the skeletal contortion fundamental are reported. They allow considerations to be given: (1) oxygen isotope effects on the vibrational frequencies and state-specific tunneling splittings; (2) the asymmetry offset of the potential-energy minima for 16O and 18O tropolone; and (3) additional details concerning previously proposed high J rotation-contortion resonances in the contortional fundamental. The new results help to characterize the skeletal contortion fundamental and support the joint participation of skeletal tunneling with H tunneling in the vibrational state-specific tautomerization processes of tropolone in its ground electronic state.     

The preparation and properties of perfluoro-N-heptylbromine(N) tetrafluoride

Reactions of $\text{n}$C₇F₁₅Br with elemental fluorine at 0°C have produced perfluoro-$\text{n}$-heptylbromine(V) tetrafluoride ($\text{n}$-C₇F₁₅BrF₄). This derivative of BrF₅ was characterized by IR, ¹⁹FNMR, mass spectroscopy and elemental analysis. The reactions of $\text{n}$C₇F₁₅BrF₄ with 1,2-dichlorohexafluorocyclopentene-1 (C₅F₆Cl₂) and 1,2-dichlorooctafluorocyclohexene-1 (C₆F₈Cl₂) were used to demonstrate in the fluorinating ability of $\text{n}$C₇F₁₅BrF₄.     

A Study of Synthesis, Immobilization and Catalytic Capability of Metalloporphyrin

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Determination of dimetridazole, ronidazole and their common metabolite in poultry muscle and eggs by high performance liquid chromatography with UV detection and confirmatory analysis by atmospheric pressure chemical ionisation mass spectrometry.

A method was developed for the determination of the nitroimidazole compounds dimetridazole (DMZ) and ronidazole (RNZ) and their common metabolite, 2-hydroxymethyl-1-methyl-5-nitroimidazole (2-OH-M). Extracts obtained from a clean-up process using strong cation exchange (SCX) solid phase extraction (SPE) can be analysed either by high performance liquid chromatography with UV detection (HPLC-UV) or by high performance liquid chromatography with atmospheric pressure chemical ionisation mass spectrometry (HPLC-APCI-MS) as a confirmatory method. Up to 20 samples can be extracted in approximately 4 h. The HPLC-UV analysis had a limit of detection of 0.5 microgram kg-1. Validation in chicken muscle fortified at a concentration of 5 micrograms kg-1 gave recoveries of 75% DMZ, 77% RNZ and 81% 2-OH-M with RSDs of 16.4, 11.3 and 14.0%, respectively (n = 17). Validation in egg fortified at the same concentration gave recoveries of 77% DMZ, 80% RNZ and 80% 2-OH-M, with RSDs of 14.9, 22.0 and 18.2%, respectively (n = 18). The limit of detection of the HPLC-APCI-MS method was 0.1 microgram kg-1 for DMZ and RNZ and 0.5 microgram kg-1 for 2-OH-M. This method gave mean recoveries in fortified egg samples of 65% DMZ, 87% RNZ and 75% 2-OH-M with RSDs of 22, 11 and 14%, respectively (n = 10). The ratios of the peak areas of the molecular ion and a fragment ion were monitored as added confirmation of the presence of the analyte. Both the HPLC-UV screening procedure and the HPLC-APCI-MS confirmatory method have subsequently been used for the analysis of several hundred samples as part of UK surveillance programmes.