On disjoint configurations in infinite graphs

For a graph A and a positive integer n, let nA denote the union of n disjoint copies of A; similarly, the union of ?₀ disjoint copies of A is referred to as ?₀A. It is shown that there exist (connected) graphs A and G such that nA is a minor of G for all n??, but ?₀A is not a minor of G. This supplements previous examples showing that analogous statements are true if, instead of minors, isomorphic embeddings or topological minors are considered. The construction of A and G is based on the fact that there exist (infinite) graphs G₁, G₂,… such that G_i is not a minor of G_j for all i ≠ j. In contrast to previous examples concerning isomorphic embeddings and topological minors, the graphs A and G presented here are not locally finite. The following conjecture is suggested: for each locally finite connected graph A and each graph G, if nA is a minor of G for all n ? ?, then ?₀A is a minor of G, too. If true, this would be a far‐reaching generalization of a classical result of R. Halin on families of disjoint one‐way infinite paths in graphs. © 2002 Wiley Periodicals, Inc. J Graph Theory 39: 222–229, 2002; DOI 10.1002/jgt.10016     

袋装砂井施工工艺及质量控制

介绍了广肇高速公路1-B标段软基处理中的袋装砂井施工工艺与工程质量控制,并列出了部份监测结果.     

Rigidity of Branch Groups Acting on Rooted Trees

Automorphisms of groups acting faithfully on rooted trees are studied. We find conditions under which every automorphism of such a group is induced by a conjugation from the full automorphism group of the rooted tree. These results are applied to known examples such as Grigorchuk groups, Gupta–Sidki group, etc.     

A Criterion for Spectrum Decomposition

We obtain a necessary and sufficient condition for the decomposition of the spectrum of an arbitrary nonsymmetric potential whose least value is attained at finitely many points.     

泵示功图单井自动量油技术研究

以井下泵示功图为基础,结合油井工况自动诊断技术,通过封闭曲线的曲率确定有杆抽油系统深井泵的游动阀、固定阀的开启点和关闭点,从而提出了有杆抽油系统单井自动量油的理论及其数学模型.经油田现场实测资料验证,以该理论为核心的泵示功图单井自动量油技术计算的产油量与实际产油量的平均相对误差为8.93%,最大相对误差为20.26%,最小相对误差为0.07%,相对误差在15%以内的井占85.71%.因此,利用该方法中封闭曲线的曲率来确定泵示功图的4个凡尔开闭点的方案是可行的,用于有杆抽油系统的单井自动量油具有实际的工程应用价值,该技术已应用于游梁式有杆抽油泵采油井自动监测系统中.     

INFLUENCE OF POLYMER CHARACTERISTICS AND MELT-SPINNING CONDITIONS ON THE PRODUCTION OF HIGH RANDOMNESS 60PHB/PET THERMOTROPIC LIQUID CRYSTAL COPOLYESTER FIBER

Six samples of linear high randomness 60PHB/ PET thermotropic liquid crystal copolyesters are made by melt copolymerization at 290℃ , whose randomness about 0.955 is measured by the discernible 'H-NMR spectrometer. High tenacity, high module fiber is prepared by melt spinning in liquid crystal phase. The effect of molecular weight, shear rate, temperature as well as spinning drawn ratio on the mechanical behavior of 60PHB / PET copolyester fiber are shown that, lower shear rate (2~ 10 s~(-1)), higher temperature melting (300℃ ), lower temperature spinning (280℃ ) and higher molecular weight are favourable to the increase of the fiber mechanical properties. With the variance of drawn ratio, fiber mechanical property has a transition point due to traversion from shear-orientation to drawn-orientation. The copolyester fiber has high crystallinity, high orientation at the crystalline region, high chain orientation and high regular fibrillar structure.     

像势对量子阱中类氢杂质结合能的影响

在有效质量近似下，利用变分方法研究了像势对量子阱中类氢杂质结合能的影响。计算中考虑到了阱和垒中电子有效质量的不同。数值计算结果表明：阱和垒中质量的不连续只对阱宽较窄的区域有影响，而像势则在整个区域都有影响．对于阱和垒中介电常数之比较大和阱宽较小的量子阱，考虑像势对阱中杂质结合能的修正是非常必要的     

Mössbauer Studies and Magnetic Properties of Y3−x Ce x Fe5O12

It is shown that in-situ ^166mHo (I = 7) in a spherical single crystal of HoF₃ can be used as sensitive internal thermometer to thermally detect NMR (NMR-TDNO) from the 100% abundant stable ¹⁶⁵Ho (I = 7/2) nuclei. In addition, new ^166mHo NMRON results are reported. Both the ^166mHo NMRON and ¹⁶⁵Ho NMR-TDNO spectra show three distinct quadrupolar split sub-resonances, in zero applied field. The data is used to make estimates of the Ho magnetic moments and quadrupole parameters for the ^166mHo and ^166mHo sites.     

Rashba polarization in HgCdTe inversion layers at large depletion charges

The Rashba effect in metal–insulator–semiconductor (MIS) structures based on zero-gap HgCdTe is investigated experimentally and theoretically over a wide doping range N_A–N_D=3×10¹⁵–3×10¹⁸ cm⁻³. Increase of doping enlarges the magnitude of the effect at the same 2D concentration and strengthens a gate-voltage dependence of the Rashba splitting. The results demonstrate values of Rashba polarization as high as P_R0.5 and a capability to control the Rashba effect strength at constant electron concentration.     

民生问题是构建社会主义和谐社会的根本

民生问题事关国家发展和社会进步之目标及动力，中国持续稳定发展必须不断改善民生。改善民生是一个涉及全局的系统工程，必须着力于走出一条新阶段的经济发展之路，建立合理的、有序的市场经济利益分配格局。