树的稳定子集和稳定指标

一个实矩阵的符号稳定性问题在经济学、生态学等诸多领域中都有应用背景．本文利用[1]中给出的不可约矩阵的符号稳定性的有关结论，将一个实矩阵的符号稳定性判定问题转化为一个等价的图论问题，即判定无向树中一个点子集的稳定性问题．本文引入了树的稳定子集的概念并给出了稳定子集的递归判别方法．本文还提出井研究了树的稳定指标，即树中所有稳定子集的最小基数，证明了关于稳定指标的一个min—max型定理，井给出了n阶树的稳定指标的最好上界及达到上界的极树的完全刻划。     

葡萄糖粉末的近红外光谱

糖尿病患者的自我监测是减少由糖尿病引发并发症的重要手段。无创血糖监测的近红外光谱分析方法是最具有应用前景的一种，葡萄糖近红外光谱则是研究无损血糖检测基础。本文通过实验采集了葡萄糖粉末的近红外光谱，并对结果作了详细分析。     

Influence of surface band gaps on the lifetimes of charge transfer states

Using a first principles electronic structure method, we investigate how a band gap in the surface projected density of states of a noble metal influences the resonant tunneling lifetime of an atomic level near the surface. Comparing Li atoms outside Cu(1 1 1), where the Li 2s level is within the gap, with Cu(0 0 1), where the Li 2s level is below the gap, reveals that the lifetime of the ionization level of Li is longer on Cu(1 1 1). This difference is caused both by the decreased final state phase space for the tunneling electron on Cu(1 1 1) and by a reduction in intra-atomic hybridization in Li outside a surface whose band gap encompasses the ionization level. Our results are consistent with previous experiments and theory that predict a similar trend for the ionization level of Cs above Cu(1 1 1) and Cu(0 0 1).     

Some applications of a cardinality estimate for a certain configuration

Two configurations are constructed and the cardinality of one of them is estimated in terms of that of the other. The estimate thus obtained is applied to certain combinatorial problems. Translated fromMatematicheskie Zametki, Vol. 63, No. 5, pp. 729–736, May, 1998.     

界面耦合对共聚物能带及键结构的影响

建立了紧束缚近似下的二嵌段共聚物-(A)x-(B)y-的物理模型,研究了组成共聚物的均聚物间界面相互作用-界面耦合的强弱对共聚体系的能带结构、键结构性质等的影响.共聚物的带隙也可通过改变均聚物之间的界面相互作用来加以调制,进一步发现可用界面势阱或能垒(energy barrier)来表征界面耦合的强弱.     

Band broadening evaluation by back-and-forth capillary electrophoresis

The purpose of this study is to develop a method for precise evaluation of band broadening in capillary electrophoresis. A capillary electrophoresis system with on-column twin detectors is constructed. Back-and-forth electrophoresis permits zones to make a round trip between the twin detectors placed at distant positions on the capillary. The system is capable of eliminating extra-column effects and discriminating between reversible and irreversible band-broadening mechanisms.     

Ferromagnetic ground state in the Kondo lattice model

We present a series of rigorous examples of the Kondo lattice model that exhibit full ferromagnetism in the ground state. The models are defined in one-, two- and three-dimensional lattices, and are characterized by a range of hopping terms, specific electron filling, and large ferromagnetic coupling. Our examples show that a sufficient strong but finite exchange coupling between conduction electrons and localized spins could overcome the competition from mobility of a finite density of electrons and drive the system from a paramagnetic phase to a ferromagnetic phase. We also establish a relation of ferromagnetism between the Hubbard model and Kondo lattice model. Meanwhile some rigorous results on ferromagnetism in the corresponding Hubbard model are presented. Received: 10 September 1997 / Revised: 15 October 1997 / Accepted: 17 October 1997     

Structures induced by collections of subsets: a hypergraph approach

During recent years, much attention has been paid by anthropologists and sociologists to the analysis of social networks. These networks arise from dyadic relationships such as kinship or friendship and they have been studied using techniques derived from graph theory. Although the study of such networks can cast much light on the social structure of a population, many important aspects of this structure cannot be addressed using dyadic relationships alone. For example, group membership gives rise to natural non-dyadic relationships which will be distorted if they are forced into a dyadic mold. The purpose of this paper is to propose an analytical scheme which will permit the study of structure induced by non-dyadic relationships. The concepts used derive from the theory of hypergraphs, and it is shown that these concepts permit a wide variety of structural questions to be posed.     

On the projectivity of threefolds

Let be a smooth complete three-dimensional algebraic variety (defined over an algebraically closed field ). We show that is projective if it contains a divisor which is positive on the cone of effective curves.