产生暗归零码光标记信号的新方案

在对预编码、调制和编码过程进行改进的基础上,提出了一种利用一个双臂马赫-曾德尔铌酸锂调制器和一个电信号时延器产生可调占空比和消光比的光暗脉冲归零码二进制信号的新方案。实验证明这种信号能用传统的二进制强度调制-直接检测系统的接收机进行检测。实验得到了在调节电信号时延器时速率为2.5 Gbit/s的光暗脉冲归零码二进制信号的频谱变化规律,以及占空比分别为0.25,0.35,0.60和0.80时光暗脉冲归零码二进制信号的误码率和眼图。此外,利用该方案产生的光暗脉冲归零码二进制信号可以作为标记在光标记交换网络中得到应用。     

横向随机晶场Ising模型的相图和磁化行为研究

在有效场理论和切断近似框架内，选择自旋S=1的二维方格子，研究横向随机晶场Ising模型的相图和磁化行为，重点是横向随机晶场浓度和晶场比率对相图和磁化的影响.给出了i>T-D_x空间的相图和m-T空间的磁化图.在晶场稀疏情况下，负晶场方向存在临界温度的峰值，正方向可出现重入现象.晶场比率取+0.5和-0.5时，磁有序相范围缩小，特别是晶场比率取-0.5时，随晶场浓度的降低，临界温度峰值从横向晶场负方向渡越到正方向.固定某一负晶场值，不同晶场比率的磁化行为有明显差异.同时与纵向稀疏晶场Ising模型结果进行有意义的比较. 关键词： 横向随机晶场Ising模型 相图 磁化行为     

More on Geometries of the Fischer Group Fi 22

We give a new, purely combinatorial characterization of geometries with diagram identifying each under some natural conditions—but not assuming any group action a priori—with one of the two geometries and related to the Fischer 3-transposition group Fi ₂₂ and its non-split central extension 3 · Fi ₂₂, respectively. As a by-product we improve the known characterization of the c-extended dual polar spaces for Fi ₂₂ and 3 · Fi ₂₂ and of the truncation of the c-extended 6-dimensional unitary polar space.     

Conformational phase diagram of poly(l-lysine) in sodium alkanesulfonate aqueous solutions at various temperatures

The conformation of poly(l-lysine) (PLL) was investigated in sodium alkanesulfonate C_nSO₃Na (n=8, 7) at various temperatures by circular dichroism spectrum measurements. C₈SO₃Na induced a double-step conformational change from a coil, to a β-sheet, and then to an α-helix, in which C₇SO₃Na induced a single-step coil-to-helix conformational change. Binding isotherms of C₈SO₃Na by PLL were constructed from the potentiometry of equilibrium concentration of the surfactant using a surfactant ion-selective electrode. The curves indicated the cooperative binding characteristic and were analyzed by a linear lattice model using the Bethe approximation. The thermodynamic parameters obtained from the model revealed that the binding of C₈SO₃Na by PLL was an entropy-driven process. The conformational change was observed at nearly full binding, presumably due to the surfactant clustering of the ordered conformation.     

Rigidity of Coxeter Groups and Artin Groups

A Coxeter group is rigid if it cannot be defined by two nonisomorphic diagrams. There have been a number of recent results showing that various classes of Coxeter groups are rigid, and a particularly interesting example of a nonrigid Coxeter group has been given by Bernhard Mühlherr. We show that this example belongs to a general operation of diagram twisting. We show that the Coxeter groups defined by twisted diagrams are isomorphic, and, moreover, that the Artin groups they define are also isomorphic, thus answering a question posed by Charney. Finally, we show a number of Coxeter groups are reflection rigid once twisting is taken into account.     

Subsolidus Phase Equilibria in the System CaO-Al2O3-CoO and the Crystal Structure of Novel Ca3CoAl4O10

The subsolidus phase diagram, CaO-Al₂O₃-CoO, and its phase relations below 1300°C have been studied in air. The stability regions of nine subsolidus compatibility triangles were established and a new ternary phase was found. The structure of this compound, Ca₃CoAl₄O₁₀ (orthorhombic, space group Pbc2₁, a=5.1452(2) Å, b=16.7731(5) Å, c=10.7055(3) Å), was determined from X-ray diffraction data and found to be isostructural with Ca₃ZnAl₄O₁₀. This is an open framework compound with three crystallographically different channels, each with a diameter of ∼3.5 Å. The two end members of the binary CoO-CaO system are surrounded by small regions of solid solutions. Lab color parameters were measured in several compositions. No ternary phases were found when Co was substituted by other divalent cations such as Sr, Ba, Mn, Ni, Cu, Cd, Sn and Pb.     

A Geometric Characterization of Fischer's Baby Monster

The sporadic simple group F ₂ known as Fischer's Baby Monster acts flag-transitively on a rank 5 P-geometry . P-geometries are geometries with string diagrams, all of whose nonempty edges except one are projective planes of order 2 and one terminal edge is the geometry of the Petersen graph. Let be a flag-transitive P-geometry of rank 5. Suppose that each proper residue of is isomorphic to the corresponding residue in . We show that in this case is isomorphic to . This result realizes a step in classification of the flag-transitive P-geometries and also plays an important role in the characterization of the Fischer–Griess Monster in terms of its 2-local parabolic geometry.     

Critical behavior and interfacial tension of mixtures of propylene glycol and ethylene glycol oligomers

This investigation presents an analysis of the critical behavior of mixtures of oligomers of propylene glycol, PG₁₇, and ethylene glycol, EG_n, withn=3, 4, 5, 6.4, 8.7, 12.1 and 22.1. The critical coordinates, _c andT _c were determined from the phase diagrams. The critical compositions compare very well with the Huggins-Flory predictions. The interaction parameter _n is around one for EG₃, EG₄ and EG₅ and it increases up to two for the higher oligomers. The break in the interaction parameter also corresponds to a minimum in the critical temperature. The phase diagrams and the interfacial tension were used to get the critical exponents and , respectively. The data were analysed with two approaches. First, from the temperature dependence of the length of the tie-lines and of the interfacial tension up to the upper critical solution temperature, UCST. Second, with the data at 30°C using the critical temperature of the systems as the variable. The first method led to =0.39±0.05 in good agreement with the result of the second method, =0.37±0.04. The exponents for the interfacial tension, , determined with the first method for PG₁₇ with EG_6.4, EG_8.7 and EG_12.1 are =1.66±0.11, 1.46±0.25 and 1.73±0.18, respectively. The second method led to =1.17±0.14. The critical exponents are compared to mean field and ising-3D predictions.     

Mg-Sm体系相图及其Sm2Mg13金属间化合物的研究

本文借助于化学分析、X射线衍射、差热分析、金相和电子探针研究了Mg-Sm二元相图。发现并测定了金属间化合物,Sm_2Mg_(13)它属正交晶系,晶胞参数a=13.855(?)、b=9.357、c=7.457(?)。z=2,v=966.7(?)~3,dx=2.118克/厘米~3(Dobs=2.127克/厘米~3)。并得到一套衍射图谱。同时发现Mg-Sm二元体系有二个共晶反应,一个类共晶反应,三个化合物分解反应和三个多晶转变。     

Dynkin Diagram Classification of λ-Minuscule Bruhat Lattices and of d-Complete Posets

d-Complete posets are defined to be posets which satisfy certain local structural conditions. These posets play or conjecturally play several roles in algebraic combinatorics related to the notions of shapes, shifted shapes, plane partitions, and hook length posets. They also play several roles in Lie theory and algebraic geometry related to -minuscule elements and Bruhat distributive lattices for simply laced general Weyl or Coxeter groups, and to -minuscule Schubert varieties. This paper presents a classification of d-complete posets which is indexed by Dynkin diagrams.