Uncommon suffix tries

Common assumptions on the source producing the words inserted in a suffix trie with n leaves lead to a height and saturation level. We provide an example of a suffix trie whose height increases faster than a power of n and another one whose saturation level is negligible with respect to . Both are built from VLMC (Variable Length Markov Chain) probabilistic sources and are easily extended to families of tries having the same properties. The first example corresponds to a “logarithmic infinite comb” and enjoys a non uniform polynomial mixing. The second one corresponds to a “factorial infinite comb” for which mixing is uniform and exponential. © 2013 Wiley Periodicals, Inc. Random Struct. Alg., 46, 117–141, 2015     

Stability criteria in terms of two measures for functional differential equation with variable‐time impulses

This paper focuses on the stability in terms of two measures for functional differential equation with variable‐time impulses. Being different from most of existing literatures, the impulses of functional differential equation are assumed to be closely associated to the current state. We propose a new comparison principle for the considered systems and establish several stability criteria in terms of two measures. Also, the theoretical results are applied in a class of delayed neural network systems with variable‐tine impulses, and numerical simulations are introduced to illustrate the effectiveness of our results. Copyright © 2014 John Wiley & Sons, Ltd.     

In situ single‐crystal to single‐crystal (SCSC) transformation of the one‐dimensional polymer catena‐poly[[diaqua(sulfato)copper(II)]‐μ2‐glycine] into the two‐dimensional polymer poly[μ2‐glycine‐μ4‐sulfato‐copper(II)]

The one‐dimensional coordination polymer catena‐poly[diaqua(sulfato‐κO)copper(II)]‐μ₂‐glycine‐κ²O:O′], [Cu(SO₄)(C₂H₅NO₂)(H₂O)₂]_n, (I), was synthesized by slow evaporation under vacuum of a saturated aqueous equimolar mixture of copper(II) sulfate and glycine. On heating the same blue crystal of this complex to 435 K in an oven, its aspect changed to a very pale blue and crystal structure analysis indicated that it had transformed into the two‐dimensional coordination polymer poly[(μ₂‐glycine‐κ²O:O′)(μ₄‐sulfato‐κ⁴O:O′:O′′:O′′)copper(II)], [Cu(SO₄)(C₂H₅NO₂)]_n, (II). In (I), the Cu^II cation has a pentacoordinate square‐pyramidal coordination environment. It is coordinated by two water molecules and two O atoms of bridging glycine carboxylate groups in the basal plane, and by a sulfate O atom in the apical position. In complex (II), the Cu^II cation has an octahedral coordination environment. It is coordinated by four sulfate O atoms, one of which bridges two Cu^II cations, and two O atoms of bridging glycine carboxylate groups. In the crystal structure of (I), the one‐dimensional polymers, extending along [001], are linked via N—H...O, O—H...O and bifurcated N—H...O,O hydrogen bonds, forming a three‐dimensional framework. In the crystal structure of (II), the two‐dimensional networks are linked via bifurcated N—H...O,O hydrogen bonds involving the sulfate O atoms, forming a three‐dimensional framework. In the crystal structures of both compounds, there are C—H...O hydrogen bonds present, which reinforce the three‐dimensional frameworks.     

变截面钢管混凝土格构柱轴压极限承载力

变截面钢管混凝土格构柱的轴压试验结果表明,随着试件高度的增大和柱肢坡度的减小,其极限荷载逐渐降低.基于上述规律,在等截面钢管混凝土格构柱计算框架的基础上,研究了变截面钢管混凝土格构柱轴压极限承载力的计算方法.提出变截面钢管混凝土格构柱等效长度的概念和等效长度法的计算公式,其承载力计算结果与试验结果吻合良好.最后在有限元数值分析验证的基础上,给出适合工程应用的四肢变截面钢管混凝土格构柱轴压极限承载力的实用算法,为钢管混凝土设计规程的进一步完善提供参考.     

解析角变量量子化的困难

目的分析量子力学中角变量量子化的困难。方法采用列举,分析及归纳法进行论证。结果角变量量子化遇到难以解决的困难。结论在现有量子理论基础上,角变量量子化无法解决。     

三维钴基MOF[KCo7(OH)3(ip)6(H2O)4]·12H2O作为超级电容器的高容量电极材料

为了开发较高能量密度的超级电容器,我们通过简单的溶剂热反应合成了一种三维的钴基金属有机框架(MOF)化合物([KCo7(OH)3(ip)6(H2O)4]·12H2O,Co?ip;ip=间苯二甲酸根),并考察了其作为超级电容器电极材料的性能。Co?ip电极显示出高比电容、良好的循环稳定性和优良的倍率性能。在1 mol·L^-1 KOH溶液中,电流密度为1 A·g^-1时,其最大比电容为1660 F·g^-1。在电流密度为2 A·g^-1条件下,循环3000次后,其比电容的保持率为82.7%。优异的超级电容性能可归因于Co?ip具有纳米尺寸颗粒和三维的多孔结构。     

Development of variable‐magnification X‐ray Bragg optics

A novel X‐ray Bragg optics is proposed for variable‐magnification of an X‐ray beam. This X‐ray Bragg optics is composed of two magnifiers in a crossed arrangement, and the magnification factor, M, is controlled through the azimuth angle of each magnifier. The basic properties of the X‐ray optics such as the magnification factor, image transformation matrix and intrinsic acceptance angle are described based on the dynamical theory of X‐ray diffraction. The feasibility of the variable‐magnification X‐ray Bragg optics was verified at the vertical‐wiggler beamline BL‐14B of the Photon Factory. For X‐ray Bragg magnifiers, Si(220) crystals with an asymmetric angle of 14° were used. The magnification factor was calculated to be tunable between 0.1 and 10.0 at a wavelength of 0.112 nm. At various magnification factors (M≥ 1.0), X‐ray images of a nylon mesh were observed with an air‐cooled X‐ray CCD camera. Image deformation caused by the optics could be corrected by using a 2 × 2 transformation matrix and bilinear interpolation method. Not only absorption‐contrast but also edge‐contrast due to Fresnel diffraction was observed in the magnified images.     

Core‐Shell Structured Layered Lanthanide‐Organic Complexes with Stilbazolium‐type Dye Encapsulation for Multifunctional Performances

Host‐guest encapsulation of functional organic dye into a porous metal‐organic framework can give rise to the development of new functional materials. In this work, by intercalating the stilbazolium‐type dye (DEAST)I (4′‐diethylamino‐N‐methyl stilbazolium) into four lanthanide layered metal‐organic complexes (Ln‐LMOCs), i. e. {[Ln(BTB)(H₂O)₂]?3(DMF)?2(H₂O)}_n (Ln=La (1), Nd (2), Sm (3), Er (4)), four responsive (DEAST)I@Ln‐LMOC composites have been prepared, serving as multifunctional performance platform. The core–shell structures of (DEAST)I@Ln‐LMOC composites have been fully characterized by IR, UV/Vis, PXRD, SEM, TEM, TGA and ESR. Significantly, after intercalation of dyes, the (DEAST)I@Ln‐LMOC composites exhibit enhanced luminescent sensing properties in detecting Fe³⁺ with much higher water stabilities. The luminescent sensing behavior stems from the fluorescence resonance energy transfer (FRET) from the π‐electron‐rich BTB ligands to the Fe³⁺, and their higher water stabilities are induced by electrostatic interactions and lower porosity. Specially, the characteristic emissions of Sm³⁺ will not be affected after the encapsulation guest dyes, which provide a theoretical guide for the modulation of luminescence devices. Finally, better ion conductivities and diminished photocurrents can be achieved after the embedding of the functional organic dye. In all, the formation of (DEAST)I@Ln‐LMOC composites with core–shell structures can be utilized as a multifunctional platform with good stability.     

供热空调系统并联变频水泵转速比配置优化分析

建立了供热空调系统中变频水泵扬程、效率和功率与流量和转速间的关联模型．结合并联水泵的运行特性,以最佳点工作流量与水泵转速比范围为参考,理论分析了对应并联变频水泵电耗极小值运行工况下各水泵转速比配置情况．以采取变压差设定值控制的某交流量空调水系统并联水泵运行工况为算例,仿真研究了一台水泵全速运行、一台水泵变频运行,两台水泵同步变频运行且转速比相差0．05,两台水泵同步变频运行且转速比相差0．1与两台水泵同步变频运行且转速比相同4种控制方案的水泵节能效果．理论分析与仿真结果表明,并联水泵转速比的差异将导致一台水泵或多台水泵效率低下,当各水泵转速比相同时,并联水泵的总电耗最小．     

昆翅在飞行中的动态形变

通过理论模化途径研究昆翅在飞行中的动态形变机制.设计翅气动力试验平台,验证翅准静态形变影响气动力的"柔性楔形效应"理论解释.探讨昆翅的变刚度特性表明,弦向刚度分布规律符合二项式函数时具有优越性和现实性,进而指出昆姻结构的变刚度特性是产生高升力的基本条件.建立了柔性翅的简化力学模型,通过坐标变换法求解在气动力和惯性力共同...