Synthesis and One-dimensional Structure of Cobalt(Ⅱ) Complex [(NaOC_2H_5)CoL_2]_n

The treatment of bis(2-hydroxybenzyl)-amine(HL) with NaOH and Co(Ⅱ)(NO) 2 gives isostructural one-dimensional coordination polymers [(NaOC2H5)CoL2]n(1). The cobalt ions have an octahedral geometry and are coordinated by two crystallographically independent ligands which are further linked by μ -O\-\{phenol\} bridged Co and Na atoms to give a one-dimentional structure.

Synthesis, Characterization and Crystal Structure Determination of a Thiocyanato Bridged One-dimensional Polymeric Complex of Cadmium(Ⅱ)

A new one-dimensional polymeric complex [Cd（SCN）2（H2O）]L （L = N,N′-bis（furan- 2-ylmethylene）hydrazine） has been synthesized and characterized by IR, UV spectra, TG-DTA technique and single-crystal X-ray diffraction analysis. It crystallizes in triclinic, pace group P1^- with a = 5.9268（8）, b = 10.8678（15）, c = 13.3671（19） A, α = 109.295（2）, β = 95.092（2）, γ = 97.8580（10）°, V = 796.70（19）A^3, Z = 2, C12H10CdN4O3S2, Mr = 434.76, μ = 1.648 mm^-1, Dc = 1.812 g/cm^3, F（000） = 428, R = 0.0308 and wR = 0.0769. The crystal structure reveals that the structure of [Cd（SCN）2（H2O）]n features di-μ-1,3-thiocyante bridges and 1D chains. The octahedrally coordinated Cd atom is surrounded by one oxygen atom from water molecule, three S atoms and two N atoms from five di-μ-1,3 thiocyanato bridges. The Cd atoms are connected by two di-μ-1,3 thiocyanato bridges with the Cd（1）…Cd（1A） separation of 4.239（1） A and Cd（1）...Cd（1B） of 5.852（1）/~. In addition, the one-dimensional straight chain structure is further connected by multiform intermolecular N-H…O hydrogen bonds and π-π interactions to form a three-dimensional supramolecular structure.

ELASTIC WAVE LOCALIZATION IN TWO-DIMENSIONAL PHONONIC CRYSTALS WITH ONE-DIMENSIONAL QUASI-PERIODICITY AND RANDOM DISORDER

The band structures of both in-plane and anti-plane elastic waves propagating in two-dimensional ordered and disordered （in one direction） phononic crystals are studied in this paper. The localization of wave propagation due to random disorder is discussed by introducing the concept of the localization factor that is calculated by the plane-wave-based transfer-matrix method. By treating the quasi-periodicity as the deviation from the periodicity in a special way, two kinds of quasi phononic crystal that has quasi-periodicity （Fibonacci sequence） in one direction and translational symmetry in the other direction are considered and the band structures are characterized by using localization factors. The results show that the localization factor is an effective parameter in characterizing the band gaps of two-dimensional perfect, randomly disordered and quasi-periodic phononic crystals. Band structures of the phononic crystals can be tuned by different random disorder or changing quasi-periodic parameters. The quasi phononic crystals exhibit more band gaps with narrower width than the ordered and randomly disordered systems.

Directional Propagation Characteristics of Flexural Waves in Two-Dimensional Thin-Plate Phononic Crystals

The propagation characteristics of flexural waves in two-dimensional thin-plate phononic crystals （PCs） are analysed with the plane wave expansion （PWE） method to yield phase constant surfaces, which predict high directivity of flexural wave propagation for certain frequencies outside the band gap. The prediction is validated through the computation of the harmonic responses of a finite structure with 9 × 9 unit cells. The results indicate that directional propagation of flexural waves is an while specific effects of the directional propagation in inherent characteristic of two-dimensional thin-plate PCs a finite structure vary with the positions of excitations.

Synthesis and Characterization of a Lead(Ⅱ) Complex with Microporous Structure

A 3-D coordination polymer [PbNH(CH2COO)2] 1 has been prepared under hydrothermal conditions and its crystal structure was studied by single-crystal X-ray diffraction. The compound belongs to orthorhombic system, space group Fdd2 with unit cell parameters: a = 13.6304(6), b = 36.295(1), c = 5.0821(2) ? V = 2514.19(17) 3, Z = 16, Mr = 338.28, Dc = 3.575 g/cm3, F(000) = 2400 and m(MoKa) = 2.679 cm-1. The final R and wR are 0.0290 and 0.0685, respectively, for 874 observed reflections with I > 2s(I). The lead has a distorted tetragonal pyramid environment with four oxygen donors in the basal plane and one nitrogen donor in the axial site. Micro-channels are observed in the neutral 3-D network of 1.

Nonreciprocal properties of 1D magnetized plasma photonic crystals with the Fibonacci sequence

In this paper, the nonreciprocal properties of a novel kind of 1D magnetized plasma photonic crystals(MPPCs) with the Fibonacci sequence are investigated. The isolation of the proposed 1D MPPCs is also used to analyze the nonreciprocal properties. Compared to the conventional 1D MPPCs with periodic structure, the nonreciprocal performance can be significantly improved.The effects of several parameters of the proposed 1D MPPCs on the nonreciprocal properties are studied by the transfer matrix method, which includes the incident angle, order of the Fibonacci sequence, plasma frequency, plasma cyclotron frequency and plasma filling factor. The obtained results show that the nonreciprocal propagation properties can be improved by increasing the values of the plasma cyclotron frequency and incident angle, but they will worsen by blindly increasing the order of the Fibonacci sequence, plasma frequency and filling factor of plasma.The peaks of transmittance also are obviously reduced. In addition, the value of isolation will increase with increasing the incident angle, order of Fibonacci sequence, plasma frequency and plasma filling factor. However, when the plasma cyclotron frequency is increased, the value of isolation will be increased at lower frequencies, but is almost unchanged at higher frequencies.

Photonic Band Modulation in a Two-Dimensional Photonic Crystal with a One-Dimensional Periodic Dielectric Background

A two-dimensional photonic crystal with a one-dimensional periodic dielectric background is proposed. The photonic band modulation effects due to the periodic background are investigated based on the plane wave expansion method. We find that periodic modulation of the dielectric background greatly alters photonic band structures, especially for the E-polarization modes. The number, width and position of the photonic band gaps （PBGs） sensitively depend on the structure parameters （the layer thicknesses and dielectric constants） of the one-dimensional periodic background,

Fault-Tolerant Resolvability of Certain Crystal Structures

An ordered set W of vertices of a graph G is called a resolving set, if all the vertices of G are uniquely determined by the vector of distances to the vertices in W. The metric dimension of G is the minimum cardinality of a resolving set of G. A resolving set W for G is fault-tolerant if W\{v} is also a resolving set, for each v in W, and the fault-tolerant metric dimension of G is the minimum cardinality of such a set. In this paper we determine the metric dimension and fault-tolerant metric dimension problems for the graphs of certain crystal structures.

CRYSTAL STRUCTURE OF A LONG－PERIOD ORDERED PHASE IN Fe－C MARTENSITE AND COMPUTER SIMULATION OF ITS ELECTRON DIFFRACTION PATTERNS

Different structure models of a long-period ordered phase in Fe-C martenstie formed during aging have been checked by computer simulation of electron diffraction(ED) patterns based on these models.The results showed that the simulated ED pattern of γ'-FexC(Ⅱ) model proposed by the present authors is in good agreement with experimentally observed ED pattern.It was also confirmed that the incommensurate superperiod stems from the coexistence of several γ'-Fe_xC(H) phases with different superperiods.The Fe(144)C(24)(Fe6C) model proposed by Uwakweh et al.generated ED patterns remarkably different from the experimental ones.

Study of periodic band gap structure of the magnetized plasma photonic crystals

The characteristics of the periodic band gaps of the one dimension magnetized plasma photonic crystals are studied with the piecewise linear current density recursive convolution (PLCDRC) finite-differential time-domain (FDTD) method. In frequency-domain, the transmission coefficients of electromagnetic Gaussian pulses are computed, and the effects of the periodic structure constant, plasma layer thickness and parameters of plasma on the properties of periodic band gaps of magnetized photonic crystals are a...

Band Structure Characteristics of Two-Dimensional Si-A (Ge, Pb, Sn) Alloy-Air Holes Thermal Crystals

This paper designs the thermal crystals composed of alloy materials with air holes and analyzes their properties of band structures,heat transmission,and flux spectra.Thermal crystals composed of Si-A(A=Ge,Sn,Pb)alloys as background materials and air holes with square array are used to construct an elastic-constant periodic structure and their high-frequency phononic band is calculated by deploying finite element methods.Moreover,this paper investigates heat transmission through a finite array of thermally excited phonons and presents the thermal crystal with maximum heat transport.The results show that a wider bandgap could be achieved by increasing the air hole radius and decreasing the lattice constant.In the alloy materials,with increasing atomic radius and thus atomic mass(Ge,Sn,Pb),the frequency range(contributed to thermal conductivity)shifts towards lower frequency.Hence,the bandgap frequencies also shift toward low frequency,but this decreasing rate is not constant or in order,so former may have a faster or slower decreasing rate than the later.Thus,the frequency range for the contribution of heat transportation overlaps with the bandgap frequency range.The development of thermal crystals is promising for managing heat and controlling the propagation of the thermal wave.

Band structure properties of elastic waves propagating in the nanoscaled nearly periodic layered phononic crystals

The localization factor is used to describe the band structures for P wave propagating normally in the nanoscaled nearly periodic layered phononic crystals. The localization factor is calculated by the transfer matrix method based on the nonlocal elastic continuum theory.Three kinds of nearly periodic arrangements are concerned, i.e., random disorder, quasiperiodicity and defects. The influences of randomly disordered degree of the sub-layer＇s thickness and mass density, the arrangement of quasi-periodicity and the location of defect on the band structures and cut-off frequency are analyzed in detail.

周期结构波阻板的隔振效应及其影响因素研究

针对动力机器、交通荷载(地铁、高铁、轻轨等)以及建筑施工过程(爆破、打桩、强夯等)诱发的振动污染问题,基于声子晶体带隙理论,提出一种周期结构波阻板隔振结构。研究周期结构波阻板隔振效果,并与理论计算所得带隙进行对比;探讨埋置深度、结构布置等因素对周期结构波阻板隔振性能的影响。结果表明:30~50 Hz频带范围内振动加速度大幅衰减,趋近于0;与所得带隙频率范围相比,变化规律基本一致;同等条件下,布置周期结构波阻板后监测点处的竖向加速度幅值显著降低,衰减幅度为57.6%,隔振性能优于传统波阻板;并且通过合理设计埋置深度、布置层数、每层周期数等参数,可使周期结构波阻板的振动控制性能和效果均显著提升。

Dimensionality Reducing from Three-dimensional RbLu5Te8 to Two-dimensional CsMnGdTe3:Syntheses,Crystal and Electronic Structures

Two new rare-earth metal chalcogenides,namely RbLu5Te8 and CsMnGdTe3,have been successfully synthesized under high-temperature solid-state reaction conditions and structurally characterized by single-crystal X-ray diffraction analysis.RbLu5Te8 belongs to the monoclinic space group C2/m(no.12)with two formula units in a unit cell:a=22.075(5),b=4.2987(8),c=10.588(2)A,β=103.89(2)°,V=975.4(4)A3,whereas CsMnGdTe3 crystallizes in the orthorhombic space group Cmcm(no.63)with four formula units in a unit cell:a=4.4872(8),b=16.769(3),c=11.807(2)A and V=888.4(3)A3.In the structure of RbLu5Te8,face-,edgeand vertex-sharing[LuTe6]octahedra are interconnected to produce a three-dimensional(3D)framework with Rb^+lying in the tunnels.The crystal structure of CsMnGdTe3 consists of two-dimensional(2D)[MnGdTe3]^–layers of edge-and vertex-sharing[GdTe6]octahedra with Mn atoms filling the tetrahedral interstices,which stack along the b-axis.The Cs atoms are located between the[MnGdTe3]^–layers and surrounded by eight Te atoms to form a[CsTe8]bicapped trigonal prism.Moreover,theoretical studies have aided the understanding of their electronic structures.

Holes Effects in Plane Periodic Multilayered Viscoelastic Media

This work deals with the study of the reflection and transmission properties of plane periodic structures composed of N periods (1 ≤ N ≤ 3) in the MHz frequency range. The period consists of two bounded plates presenting a high acoustic impedance contrast one of which is in aluminum, the other is in polyethylene. The longitudinal and transversal attenuations are considered in polyethylene and neglected in aluminum. We take into account the case of emerging holes in the polyethylene layer. Simulations are based on the stiffness matrix method (SMM) developed by Rokhlin. When attenuation is considered in polyethylene, the reflection coefficients are different depending on the insonification side. The comparison of results without or with holes configurations are performed and showed that throughout holes allow the rapid observation of forbidden bands. The attenuation of the whole multilayer is also determined.

恒频声学二极管的设计及特性研究

声学二极管能控制声波仅在一个方向有效传输在反方向无法传播,在通信技术中具有广泛的应用,然而目前大多数的声学二极管设计是基于非线性效应使系统只通过新的高次频率并阻止原频率的传输.本文利用不对称结构与弱非线性声子晶体的组合,提出了一种一维声二极管模型,实现弹性波的不对称传输,并保持频率不变.该模型由左端的变幅杆和右端的非线性弹簧质量链组成,理论分析表明,该声学二极管具有与电子二极管相同的正向和反向特性,并通过有限元仿真验证了该模型的有效性.

具有光子晶体结构的电致变色器件的研究进展

光子晶体(Photonic crystals,PCs)是一种周期性排列有序的微结构材料,由于具有独特的周期结构、灵活的光调控能力等特点被广泛应用于电致变色(Electrochromicsm,EC)领域。具有光子晶体结构的电致变色器件可利用其产生的结构色与电致变色的化学色相结合,进而丰富和拓展器件的色域,为电致变色的色彩调控提供新的策略。此外,多维光子晶体结构可以为电致变色器件(Electrochromic devices,ECDs)提供有序离子传输通道和多离子活性反应位点,促进离子的注入/脱出,从而提升器件的电致变色性能。本文扼要介绍了评价电致变色材料与器件性能的参数,着重归纳了不同维度光子晶体在电致变色领域的应用策略,并详细总结了具有光子晶体结构的电致变色器件在智能窗、显示、伪装等领域的潜在应用。最后,针对目前光子晶体结构在电致变色领域中仍存在的问题,对其未来的发展趋势进行了展望。

周期管路系统的振动特性研究

管路系统广泛应用于船舶动力、海洋工程、建筑环境等领域,其振动噪声可能会导致设备的失效与破坏。具有弹性波带隙特征的周期性结构设计可在特定频段内实现波的人为调控,有效降低管路结构的低频振动噪声。将周期结构引入一维管路系统,基于布拉格散射和局域共振2种带隙机理,设计具备全频段良好减振性能的周期管路结构。结合传递矩阵法和有限元法,计算了布拉格型管路的能带结构与减振特性。建立引入局域共振单元的周期管路系统有限元模型,计算并分析晶格常数、周期数量、局域振子尺寸等参数对周期管路结构振动特性的影响规律。结果表明,基于声子晶体带隙特性设计的周期管路系统具有优良的减振性能。

二维周期排桩隔振技术应用于兰州中川国际机场的初探研究

为了克服传统隔振技术因需要在基础与地基之间埋置隔振装置从而削弱结构的整体性和限制隔振装置的更换等方面的不足,立足于屏蔽弹性波的新思想,基于周期结构的通禁带,采用数值模拟手段研究二维周期排桩结构的带隙特性及其对禁带频段内弹性波的抑制作用,并探讨将这种隔振新技术应用在兰州中川国际机场的新建航站楼与跑道之间来实现隔振时结构设计参数的选取规律。研究发现,对于相对刚度而言,在所选择的材料中,外层散射体钢和内层散射体混凝土及土体所组成的胞元具有最宽的弹性波衰减范围;减小晶格常数增大填充率或者构造含有两种晶格常数的胞元结构可获得更宽的弹性波衰减范围。研究结果可为中川国际机场的周期性排桩设计提供理论指导,从而精准地实现工程结构物的隔振需求。