Numerical and experimental research on annular crossed cable-truss structure under cable rupture

The Annular Crossed Cable-Truss Structure（ACCTS） is a new type of Tensile Spatial Structure with a configuration suitable to cover large-span stadiums. Its configuration has potential to perform well in resisting disproportionate collapse. However, its disproportionate collapse resistance hasn＇t yet been analyzed in depth. In this study, numerical and experimental research was carried out to investigate the performance of ACCTS under cable rupture. The numerical analysis was done for ten cable-rupture plans using LS-DYNA（explicit method） and the experimental test on an ACCTS with a diameter of 17.15 m was performed for three cable-rupture plans. It is concluded that, while deflections increase with the number of removed cables, an ACCTS does not undergo a disproportionate collapse and it provides a promising structural concept for tensile spatial structures.

Synthesis and Crystal Structure of {Cu_2(pdc)_2(4,4'-bipy)(H_2O)·3H_2O}_2

The title compound {Cu2(pdc)2(4,4?-bipy)(H2O)3H2O}2 1 (H2pdc = pyridine-2,6- dicarboxylic acid, also known as dipicolinic acid; 4,4?-bipy = 4,4?-bipyridine) has been synthesized by the hydrothermal reaction and its structure was determined by single-crystal X-ray diffraction. The crystal is of triclinic, space group Pi with a = 7.2278(3), b = 10.6259(4), c = 17.7614(6) ? a = 79.5990(10), = 83.6300(10), ? = 71.8280(10)o, V = 1272.60(8) ?, C48H44Cu4N8O24, Mr = 1371.07, Z = 1, Dc = 1.789 g/cm3, = 1.747 mm-1, F(000) = 696, R = 0.0397 and wR = 0.1137 for 3938 observed reflections (I > 2s(I)). There are two kinds of Cu coordination environments, and each central copper(II) atom is five-coordinated in a distorted square-based pyramidal coordination geo- metry. Four copper(II) atoms are linked by four pdc and two 4,4?-bipy ligands to form an annular rectangle structure. Extensive hydrogen-bonding interactions involving carboxylate O atoms as well as coordinated and free water molecules lead to the formation of a three-dimensional network struc- ture.

Microwave transmittance characteristics in different uniquely designed one-dimensional plasma photonic crystals

Plasma photonic crystals(PPCs)are emerging as a powerful instrument for the dynamical control of the electromagnetic properties of a propagating wave.Here we demonstrate several one-dimensional(1 D)PPCs with uniquely designed superlattice structures,annular structures or with incorporation of the third material into the primitive unit cell.The influences of the properties of the third material as well as the structural configurations of suplerlattices on the transmittance characteristics of PPCs have been investigated by use of the finite element method.The optimal design strategy for producing PPCs that have more and larger band gaps is provided.These new schemes can potentially be extended to 2 D or 3 D plasma crystals,which may find broad applications in the manipulation of microwaves and terahertz waves.

Physical model for acoustic resonance in annular cavity structure

A physical model for acoustic resonance in the annular cavity structure is developed to represent the typical characteristic when acoustic resonance occurs.Firstly,the measurement of sound pressure in the casing and rotor blades vibration is operated in a multistage high pressure compressor.The sharp peak frequency and discrete multi-tone occur in the frequency spectrum of sound pressure in the compressor,and the vibration of the first stage of rotor blades synchronously presents the high amplitude.The frequencies associated with rotor blades vibration can be calculated with rotating sound source theory.It is also confirmed that acoustic resonance occurs in the multistage compressor.With acoustic similarity principle,an annular cavity model is established to simulate the typical characteristics of acoustic resonance in the compressor based on Large Eddy Simulation(LES)and Lighthill acoustic analogy.The coupling relationship between cavity acoustic mode and disc vibration mode shape is expounded when acoustic resonance occurs in the model.And acoustic resonance will be locked in the certain flow rate range.All these characteristics match well with those occur in the multistage high pressure compressor.