Abstract: A computer-aided time reversal process (CTRP) is proposed for the structural damage diagnosis. In the standard time reversal process (STRP), both forward and backward processes are conducted by the measurement. However, in the proposed CTRP, the forward process is conducted by the measurement while the backward process is conducted by the computation. As a benefit of the computer-based backward process, the unwanted Lamb wave modes which do not carry damage information can be readily removed from the signals reconstructed at the input excitation point. The reconstructed signals refined in such a way can make the signal processing for the damage diagnosis more efficient and easier.
Abstract: The results on a numerical and experimental study of graphite/epoxy composite plates [03/903]S are presented. Each specimen was firstly impacted by the low velocity with different energy level. Compression experiment based on carrier electronic speckle pattern interferometry (carrier-ESPI) is made for the post-impact composite plate. The finite element method (FEM) is used to gain further understanding of the deformation behavior of impacted specimens. The compressive deformation of various delaminated composite plates are analyzed with software ANSYS to see that the impact parameters and delamination damage data, such as impact energy, maximum impact force and delamination area, affect the deformation fields. In addition, the comparisons between the finite element results and experimental measurements are considered under different compression loads.
Abstract: This paper analyzes the reasons for delamination of ceramsite aggregate concrete mixture, obtained influencing factors of working performance based on the study of equations of lightweight aggregate motion. Moreover, by experimental study of the different pre-wetted time conditions on working performance, a reasonable pre-wetted time of ceramsite before ceramsite aggregate concrete for construction is summarized as well.
Abstract: We researched the effect of single intrinsic defect of the structure and electronic properties of V-doped ZnO. After vanadium (V) atom replaced one zinc atom, lattice constants and bulk modulus increased slightly 1.2% and as high as 8.9%, respectively. The total energy showed that oxygen defect inclined to stay at a position far from V atom but zinc defect likely to localize at a position near V atom. The electronic density state of pure ZnO was semiconductor behavior. Vanadium doping introduced a spin-polarization around Fermi-level. The 3d orbital of V split into triplet-state ta (antibonding state), dual-state e (nonbonding state) and triplet-state tb (bonding state) in the wurtzite ZnO crystal field. The ta state hybridized with O2p state above Fermi-level, which made Zn15VO16 underwent a semiconductor-halfmetal transition. Vanadium substitution moved the electronic density states to lower energy. Oxygen defect had little effects on V-doped ZnO while zinc defect moved the density of states to higher energy. Our paper provided a reference for the preparation and application of V-doped ZnO.
Abstract: Based on the analysis of current developing state of graph theory, define the description of spacial moving capability of common couples and translation base and rotation base of mechanism, based on the new description method in topological graph theory. DOF(degree of freedom) of hybrid mechanism analysised with example based on the definition of dimensionity of branch spacial moving capability and mechanism spacial moving capability, necessary and sufficient condition of nonsingularity of mechanism presented, as well as the necessary and sufficient condition of singularity of mechanism deduced , in-phase and assimilation condition and in-phase and dissimilarity condition and asynchronism condition of limitation of input base of branch adopted, case number of position singularity and pose singularity and position and pose singularity obtained then, still the way of founding the combination and case number of common serial mechanism and parallel mechanism and hybrid mechanism mentioned.
Abstract: There are two kinds of charges in dielectric materials, one is bound charge, and the other is free charge. Bound charge will introduce dielectric relaxation under applied AC electric field, which will be detected with dielectric spectroscopy. Free carrier will introduce DC conduction through the sample from one electrode to the other under DC electric field. But what can we do to obtain AC and DC properties of dielectric materials at the same time? In this paper, dielectric characteristics of ZnO varistor ceramics in a wide range of frequency and temperature are reported. DC conductivity is observed at low frequency and high temperature region and grainboundary Schottky barrier is obtained further. Dielectric loss peaks are observed at high frequency and low temperature region and single grainboundary electric breakdown voltage is calculated. At the end of the paper, the advancing trend of dielectric spectroscopy is discussed.
Abstract: Styrene butadiene rubber (SBR)/clay/carbon black (CB) nanocomposites filled with 60 phr filler (in total) were prepared by adding CB to SBR/clay nanocompound in a two-roll mill. TEM photographs of the nanocomposites showed that both fillers were dispersed randomly in the SBR matrix at nano-scale. With the increase of CB content, stress at 300% strain and tensile strength of the nanocomposites increased, while elongation at break and permanent set of the nanocomposites decreased. On the other hand, with the increase of clay content, the aging resistance of the SBR nanocomposites was improved.
Abstract: The reactions were carried out by decomposing acetylene at 1000 °C in a two-stage furnace system for 10 min. In the first furnace no catalyst was placed and an AAO template with average diameter about 50 nm was placed in the second furnace whose temperature was designed to be 700 °C. The samples were characterized by scanning electron microscopy and high resolution transmission electron microscopy. The results show that carbon spheres with average diameter about 50 nm on the AAO template surface were obtained and these carbon spheres are composed of unclosed graphene layers with an interlayer distance of 0.33–0.35 nm between the layers.
Abstract: The study on deformation in impact-damaged graphite-fibre/epoxy stitched composite plates subjected to compressive load is presented. A delaminated cross-ply laminate [03/903]S obtained in low-velocity impact test has been examined using a self-designed anti-buckling device in compressive experiment. The out-of-plane displacement field of the specimen has been measured with an optical whole-filed measurement technique, which is carrier electronic speckle pattern interferometry (carrier-ESPI). Finite element (FE) simulation is also carried out to predict the deformation. The effect of the stitching line on compressive deformation is discussed for various stitched laminates. Finally, the numerical results are compared with experimental measurement deformations under different compressive loads.