掺钯碳纳米管的制备及电接触性能

以PbCl₂为介质, 采用无电沉积方法制备了掺钯碳纳米管, 并对其形貌和结构进行了表征. 结果表明, 掺入的钯纳米粒子分布均匀、 粒径均一, 掺杂量与粒径尺寸适中; 所掺入的纳米粒子的成分为0价态的钯, 且掺杂类型为p型. 电接触性能测试结果表明, 掺钯碳纳米管与金电极间的接触电阻得到了明显改善, 阻值平均降幅高达近71.09%.     

A modification of the factorization method for scatterers with different physical properties

We study an inverse acoustic scattering problem by the factorization method when the unknown scatterer consists of two objects with different physical properties. Especially, we consider the following two cases: One is the case when each object has the different boundary condition, and the other one is when different penetrability. Our idea here is to modify the far‐field operator depending on the cases to avoid unnecessary a priori assumptions.     

Time domain finite volume method for three-dimensional structural–acoustic coupling analysis

This work extends the application of finite volume method (FVM) to structural–acoustic problems. A three-dimensional time domain FVM (TDFVM) is proposed to predict the transient response and natural characteristics of structural–acoustic coupling systems. Acoustic wave equation in heterogeneous medium and structural dynamic equation are solved in fluid and solid sub-domains respectively. The structural–acoustic coupling is implemented according to normal components of particle acceleration continuity condition and normal traction equilibrium condition at the interface. The computational domain is discretized with four-node tetrahedral grid which is generated easily and has strong adaptability to complicated geometries. Numerical experiments are carried out to examine the accuracy of the method in both time domain and frequency domain. The results show good agreement with analytical solutions and numerical results. For structural–acoustic problem, TDFVM has the capability to consider the heterogeneity of both fluid and solid.     

Analysis of multiple wavelengths of Lamb waves generated by meander-line coil EMATs

The electromagnetic acoustic transducers (EMATs) with a meander-line coil possess the capability of generating Lamb waves carrying multiple wavelengths, and the characteristics of multiple wavelengths is analyzed by developing a spatial transversal filter model for the EMAT. It is shown that the characteristics is due to the wavelength spectrum of the EMATs, which is a wavelength-domain representation of information about the wavelength components, and the magnitude of each components is modulated by an envelope which depends on the geometric pattern of the meander-line coil. The characteristics of multiple wavelengths might cause the multi-modes phenomenon, therefore a method for removing the effect of multiple wavelengths is proposed. It is shown that the effect can be removed by designing an EMAT which can produce a special envelop to suppress the harmonic wavelengths. Experiments are set up to study the characteristics of multiple wavelengths and verify the validity of the proposed method.     

Flow-induced noise analysis for 3D trash rack based on LES/Lighthill hybrid method

A trash rack is used to obstruct dirt in a flow. As it is on the outside of the hull of a ship, such flow-induced noise cannot be ignored. This paper focuses on a hydrodynamic noise study of the trash rack installed on the inlet of pipelines to estimate the noise produced by the turbulent flow. A hybrid method of combining Large-Eddy Simulation (LES) and the Lighthill’s acoustic analogy theory simulate the flow-induced noise for a three-dimensional pipeline. The results of the simulation agree well with the experimental results available in the open literature. Following this, the hydrodynamic noise of flow through a three-dimensional pipeline with different types of trash racks is studied in order to determine the best form. For this objective, the flow and sound properties in different simulation models are analyzed and a low noise type of trash rack is proposed based on some general indexes.     

Photophysical and nonlinear optical properties of an azobenzene substituted zinc phthalocyanine

Photophysical property and third-order optical nonlinearity of an azobenzene substituted zinc phthalocyanine (azo-ZnPc) in chloroform solution were studied by UV–Vis spectra method and a picosecond Z-scan technique at 532 nm with pulse duration of 25 ps, respectively. It was found that the azo-ZnPc shows large positive nonlinear refraction and positive nonlinear absorption, exhibiting the defocusing effect and reverse saturable absorption, respectively. The molecular second hyperpolarizability of the azo-ZnPc dyad was measured to be 3.9 × 10⁻³⁰ esu. All the results suggest that the studied azo-ZnPc dyad may have potential applications in the field of nonlinear optics.     

Toward a reduction of mesh imprinting

This paper is the initial investigation into a new Lagrangian cell‐centered hydrodynamic scheme that is motivated by the desire for an algorithm that resists mesh imprinting and has reduced complexity. Key attributes of the new approach include multidimensional construction, the use of flux‐corrected transport (FCT) to achieve second order accuracy, automatic determination of the mesh motion through vertex fluxes, and vorticity control. Toward this end, vorticity preserving Lax–Wendroff (VPLW) type schemes for the two‐dimensional acoustic equations were analyzed and then implemented in a FCT algorithm. Here, mesh imprinting takes the form of anisotropic dispersion relationships. If the stencil for the LW methods is limited to nine points, four free parameters exist. Two parameters were fixed by insisting that no spurious vorticity be created. Dispersion analysis was used to understand how the remaining two parameters could be chosen to increase isotropy. This led to new VPLW schemes that suffer less mesh imprinting than the rotated Richtmyer method. A multidimensional, vorticity preserving FCT implementation was then sought using the most promising VPLW scheme to address the problem of spurious extrema. A well‐behaved first order scheme and a new flux limiter were devised in the process. The flux limiter is unique in that it acts on temporal changes and does not place a priori bounds on the solution. Numerical results have demonstrated that the vorticity preserving FCT scheme has comparable performance to an unsplit MUSCL‐H algorithm at high Courant numbers but with reduced mesh imprinting and superior symmetry preservation. Copyright © 2014 John Wiley & Sons, Ltd.     

Mesomorphic properties of a tetraphenylporphyrin metallomesogen with a weak hydrogen bond interaction between axial ligands: dihydroxo[5,10,15,20-tetrakis(4-n-dodecylphenyl)porphinato]silicon(IV)

A new metallomesogen, the dihydroxo[5,10,15,20-tetrakis(4-n-dodecylphenyl)porphinato]silicon(IV) complex, C₁₂TPPSi(OH)₂, was synthesized and its mesomorphism was investigated in terms of the axial hydrogen bond interaction in the stacked columnar structure. It was found that this compound exhibits a 3D plastic lamellar mesophase with a columnar structure, and the axial hydroxyl groups are connected by a very weak hydrogen bond interaction in the column. This causes a dramatic increase of the clearing point for the mesophase, even though the stacking periodicity is far larger (c. 9?Å) than that typically found for a columnar meosphase (c. 3.5?Å).