Analysis and design of the force and displacement transmissibility of nonlinear viscous damper based vibration isolation systems

This study is concerned with the analysis and design of the force and displacement transmissibility of nonlinear viscous damper based vibration isolation systems. Analytical algorithms are derived using the Ritz–Galerkin method to evaluate the transmissibility of SDOF displacement vibration isolation and force vibration isolation systems where a nonlinear viscous damper is used as an energy dissipating device. The results reveal that compared to linear dampers, nonlinear viscous dampers can more significantly improve the system vibration isolation performance in a wider frequency range. A procedure is then proposed based on the analysis results to facilitate the design of nonlinear viscous dampers for system vibration isolation purposes. These results have significant implications for the design of vibration isolation systems in many engineering applications.     

A Volterra series approach to the frequency domain analysis of non-linear viscous Burgers’ equation

In this paper, higher order frequency response functions, based on the Volterra series, are employed to characterise the input-output behaviour of the non-linear viscous Burgers?? equation subject to sinusoidal excitation. First, a formal Volterra series representation for each spatial location is derived for the solution of Burgers?? equation with a boundary condition as the input to the system. Then a systematic method is presented to obtain the higher order frequency kernels of the Volterra series at each spatial location by solving a series of ordinary differential equations. It is shown that the convergence region of the individual harmonics with respect to the magnitude of the input excitation can be estimated by using these higher order kernels. The frequency characteristics of Burgers?? equation is investigated and compared with numerical simulation.     

汽车车身油漆红外光谱特征

采集了287份汽车车身油漆样本,使用傅里叶变换显微红外光谱仪获取了940份油漆层光谱,对不同车型、颜色的汽车油漆的清漆层、面漆层、中涂层的光谱特征进行分析,并对其光谱相似度进行比较。结果表明,同车型不同颜色的清漆层光谱相似度达到99.5%,部分相近车型的清漆层光谱高度相似;面漆层光谱因车型、颜色不同而差异较大,相似度在70%以下;中涂层的普通腻子光谱间的相似度在83.33%～96.91%,水基腻子光谱间的相似度在70.12%～96.44%;油漆中的金属成分会影响面漆层光谱的吸收特征;汽车油漆光谱随使用时间变化而发生变化。     

Preparation and Supercapacitive Properties of Fe2O3/Active Carbon Nanocomposites

Fe₂O₃/active carbon(Fe₂O₃/AC) nanocomposites were readily fabricated by pyrolyzing Fe³⁺ impregnated active carbon in a nitrogen atmosphere. The as-prepared composites were studied by X-ray powder diffraction(XRD), X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(TEM). The capacitive property of the composites was investigated by cyclic voltammetry(CV) and galvanostatic charge-discharge test. Physical characterizations show that the γ-Fe₂O₃ fine grains dispersed in the AC well, with a mean size of 21.24 nm. Electrochemical tests in 6 mol/L KOH solutions indicate that the as-prepared nanocomposites exhibited improved capacitive properties. The specific capacitance(SC) of Fe₂O₃/AC nanocomposites was up to 188.4 F/g that was derived from both electrochemical double-layer capacitance and pseudo-capacitance, which was 78% larger than that of pristine AC. A symmetric capacitor with Fe₂O₃/AC nanocomposites as electrode showed an excellent cycling stability. The SC was only reduced by a factor of 9.2% after 2000 cycles at a current density of 1 A/g.     

Output frequency properties of nonlinear systems

Nonlinear systems usually have complicated output frequencies. For the class of Volterra systems, some interesting properties of the output frequencies are studied in this paper. These properties show theoretically the periodicity of the output super-harmonic and inter-modulation frequencies and clearly demonstrate the mechanism of the interaction between different output harmonics incurred by different input nonlinearities in system output spectrum. These new results have significance in the analysis and design of nonlinear systems and nonlinear filters in order to achieve a specific output spectrum in a desired frequency band by taking advantage of nonlinearities. Examples and discussions are given to illustrate these new results.     

Interfacial stress transfer behavior in a specially-shaped fiber/matrix pullout test

Specially designed fibers are widely used in engineering practice because the specially-designed shape can help to improve the bonding strength of the fiber and the interface. Studied in this paper is the interfacial shear stress transfer behavior on both sides of the specially designed fiber when it is being pulled out; in which automatic analysis of three-dimensional photoelasticity is employed and the finite element method is adopted. The results show that the stress transfer occurs mainly in the region near the fiber＇s embedded end where the stress reaches its critical point, leading to debonding of the interface. Before debonding, as the pullout loading increases, the peak value of shear stress transfers along the fiber from the embedded end to the interior of the matrix, and then stops at the hooked part of the fiber because of its impediment. When the interface begins to debond as the load increases, the shear stress can be transferred to the hooked part.     

有机盐制备的Fe3O4-葡聚糖纳米粒子的磁性能及表征

By means of chemical co-deposition method in which added Ferric citrate and Ferrous Gluconate, Fe3O4-Dextran composite nano-particles having average diameter 26 nm, was obtained. The particles had a core of diameter 4.1 nm Fe3O4 with a shell of thickness 11 nm Dextran. In the experiment the critical structure of Fe3O4 inorganic particles abstained without N2 protection had no changes. From the result, it can be proven that organic salt has anti oxidation properties and the composite particles have superparamagnetic whose good magnetization is 52 emu/g at 300 K, and 63 emu/g at 5 K. The structure, pattern diameter and magnetic properties of the Fe3O4-Dextran composite particles were examined by means of TEM, XRD, DLS and VSM.     

Effect of dust charge variation on dust—acoustic solitary waves in a magnetized two—ion—temperature dusty plasma

The effect of dust charge variation on the dust-acoustic solitary structures is investigated in a warm magnetized two-ion-temperature dusty plasma consisting of a negatively and variably charged extremely massive dust fluid and ions of two different temperatures. It is shown that the dust charge variation as well as the presence of a second component of ions would modify the properties of the dust-acoustic solitary structures and may exite both dust-acoustic solitary holes (soliton waves with a density dip) and positive solitons (soliton waves with a density hump).     

乙烯渣油沥青基活性炭纤维和粘胶基活性炭纤维的表面性质与脱硫活性

研究了在O2和H2O存在下,乙烯渣油沥青基活性炭纤维(ETPACF)和粘胶基活性炭纤维(CelluloseACF)的脱硫活性.结果表明,在比表面积相近的情况下,ETPACF的脱硫活性明显低于CelluloseACF,这可归因于后者具有较强的吸附和催化氧化SO2能力及较大的吸水量,尤其是具有较强的催化氧化SO2的能力,这些能力又与其表面含有含氮官能团以及某些含氧官能团有关,因此ACF的表面官能团对其脱硫活性影响很大.     

Performance Optimization for the Parallel Gauss–Seidel Smoother

Simulation, e.g., in the field of computational fluid dynamics, accounts for a major part of the computing time on highperformance systems. Many simulation packages still rely on Gauss–Seidel iteration, either as the main linear solver or as a smoother for multigrid schemes. Straight-forward implementations of this solver have efficiency problems on today's most common high-performance computers, i.e., multiprocessor clusters with pronounced memory hierarchies. In this work we present two simple techniques for improving the performance of the parallel Gauss–Seidel method for the 3D Poisson equation by optimizing cache usage as well as reducing the number of communication steps. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)