Viscoelastic model for asphalt mixture under repeated haversine load

The series-wound dashpot of the Burgers model is modified by introducing the strain hardening parameter, and the new model is considered as a combination of the modified dashpot and the Van Der Poel model. The cyclical pulse load consisting of a haversine load time and a rest period is adopted to simulate the actual vehicle load, and the permanent strain model under the repeated load is derived from the rheological and viscoelastic theories. Subsequently, the model is validated by the results of uniaxial repeated load permanent deformation tests of three asphalt mixtures. It is indicated that the proportion of residual viscoelastic strain to permanent strain decreases gradually with the load cycles, and only accounts for 2% to 3% during most of the loading period. If the rest period is long, the residual viscoelastic strain is little. The rest period of the actual vehicle load may be long enough, so the residual viscoelasticity can be ignored and the simplified model can be obtained. The proposed model can well describe the permanent deformation of asphalt mixtures under repeated load.

Attenuation of wave propagation in a novel periodic structure

A novel periodic mount was presented. A theoretical model was developed to describe the dynamics of wave propagation in the novel periodic mount. The model was derived using Hamilton's energy conservation principle. The characteristics of wave propagation in unit cell were analyzed by transfer matrix formulation. Numerical examples were given to illustrate the effectiveness of the periodic mount. The experiments were carried out to identify the predications of the theoretical model. The obtained results show that the experimental results coincide with the prediction of theoretical model. No pass bands appear in the overall frequency range measured when waves propagate in the longitude direction of the periodic mount. These dramatic results demonstrate its potential as an excellent mount in attenuating and isolating vibration transmission.

Equatorial Rossby Solitary Wave Under the External Forcing

A simple shallow-water model with influence of external forcing on a β-planeis applied to investigate the nonlinear equatorial Rossby waves in a shear flow. By theperturbation method, the extended variable-coefficient KdV equation under an external forcing isderived for large amplitude equatorial Rossby wave in a shear How. And then various periodic-likestructures for these equatorial Rossby waves are obtained with the help of Jacobi ellipticfunctions. It is shown that the external forcing plays an important role in various periodic-likestructures.

A Model for Periodic Nonlinear Electric Field Structures in Space Plasmas

In this study,we present a physical model to explain the generation mechanism of nonlinear periodic waveswith a large amplitude electric field structures propagating obliquely and exactly parallel to the magnetic field.The'Sagdeev potential' from the MHD equations is derived and the nonlinear electric field waveforms are obtained when theMach number,direction of propagation,and the initial electric field satisfy certain plasma conditions.For the parallelpropagation,the amplitude of the electric field waves with ion-acoustic mode increases with the increase of initial electricfield and Mach number but its frequency decreases with the increase of Mach number.The amplitude and frequency ofthe electric field waves with ion-cyclotron mode decrease with the increase of Mach number and become less spiky,andits amplitude increases with the increase of initial electric field.For the oblique propagation,only periodic electric fieldwave with an ion-cyclotron mode obtained,its amplitude and frequency increase with the increase of Mach number andbecome spiky.From our model the electric field structures show periodic,spiky,and saw-tooth behaviours correspondingto different plasma conditions.

Comparison between the preparation,structure and mechanical properties of long fiber reinforced thermoplastics and short fiber reinforced thermoplastic

This article summarizes the comparison between the preparation, structure and mechanical properties of long fiber reinforced thermoplastics （LFT） and short fiber reinforced thermoplastics （SFT）. Both of the experiment and theory results showed that the mechanical properties of long glass fiber reinforced thermoplastics pellets （LGFRT） have been enhanced better than that of short glass fiber reinforced thermoplastics pellets （SGFRT） manufactured by molding procession. After regulation of the relative humidity by 50 % , the mechanical properties of 30 % （ weight percent） short glass fiber content in SFT （ SFT-PA6-SGF30 ） are similar to that of 40 % long glass fiber content in LFT. Howev- er, the density of the latter is about 17 % lower than that of the former. Thus, the corresponding weight of products is reduced by 13 % ;output rate is increased by 21% , and the cost is therefore significantly lowered. And it has the fol- lowing advantages： impact strength is increased by 87 % ; the proportion is reduced by 20 % ; molding cycle is short- ened by 10 % ;materials cost is saved by 20 % -30 % and the final total cost is saved by 30 % -40 %. So LFT （LFT-PP-LGF40） can replace SFT （SFT-PA6-SGF30） with the similar basic mechanical properties under normal tem- perature or 160 ℃ lower.

椭圆相对运动方程的高阶分析解

相对动力学的研究在编队飞行应用中非常重要,比较精确的编队构型可以较大程度地减少队形保持所需的燃料消耗.传统的构型设计主要基于线性化方程即C-W方程(圆参考轨道)或Lawden方程(椭圆参考轨道)的周期解.可是,线性化解在编队尺度较大时不再适用.鉴于此,本文以椭圆参考轨道对应的非线性相对运动方程为基础,将伴星相对于主星的相对运动展开为参考轨道偏心率、平面内振幅以及垂直平面振幅的级数解形式,并以Lawden周期解为初始解,采用Lindstedt-Poincar′e方法构造任意高阶的分析解.特别地,本文构造的分析解在参考轨道偏心率为零时,可退化描述圆参考轨道对应的周期构型.最后,为了验证分析解的有效性,计算了分析解对应的收敛域.

Current Situation and Prospects for the Urbanization of Chinese Migrant Workers

This article uses the age-structure/life-cycle method to analyze the impact of migrant workers’ employment on their urbanization. Since enterprises tend to employ younger workers and unemployed migrant workers tend to be middle-aged, we first apply the age structure/life cycle model to carry out our estimations, pointing out that in order to complete the urbanization of their families, migrant worker couples usually have to work for thirty years consecutively after marriage. On this basis, the article constructs a working life table for migrant workers and uses it to estimate the total quantity of Chinese migrant workers who have the minimum economic capacity required for urbanization. Taking into consideration future changes in the age structure of enterprise employment, we estimate that over the sixty-nine million migrant workers who were under thirty years old in 2006, together with their families, would already be in possession of the minimum economic conditions for settling in urban areas.