Road condition surveys show that the long and steep climbing section of asphalt pavement is one of the regions with the most significant rutting that seriously affects the road performance. And rutting is more serious for steeper longitudinal slope. In this paper, the changing rule of shear stress and its distribution characteristics in pavement are analyzed on conditions of different longitudinal slope and different horizontal attachment coefficients by a finite element method. The results show that the maximum shear stress is less subjected to the component of gravity when the longitudinal gradient changes. Due to the existence of longitudinal gradient, the changes of the adhesion between tires and road affect the shear stress significantly. The peak maximum shear stress gradually moves to the surface with increasing the horizontal force coefficient. The research results presents guides on how to prevent and control distresses for asphalt pavements on a long and steep slope.
In this paper, the microscopic mechanism of rutting formation is studied by the Discrete Element Method (DEM). The particles in discontinuous asphalt mixtures are discretized into circular rigid particles by DEM, then the initial model is created in accordance with the actual pavement. The displacement vector changes of particles under loading and the process of rutting formation are presented in this paper. The asphalt pavement model has been built to simulate the material properties of asphalt pavement by the PFC2D software. At the same time, the displacement vector changes in each layer have been analyzed under loading. In addition, the mechanisms of permanent deformation have been studied and the rutting formation process of asphalt pavement has been simulated. The results show that the Discrete Element Method used to study permanent deformation characteristics of asphalt pavement is reasonable and feasible.
Room-temperature contactless electroreflectance (CER) was used to investigate the optical properties of a N,N'-didecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C10H21) thin-film sandwiched between indium tin oxide and aluminum electrodes (Al/PTCDI/ITO/glass substrate) under vacuum conditions. The electromodulated optical responses of the Al/PTCDI/ITO/glass structures were characterized by various alternating current biases. The optical transitions of PTCDI were perturbed by energy shifts of electronic states due to the Stark effect induced by the modulated electric field. The modulated CER spectrum of PTCDI is strongly enhanced by performing first derivatives on the absorption spectrum of PTCDI. The CER spectrum involves fundamental transitions, doping states, and Davydov splitting. Moreover, the intensity of the field-induced transition peak of PTCDI increases with increasing CER modulation voltage. The transition energies between the lowest unoccupied molecular orbital and highest occupied molecular orbital of the Al/PTCDI/ITO system is obtained from the peak positions in the CER spectrum.
As general practice, Poly(3,4-ethylenedioxythiophene):Polystyrene Sulfonate (PEDOT:PSS) is the most widely used conducting polymer as electrode material in organic (polymer) devices. PEDOT: PSS film is fabricated by solution processes such as spin-coating, dip-coating, inkjet printing (IJP), contact printing, etc. One of the most complex operations in the fabrication process is forming conduction electrode lines or isolate devices from each other with the pattern of polymeric film IJP, which is a non-impact printing technology in which droplets of ink are jetted directly on a media to create a pattern. In this paper, PEDOT:PSS films, prepared by inkjet-printing and spin-coating methods, have been studied by using atomic force microscopy (AFM), micro-Raman spectroscopy and photoelectron spectroscopy measurements (PL). PEDOT:PSS films formed with the inkjet-printing method are appropriate for using as an anode for simplification of the fabrication process of polymer light-emitting diodes whose performance is about 1.2 cd/A. The performance is the same as spin-coating method. The performance was attributed to longer effective conjugation length of PEDOT chains in inkjet-printing PEDOT:PSS films, as suggested by their micro-Raman spectroscopy.
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