Abstract Based on theory of dissolution and dispersion and special chemical structure of vegetable oil, the article chooses four kinds of vegetable oil (Tung oil, Castor oil, Rapeseed oil and Linseed oil) and blended them with asphalt. And then Rejuvenating Agents of asphalt based on the four kinds of vegetable oil are prepared. The test results show that good exponent relationship is presented between Tung oil content and Brookfield viscosity of Tung-oil-based Rejuvenating Agent. Furthermore, this paper studies the performance of recycled asphalt by conventional indexes, adhesion, SHRP indexes. The data show it by improving the composition of aging asphalt, thereby enabling recycled asphalt indexes recovered to close to or above the level of original asphalt.
Under low-temperature conditions in winter, asphalt pavement is prone to cracking, icing and other distresses, which affect its safety and comfort. Therefore, by incorporating phase-change materials into asphalt and conducting relevant performance studies, the aim is to alleviate low-temperature distress and regulate road surface temperature and expand the application of phase-change materials in asphalt pavement. We mixed the selected phase-change materials with different dosages into the matrix asphalt to prepare phase-change temperature-regulating asphalt and tested the four basic indicators: road performance, latent heat characteristics, temperature-regulating performance, and rheological properties of phase-change asphalt and its mixture. The research results indicate that with the increase in phase-change material content, the penetration, softening point, ductility, and dynamic viscosity of phase-change high-viscosity asphalt gradually increase. Under the constant temperature test conditions of −2.5 °C and −5 °C, the surface icing speed of asphalt binder specimens mixed with phase-change materials is slower than that of specimens without phase-change materials. Adding phase-change materials can improve the high-temperature and low-temperature PG grading of high-viscosity asphalt, effectively improving its high-temperature rutting resistance and low-temperature cracking performance. According to the temperature regulation test results, phase-change temperature-regulating asphalt has a certain regulating effect on temperature under low-temperature conditions, which can slow down the cooling rate of asphalt, reduce the thermal conductivity of permeable asphalt mixture by more than 50%, increase the temperature regulation rate by more than 30%, and improve the ice-melting and snow-melting ability by more than 20%. Phase-change materials have almost no effect on the porosity of permeable asphalt mixtures and can effectively improve the water stability, low-temperature crack resistance, and antiflying performance of permeable asphalt mixtures. Their Marshall stability and rutting stability decrease, but still meet the requirements of the specifications. Applying phase-change materials to permeable asphalt pavement can automatically adjust the temperature of the pavement, reduce the cooling rate of the asphalt pavement during cooling, alleviate the problem of snow and ice accumulation on the asphalt pavement in winter, and thereby improve the performance of permeable asphalt pavement against freeze–thaw cycles.
An overview of the mechanisms for mechanofluorochromic behaviors based on organic/polymer systems has been provided, and the most significant developments in understanding the origin of mechanofluorochromism have been highlighted. The views are mainly focused on the intermolecular effects and intramolecular effects on mechanofluorochromism, including excimer forming, phase structural transition, J- or H-aggregation and intramolecular coplanarity and so on. It should be helpful to researchers to understand more deeply the relationships between the molecular structures and the mechano-responsive behaviors.
An object-oriented finite-difference time-domain (FDTD) simulator has been developed for electromagnetic study and design applications in Magnetic Resonance Imaging. It is aimed to be a complete FDTD model of an MRI system including all high and low-frequency field generating units and electrical models of the patient. The design method is described and MRI-based numerical examples are presented to illustrate the function of the numerical solver, particular emphasis is placed on high field studies.
This article,through summarizing the progresses in the evapotranspiration(ET0) methods research,analyzes representative ET0 computation methods emphasized on three periods of the world: modificative Penman(MP),Penman-Monteith(PM) and standard ASCE-PM.We take 20th century 90's last stages and 21th century initial period′s world newest 19 experimental achievements with lysimeter′s actual value rating ET0 value as the foundations,analyzing general usage of the ET0 computational method regarding the different climatic conditions.Although the effect of PM method application is desirable in many areas,many local effects are still unsatisfactory;the method MP and so on are more suitable in part of areas;the PM and MP method are not popular,the special attention must be paid to the standard ASCE-PM method.In brief,these kinds of half theory (semi-empirical) methods only suit in certain areas.By comparison of MP and PM method,we can′t simply evaluate which kind of method is superior or which kind of method calculates the ET0 value big(or value is small),and we should consider different geography,the climatic conditions and lysimeter experimental result.In the article,there is also corresponding suggestion for the research in the future,which is helpful to the thorough research of ET0 method discipline.
The mass ratio of Ca to Sr is greater than 10 in Nanyishan oil-field water, which causes significant problems during the economic extraction and recovery of selected trace elements in the oil-field water. The oilfield water was isothermally evaporated and various salts such as Li, K, Mg, Ca, Na, Sr, Rb, Cs, Br, and I were obtained from the solution. The Sr content of each phase was determined by ICP-AES, the Sr distribution rule in this process was obtained, and the best separation stage for Sr was identified, to optimize the separation of Sr from Nanyishan oil-field water.
There is an increasing requirement of using porous asphalt as overlay of old pavement in maintenance engineering. It is important to study the mechanical property of the road structure with porous asphalt overlay. In this research, old road surface in different conditions are taken into account, including: pavement with different rutting depth and hot in-place recycled surface. Continuous loading measurements and rotary loaded wheel tests were performed on the core samples and cores paved with porous overlay. Finite element method was employed to simulate deformation of the road structure. It shows that the bearing capacity and rutting resistance are improved by adding the porous asphalt layer in general. The milled thickness of the original road surface layer also influences performance of the whole structure. This research can help engineers to make road structural design by using porous asphalt overlay in pavement maintenance and reconstruction.
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