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| 1 | Analysis and Numerical Simulation of Rolling Contact between Sphere and Cone显示文摘In non-conforming rolling contact, the contact stress is highly concentrated in the contact area. However, there are some limitations of the special contact model and stress model used for the theoretical study of the phenomenon, and this has prevented in-depth analysis of the associated friction, wear, and failure. This paper is particularly aimed at investigating the area of rolling contact between a sphere and a cone, for which purpose the boundary is determined by the Hertz theory and the geometries of the non-conforming surfaces. The phenomenon of stick-slip contact is observed to occur in the contact area under the condition of no-full-slip(Q < μ·P). Using the two-dimensional rolling contact theory developed by CARTER, the relative positions of the stick and slip regions and the distribution of the tangential force over the contact area are analyzed. Furthermore, each stress component is calculated based on the Mc Ewen theory and the idea of narrow band. The stress equations for the three-dimensional rolling contact between the sphere and the cone are obtained by the principle of superposition, and are used to perform some numerical simulations. The results show that the stress components have a large gradient along the boundary between the stick and slip regions, and that the maximum stress is inversely proportional to the contact coefficient and proportional to the friction coefficient. A new method for investigating the stress during non-classical three-dimensional rolling contact is proposed as a theoretical foundation for the analysis of the associated friction, wear, and failure. | ZHAO Yanling XIA Chengtao WANG Hongbo XUAN Jiaping XIANG Jingzhong LIU Xianli SU Xiangguo | 2015 | Chinese Journal of Mechanical Engineering2015，28，3： | 18 |
| 2 | Comparative urbanization of birds in China and Europe based on birds associated with trees显示文摘Urbanization effects on living organisms are spatially heterogeneous.Here we quantified the abundance of birds per tree in forested urban and rural habitats for 85,829 trees mainly in China and Europe.A population model was based on the assumption that:1)birds have a normally distributed habitat preference;2)an increase in population size linked to the habitat preference;3)a population size dependent on the habitat preference;and 4)the removal of a certain fraction of individuals giving rise to extinction.We tested for large-scale differences in the impact of urbanization on the frequency distribution of the difference in abundance between urban and rural habitats in China and parts of Europe.The difference in the frequency distribution of urban population density of birds in trees minus rural population density of birds in trees in China and Europe was statistically significant suggesting that the abundance of birds differed between trees in urban and rural habitats,but more so in China than in Europe.We hypothesize that more pronounced differences in China than in Europe may have arisen due to the Four Pests Campaign in 1958-1962 that resulted in death of hundreds of millions of birds(mainly tree sparrows Passer monfanus,but also numerous other less common species that were starting to become urbanized around 1960).Species that were less common in 1960 could not sustain reductions in population size in urban areas and hence these species are still rare or absent in urban areas today 60 years later. | Anders Pape MOLLER Canwei XIA Bo ZHOU Xianli CHE Xingzhi CHE Changzhang FENG Karsten LAURSEN Federico MORELLI Wangming LI Jianping LIU Qing QUAN Min ZHANG Qiang ZHANG Qiangwen ZHAN Laikun MA Haitao WANG Fasheng ZOU Wei LIANG | 2019 | Current Zoology2019，65，6： | 0 |
| 3 | East Asian Winter Monsoon record from the environmental sensitive grain size component of QF Old Red Sand, Haitan Island, China显示文摘The 'Old Red Sand' is widely distributed along the coast of Fujian Province, China. Most studies have been carried out from aspects of the origin, age and laterization of the 'Old Red Sand', but this paper focused on reconstructing the history of the Asian Winter Monsoon change. On the basis of granulometric analysis of high-resolution samples, we have obtained environmental sensitive grain size component (ESGSC) from the Qingfeng (QF) profile by using the grain size-standard deviation method, which proves that the selected ESGSC is an important climate proxy. The mean grain size of this ESGSC could be used to reconstruct the East Asian Winter Monsoon (EAWM) intensity. As such, the history of the EAWM change since 44.0 ka reconstructed here reveals three main phases based on chronology dates of previous researches: (1) 44.0-25.5 ka B.P., the EAWM is relatively weak but increases gradually with fluctuations; (2) 25.5-15.5 ka B.P., relatively strong with high frequency fluctuations; (3) 15.5-7.1 ka B.P., with a weaker winter monsoon, but during 11-10 ka B.P. is remarkably enhanced. The EAWM recorded by mean grain size of the two neighboring sections have a better repeatability, so the millennial scales oscillation should be a reliable signal of the EAWM intensity. The climate recorded by ESGSC of the QF 'Old Red Sand' compared to δ 18 O of Hulu Cave stalagmites and Greenland GISP2 ice cores shows a good consistency, especially in detail, the YD event and four Heinrich events are all recorded, but the signal of D-O cycles was relatively weak. | FanGen Hu ZhiZhong Li JianHui Jin Qian Zhao Hui Zhang XianLi Wang Jing Xia | 2013 | Research in Cold and Arid Regions2013，5，2： | 0 |
| 4 | On the Consumption Structure of Rural Residents in Xi'an City Based on AIDS Model显示文摘Under the background of the financial crisis,expanding domestic demand for stimulating economic role is self-evident. As China has a large rural population,increasing rural residents' income and expanding their consumer demand is becoming the pinnacle of expanding domestic demand. The urban residents have good conditions than more countryside dwellers. Since few articles are dedicated to the research of this group,this article selects rural residents of Xi'an as object,uses AIDS model to analyze the consumption structure of rural residents,and draw the conclusion that increasing cultural recreation,medical and health spending is the main way to increase their incomes. | Shuanghong TANG Xianli XIA | 2015 | Asian Agricultural Research2015，7，1： | 0 |
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